feat(ext-jackson): one module per data format, bodies checked on the way in

flash-ext-jackson and flash-ext-validation become three modules: - flash-ext-jackson-core: the Codec (one mapper, body/write/writeView), JacksonHandler, the outbound marshalling, and the constraint engine that used to be flash-ext-validation - flash-ext-jackson-json: Json, JsonExtension, JsonHandler - flash-ext-jackson-xml: Xml, XmlExtension, XmlHandler Every Jackson format is the same databind model behind a different factory, so the annotations, the constraints and the published schema are the same for all of them: only the mapper and the content type differ, and that is all a format module says. A route picks its format by the handler it extends — there is no negotiation and nothing to configure. A typed body is now always verified against its own type's jakarta constraints, whatever the format: malformed is a 400, a broken constraint is a 422, and neither reaches the handler. The validator was already allocation-free and stays so; validating is no longer something an application remembers to do. bodyFrom is gone. body has the streaming semantics, because the request's stream is reused per connection while bytes() allocates the whole body: one name, the path that does not allocate. JacksonExtension is JsonExtension, and autoJson() is auto(). The root POM now manages every module of this build, so anything composing Flash imports it once and never names a version again. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-23 13:31:28 +00:00
parent ef4740f26d
commit adcd6376b6
37 changed files with 894 additions and 801 deletions
@@ -0,0 +1,66 @@
+# flash-ext-jackson-core
+
+What every Jackson data format shares. Applications do not install this module directly: they
+install a format — [`flash-ext-jackson-json`](../flash-ext-jackson-json),
+[`flash-ext-jackson-xml`](../flash-ext-jackson-xml) — and get all of this with it.
+
+## Why there is a core at all
+
+Every Jackson data format is the same databind model behind a different factory: `XmlMapper`,
+`YAMLMapper` and `CBORMapper` are all `ObjectMapper`s. So the annotations on a type, the
+constraints its fields declare and the schema it publishes are the same whatever writes it. Only
+the mapper and the content type differ, and that is all a format module has to say.
+
+## Codec
+
+One mapper, in the shape a handler needs it.
+
+| | |
+|---|---|
+| `body(Request, Class<T>)` | Parses the body and verifies its constraints |
+| `write(Response, Object)` | Serializes and sets the format's content type |
+| `writeView(Response, Object, Class<?>)` | The same, through a Jackson `@JsonView` |
+| `mapper()` | The `ObjectMapper` itself, for everything else |
+
+`body` reads straight off the request's stream, which Flash reuses per connection: the body is
+never buffered into an array to be handed over. A malformed body is a 400, a body that breaks a
+constraint is a 422, and neither reaches the handler.
+
+## Constraints
+
+A body is checked against the `jakarta.validation` annotations its own type declares — nothing to
+install, nothing to call:
+
+```java
+public record NewUser(@NotBlank @Size(max = 80) String name, @Email String email, @Min(18) int age) {}
+```
+
+Supported: `@NotNull`, `@NotBlank`, `@NotEmpty`, `@Size`, `@Min`, `@Max`, `@Email`, `@Pattern`.
+Jakarta semantics: only `@NotNull` rejects null, every other constraint passes it.
+
+The constraints of a type are compiled the first time it is seen and kept in a `ClassValue`,
+beside the class itself — no map, no lock. A check reads the field through an exact-signature
+`MethodHandle`: no boxing, no argument array, no iterator, and nothing allocated at all unless
+something fails. A type that declares no constraints compiles to a validator that does nothing.
+
+Verify a value built by hand with `Validator.check(value)`.
+
+`flash-ext-openapi` reads the same annotations to publish `minLength`, `maximum`, `pattern` and
+the required fields, so a rule is written once and both enforced and documented.
+
+## Writing a format module
+
+```java
+public final class Yaml extends Codec {
+    public Yaml(YAMLMapper mapper) { super(mapper, ContentType.TEXT_YAML); }
+}
+
+@Consumes(ContentType.TEXT_YAML)
+public abstract class YamlHandler<B> extends JacksonHandler<B> {
+    @Inject private Yaml yaml;
+    @Override protected Codec codec() { return yaml; }
+}
+```
+
+Plus an extension that provides the codec and, for outbound bodies,
+`Marshalling.of(mapper, contentType)`. That is the whole of it.
@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-jackson-core</artifactId>
+    <name>flash-ext-jackson-core</name>
+    <description>What every Jackson data format shares: the codec, the body handler and the constraints a body is checked against.</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jsr310</artifactId>
+        </dependency>
+        <!-- The constraint annotations a body is checked against; no implementation, no transitives. -->
+        <dependency>
+            <groupId>jakarta.validation</groupId>
+            <artifactId>jakarta.validation-api</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>
@@ -1,4 +1,4 @@
-package dev.relism.flash.ext.validation;
+package dev.relism.flash.ext.jackson;

 import java.lang.invoke.MethodHandle;
 import java.util.regex.Pattern;
@@ -0,0 +1,72 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.exceptions.HttpException;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.Response;
+
+/**
+ * One Jackson mapper, in the shape a handler needs it.
+ *
+ * <p>Every Jackson data format is the same databind model behind a different factory, so this is
+ * the whole of what a format module has to say: which mapper, and which content type it writes.
+ * What the annotations mean, what a body is checked against and how a type is described are the
+ * same for all of them.
+ *
+ * <p>Retrieve it once at boot — {@code @Inject private Json json;} — and call it on the hot path.
+ * The underlying {@link ObjectMapper} is thread-safe once configured.
+ */
+public abstract class Codec {
+
+    private final ObjectMapper mapper;
+    private final ContentType contentType;
+
+    protected Codec(ObjectMapper mapper, ContentType contentType) {
+        this.mapper = mapper;
+        this.contentType = contentType;
+    }
+
+    /**
+     * Reads the request body as {@code type} and verifies its constraints.
+     *
+     * <p>Read straight off the request's stream, which Flash reuses per connection: nothing
+     * buffers the body to hand it over. A type that declares no constraints is not checked at all.
+     *
+     * @throws HttpException 400 if the body cannot be parsed as {@code type}
+     * @throws ValidationException 422 if it parses but violates a constraint
+     */
+    public <T> T body(Request request, Class<T> type) throws Exception {
+        T value;
+        try {
+            value = mapper.readValue(request.body().stream(), type);
+        } catch (JsonProcessingException malformed) {
+            throw HttpException.badRequest("Invalid request body: " + malformed.getOriginalMessage());
+        }
+        Validator.of(type).verify(value);
+        return value;
+    }
+
+    /** Serializes {@code value} and sets this codec's content type on the response. */
+    public String write(Response response, Object value) throws Exception {
+        response.type(contentType);
+        return mapper.writeValueAsString(value);
+    }
+
+    /** Like {@link #write}, restricted to the fields visible under a Jackson {@code @JsonView}. */
+    public String writeView(Response response, Object value, Class<?> view) throws Exception {
+        response.type(contentType);
+        return mapper.writerWithView(view).writeValueAsString(value);
+    }
+
+    /** What this codec writes, for a handler that sets the response type itself. */
+    public ContentType contentType() {
+        return contentType;
+    }
+
+    /** The mapper itself, for everything these methods do not cover. */
+    public ObjectMapper mapper() {
+        return mapper;
+    }
+}
@@ -0,0 +1,33 @@
+package dev.relism.flash.ext.jackson;
+
+import dev.relism.flash.models.BodyHandler;
+import dev.relism.flash.models.Request;
+
+/**
+ * A handler whose body one Jackson format parses and whose constraints are checked before it
+ * arrives.
+ *
+ * <p>Format modules extend this and name their codec — {@code JsonHandler}, {@code XmlHandler}.
+ * An application extends those, never this one.
+ *
+ * @param <B> the body type, which is also what the published OpenAPI document describes
+ */
+public abstract class JacksonHandler<B> extends BodyHandler<B> {
+
+    private final Class<B> type = bodyType();
+
+    protected JacksonHandler() {
+        if (type == null) {
+            throw new IllegalStateException(getClass().getSimpleName()
+                    + " extends a body handler without naming its body type — write it as Handler<YourBody>");
+        }
+    }
+
+    /** The format this handler speaks. Injected by the subclass, resolved once at boot. */
+    protected abstract Codec codec();
+
+    @Override
+    protected final B body(Request request) throws Exception {
+        return codec().body(request, type);
+    }
+}
@@ -0,0 +1,32 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.models.Response;
+import dev.relism.flash.routing.Middleware;
+
+/**
+ * Turns whatever a handler returns into a serialized body.
+ *
+ * <p>Pass-through for what is already a response: {@code null}, a {@link Response}, a
+ * {@code byte[]} or a {@link CharSequence}. Everything else is serialized straight to bytes.
+ */
+public final class Marshalling {
+
+    private Marshalling() {}
+
+    public static Middleware of(ObjectMapper mapper, ContentType contentType) {
+        return next -> (req, res) -> {
+            Object out = next.handle(req, res);
+            if (out == null || out instanceof Response || out instanceof byte[] || out instanceof CharSequence) return out;
+
+            res.type(contentType);
+            try {
+                return mapper.writeValueAsBytes(out);
+            } catch (JsonProcessingException failure) {
+                throw new IllegalStateException("Could not serialize " + out.getClass().getName(), failure);
+            }
+        };
+    }
+}
@@ -1,4 +1,4 @@
-package dev.relism.flash.ext.validation;
+package dev.relism.flash.ext.jackson;

 import dev.relism.flash.exceptions.HttpException;

@@ -14,7 +14,7 @@ public final class ValidationException extends HttpException {

    private final transient List<Violation> violations;

-    ValidationException(List<Violation> violations) {
+    public ValidationException(List<Violation> violations) {
        super(422, describe(violations));
        this.violations = List.copyOf(violations);
    }
@@ -1,4 +1,4 @@
-package dev.relism.flash.ext.validation;
+package dev.relism.flash.ext.jackson;

 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.Max;
@@ -31,12 +31,38 @@ public final class Validator {

    private static final Check[] NONE = new Check[0];

+    /**
+     * One compiled validator per type, kept beside the class itself: no map lookup, no lock, and
+     * the entry is collected with the class rather than pinning it.
+     */
+    private static final ClassValue<Validator> COMPILED = new ClassValue<>() {
+        @Override protected Validator computeValue(Class<?> type) {
+            return compile(type);
+        }
+    };
+
    private final Check[] checks;

    private Validator(Check[] checks) {
        this.checks = checks;
    }

+    /** The constraints of {@code type}, compiled the first time it is seen and reused after. */
+    public static Validator of(Class<?> type) {
+        return COMPILED.get(type);
+    }
+
+    /**
+     * Verifies a value against its own type's constraints.
+     *
+     * @return {@code value}, so it can be used inline
+     * @throws ValidationException 422, listing every failure
+     */
+    public static <T> T check(T value) {
+        of(value.getClass()).verify(value);
+        return value;
+    }
+
    /** True when the type declares no constraints at all — {@link #verify} is then a no-op. */
    public boolean isEmpty() {
        return checks.length == 0;
@@ -1,4 +1,4 @@
-package dev.relism.flash.ext.validation;
+package dev.relism.flash.ext.jackson;

 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.Max;
@@ -0,0 +1,60 @@
+# flash-ext-jackson-json
+
+JSON bodies and JSON responses.
+
+## Install
+
+```java
+JsonExtension json = new JsonExtension();
+
+FlashApp.create(8080)
+    .install(json)
+    .use(json.auto())
+    .scan("com.acme.handlers")
+    .startAndBlock();
+```
+
+The default mapper discovers the modules on the classpath (Java Time among them) and writes dates
+as ISO strings; `new JsonExtension(mapper)` takes one of your own. `auto()` serializes whatever a
+handler returns, leaving alone what is already a response: `null`, a `Response`, a `byte[]` or a
+`CharSequence`.
+
+## A handler with a body
+
+The body type is the handler's type argument, and that is the whole declaration — it is also what
+the OpenAPI document describes and what the constraints are read from:
+
+```java
+@POST("/users")
+public final class CreateUser extends JsonHandler<NewUser> {
+    @Inject private UserService users;
+
+    @Override protected Object handle(Request req, Response res, NewUser body) {
+        return users.create(body);
+    }
+}
+```
+
+A malformed body never reaches it (400), nor does one that breaks a constraint (422).
+
+## A handler that reads it itself
+
+```java
+public final class Import extends RequestHandler {
+    @Inject private Json json;
+
+    @Override public Object handle(Request req, Response res) throws Exception {
+        return archive.store(json.body(req, Manifest.class));
+    }
+}
+```
+
+`Json` is the [`Codec`](../flash-ext-jackson-core) for `application/json`: `body`, `write`,
+`writeView`, `mapper`.
+
+## Notes
+
+- One mapper per application (or per scope), shared by every handler; `ObjectMapper` is
+  thread-safe once configured.
+- Install `flash-ext-jackson-xml` beside this one when an application speaks both: a route picks
+  its format by the handler it extends, not by negotiation.
@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-jackson-json</artifactId>
+    <name>flash-ext-jackson-json</name>
+    <description>JSON bodies and responses: the Json codec, JsonHandler and the marshalling middleware.</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash-ext-jackson-core</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash-testing</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <!-- The constraints a body declares are described by the published document too. -->
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash-ext-openapi</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>
@@ -0,0 +1,27 @@
+package dev.relism.flash.ext.jackson.json;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.ext.jackson.Codec;
+import dev.relism.flash.http.ContentType;
+
+/**
+ * JSON in and out, checked against the body type's own constraints.
+ *
+ * <pre>{@code
+ * public final class CreateItem extends RequestHandler {
+ *     @Inject private Json json;
+ *
+ *     @Override public Object handle(Request req, Response res) throws Exception {
+ *         return items.create(json.body(req, NewItem.class));
+ *     }
+ * }
+ * }</pre>
+ *
+ * <p>A handler whose whole body is one type has nothing to write at all: see {@link JsonHandler}.
+ */
+public final class Json extends Codec {
+
+    public Json(ObjectMapper mapper) {
+        super(mapper, ContentType.JSON);
+    }
+}
@@ -0,0 +1,50 @@
+package dev.relism.flash.ext.jackson.json;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import dev.relism.flash.ext.jackson.Marshalling;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.extension.FlashExtension;
+import dev.relism.flash.extension.FlashRegistrar;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.routing.Middleware;
+
+/**
+ * JSON for an application: the {@link Json} codec, the mapper behind it, and the middleware that
+ * serializes whatever a handler returns.
+ *
+ * <pre>{@code
+ * JsonExtension json = new JsonExtension();
+ * app.install(json).use(json.auto());
+ * }</pre>
+ *
+ * <p>The default mapper discovers the modules on the classpath (Java Time among them) and writes
+ * dates as ISO strings. Hand it a mapper of your own to decide otherwise.
+ */
+public class JsonExtension implements FlashExtension {
+
+    private final ObjectMapper mapper;
+
+    public JsonExtension() {
+        this(JsonMapper.builder()
+                .findAndAddModules()
+                .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+                .build());
+    }
+
+    public JsonExtension(ObjectMapper mapper) {
+        this.mapper = mapper;
+    }
+
+    /** Serializes what a handler returns, unless it already returned a response, bytes or text. */
+    public Middleware auto() {
+        return Marshalling.of(mapper, ContentType.JSON);
+    }
+
+    @Override
+    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
+        ctx.provide(Json.class, new Json(mapper));
+        ctx.provide(ObjectMapper.class, mapper);
+    }
+}
@@ -0,0 +1,35 @@
+package dev.relism.flash.ext.jackson.json;
+
+import dev.relism.flash.ext.jackson.Codec;
+import dev.relism.flash.ext.jackson.JacksonHandler;
+import dev.relism.flash.extension.Inject;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.routing.Consumes;
+
+/**
+ * A handler that takes a JSON body of one type.
+ *
+ * <pre>{@code
+ * @POST("/users")
+ * public final class CreateUser extends JsonHandler<NewUser> {
+ *     @Inject private UserService users;
+ *
+ *     @Override protected Object handle(Request req, Response res, NewUser body) {
+ *         return users.create(body);
+ *     }
+ * }
+ * }</pre>
+ *
+ * <p>The body is read off the request stream, verified against the constraints its type declares,
+ * and handed over. A malformed body is a 400, a body that breaks a constraint is a 422, and
+ * neither ever reaches the handler. The published OpenAPI document describes the same type.
+ */
+@Consumes(ContentType.JSON)
+public abstract class JsonHandler<B> extends JacksonHandler<B> {
+
+    @Inject private Json json;
+
+    @Override protected final Codec codec() {
+        return json;
+    }
+}
@@ -1,6 +1,6 @@
-package dev.relism.flash.ext.validation;
+package dev.relism.flash.ext.jackson.json;

-import dev.relism.flash.ext.jackson.JacksonExtension;
+import dev.relism.flash.ext.jackson.json.JsonExtension;
 import dev.relism.flash.ext.openapi.APIResponse;
 import dev.relism.flash.ext.openapi.ApiOperation;
 import dev.relism.flash.ext.openapi.Content;
@@ -24,7 +24,7 @@ import org.junit.jupiter.api.extension.RegisterExtension;
 * describes them. Nothing registers this bridge — flash-ext-openapi picks the annotations up on
 * its own when they are on the classpath.
 */
-class ValidationOpenApiInteropTest {
+class ConstraintsInTheDocumentTest {

    record Account(
            @NotBlank @Size(max = 40) String name,
@@ -42,10 +42,9 @@ class ValidationOpenApiInteropTest {

    @RegisterExtension
    static FlashTest app = FlashTest.of(configured -> {
-        configured.install(new JacksonExtension());
-        configured.install(new ValidationExtension());
-        configured.install(new OpenApiExtension("/openapi", "Accounts", "1.0.0"));
-        configured.scan("dev.relism.flash.ext.validation");
+        configured.install(new JsonExtension());
+                configured.install(new OpenApiExtension("/openapi", "Accounts", "1.0.0"));
+        configured.scan("dev.relism.flash.ext.jackson.json");
    });

    @Test
@@ -1,4 +1,4 @@
-package dev.relism.flash.ext.jackson;
+package dev.relism.flash.ext.jackson.json;

 import com.fasterxml.jackson.databind.ObjectMapper;
 import dev.relism.flash.extension.FlashContext;
@@ -16,26 +16,25 @@ import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertTrue;

-class JacksonExtensionTest {
+class JsonExtensionTest {

    @Test
    void configure_registers_json_mapper_and_middleware() {
        FlashContext ctx = new FlashContext();
        ObjectMapper mapper = new ObjectMapper();
-        JacksonExtension ext = new JacksonExtension(mapper);
+        JsonExtension ext = new JsonExtension(mapper);

        ext.configure(null, ctx);
        ctx.complete();

        assertNotNull(ctx.require(Json.class));
-        assertNotNull(ctx.require(JacksonMiddleware.class));
        assertSame(mapper, ctx.require(ObjectMapper.class));
    }

    @Test
-    void autoJson_factory_delegates_to_middleware_policy() throws Exception {
+    void auto_marshals_what_a_handler_returns() throws Exception {
        ObjectMapper mapper = new ObjectMapper();
-        JacksonExtension ext = new JacksonExtension(mapper);
+        JsonExtension ext = new JsonExtension(mapper);
        RequestHandler next = new RequestHandler() {
            @Override
            public Object handle(Request request, Response response) {
@@ -43,7 +42,7 @@ class JacksonExtensionTest {
            }
        };
        RequestHandler wrapped = new RequestHandler() {
-            private final SimpleHandler.FunctionalHandler delegate = ext.autoJson().wrap(next);
+            private final SimpleHandler.FunctionalHandler delegate = ext.auto().wrap(next);

            @Override
            public Object handle(Request request, Response response) throws Exception {
@@ -0,0 +1,78 @@
+package dev.relism.flash.ext.jackson.json;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.http.HttpMethod;
+import dev.relism.flash.models.Http1HeaderMap;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.RequestLine;
+import dev.relism.flash.models.Response;
+import dev.relism.flash.routing.routers.fastpathrouter.FastPathViews;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class JsonHandlerTest {
+
+    public record NewUser(String name) {}
+
+    static final class Create extends JsonHandler<NewUser> {
+        @Override protected Object handle(Request request, Response response, NewUser body) {
+            return body.name();
+        }
+    }
+
+    @SuppressWarnings("rawtypes")
+    static final class Untyped extends JsonHandler {
+        @Override protected Object handle(Request request, Response response, Object body) {
+            return null;
+        }
+    }
+
+    @Test
+    void theBodyArrivesParsedAsTheTypeTheHandlerDeclares() throws Exception {
+        Create handler = new Create();
+        handler.bind(context());
+
+        Object answer = handler.handle(request("{\"name\":\"alice\"}"), new Response(200, ContentType.JSON));
+
+        assertEquals("alice", answer);
+    }
+
+    @Test
+    void aMalformedBodyIsTheUsualBadRequest() throws Exception {
+        Create handler = new Create();
+        handler.bind(context());
+
+        dev.relism.flash.exceptions.HttpException refused = assertThrows(dev.relism.flash.exceptions.HttpException.class,
+                () -> handler.handle(request("not json"), new Response(200, ContentType.JSON)));
+
+        assertEquals(400, refused.status());
+    }
+
+    @Test
+    void aHandlerThatNeverNamedItsBodyTypeIsRefusedAtBoot() {
+        IllegalStateException refused = assertThrows(IllegalStateException.class, Untyped::new);
+
+        assertTrue(refused.getMessage().contains("Handler<YourBody>"), refused.getMessage());
+    }
+
+    private static FlashContext context() {
+        FlashContext ctx = new FlashContext();
+        ctx.provide(Json.class, new Json(new ObjectMapper()));
+        ctx.complete();
+        return ctx;
+    }
+
+    private static Request request(String body) {
+        return new Request(new RequestLine(HttpMethod.POST,
+                new FastPathViews.StringByteView("/users"), null,
+                new FastPathViews.StringByteView("HTTP/1.1"), new Http1HeaderMap()),
+                body.getBytes(StandardCharsets.UTF_8));
+    }
+}
@@ -1,4 +1,4 @@
-package dev.relism.flash.ext.jackson;
+package dev.relism.flash.ext.jackson.json;

 import com.fasterxml.jackson.annotation.JsonView;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -37,16 +37,11 @@ class JsonTest {
    }

    @Test
-    void bodyFrom_parses_stream_and_maps_bad_payload_to_http_400() throws Exception {
+    void a_truncated_body_is_a_bad_request_too() throws Exception {
        Json json = new Json(new ObjectMapper());

-        Request ok = request("{\"id\":\"u2\",\"name\":\"bob\"}");
-        UserDto dto = json.bodyFrom(ok, UserDto.class);
-        assertEquals("u2", dto.id);
-        assertEquals("bob", dto.name);
+        HttpException ex = assertThrows(HttpException.class, () -> json.body(request("["), UserDto.class));

-        Request bad = request("[");
-        HttpException ex = assertThrows(HttpException.class, () -> json.bodyFrom(bad, UserDto.class));
        assertEquals(400, ex.status());
    }

@@ -1,6 +1,8 @@
-package dev.relism.flash.ext.jackson;
+package dev.relism.flash.ext.jackson.json;

 import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.ext.jackson.Marshalling;
+import dev.relism.flash.routing.Middleware;
 import dev.relism.flash.models.SimpleHandler;
 import dev.relism.flash.http.ContentType;
 import dev.relism.flash.models.Request;
@@ -16,13 +18,13 @@ import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;

-class JacksonMiddlewareTest {
+class MarshallingTest {

    private static final Request REQ = null;

    @Test
-    void autoJson_marshalsPojo_toJsonBytes_and_setsJsonContentType() throws Exception {
-        JacksonMiddleware mw = new JacksonMiddleware(new ObjectMapper());
+    void marshalling_marshalsPojo_toJsonBytes_and_setsJsonContentType() throws Exception {
+        Middleware mw = Marshalling.of(new ObjectMapper(), ContentType.JSON);
        RequestHandler wrapped = wrap(mw, new UserDto("u1", "alice"));
        Response res = new Response(200, ContentType.TEXT_PLAIN);

@@ -34,8 +36,8 @@ class JacksonMiddlewareTest {
    }

    @Test
-    void autoJson_passThrough_for_response_string_charSequence_bytes_and_null() throws Exception {
-        JacksonMiddleware mw = new JacksonMiddleware(new ObjectMapper());
+    void marshalling_passThrough_for_response_string_charSequence_bytes_and_null() throws Exception {
+        Middleware mw = Marshalling.of(new ObjectMapper(), ContentType.JSON);

        Response payloadResponse = new Response(201, ContentType.TEXT_PLAIN).body("ok");
        RequestHandler wrappedResponse = wrap(mw, payloadResponse);
@@ -55,17 +57,17 @@ class JacksonMiddlewareTest {
    }

    @Test
-    void autoJson_wraps_serialization_errors_as_illegal_state() {
-        JacksonMiddleware mw = new JacksonMiddleware(new ObjectMapper());
+    void marshalling_wraps_serialization_errors_as_illegal_state() {
+        Middleware mw = Marshalling.of(new ObjectMapper(), ContentType.JSON);
        RequestHandler wrapped = wrap(mw, new CyclicDto());
        Response res = new Response(200, ContentType.TEXT_PLAIN);

        IllegalStateException ex = assertThrows(IllegalStateException.class, () -> wrapped.handle(REQ, res));
        assertEquals("application/json", new String(res.getContentType(), StandardCharsets.UTF_8));
-        assertTrue(ex.getMessage().startsWith("Failed to serialize handler result as JSON:"));
+        assertTrue(ex.getMessage().startsWith("Could not serialize"));
    }

-    private static RequestHandler wrap(JacksonMiddleware mw, Object fixedReturn) {
+    private static RequestHandler wrap(Middleware mw, Object fixedReturn) {
        RequestHandler next = new RequestHandler() {
            @Override
            public Object handle(Request request, Response response) {
@@ -73,7 +75,7 @@ class JacksonMiddlewareTest {
            }
        };
        return new RequestHandler() {
-            private final SimpleHandler.FunctionalHandler delegate = mw.autoJson().wrap(next);
+            private final SimpleHandler.FunctionalHandler delegate = mw.wrap(next);

            @Override
            public Object handle(Request request, Response response) throws Exception {
@@ -1,6 +1,5 @@
-package dev.relism.flash.ext.validation;
+package dev.relism.flash.ext.jackson.json;

-import dev.relism.flash.ext.jackson.JacksonExtension;
 import dev.relism.flash.testing.FlashTest;
 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.Min;
@@ -12,19 +11,18 @@ import org.junit.jupiter.api.extension.RegisterExtension;
 import static org.junit.jupiter.api.Assertions.assertEquals;

 /** The whole path: JSON in, constraints checked, status out — with no error handling wired up. */
-class ValidationRoutesTest {
+class ValidatedBodyTest {

    record CreateUser(@NotBlank @Size(max = 8) String name, @Email String email, @Min(18) int age) {}

    @RegisterExtension
    static FlashTest app = FlashTest.of(configured -> {
-        configured.install(new JacksonExtension());
-        configured.install(new ValidationExtension());
+        configured.install(new JsonExtension());

        configured.ctx().onReady(() -> {
-            Validation validation = configured.ctx().require(Validation.class);
+            Json json = configured.ctx().require(Json.class);
            configured.post("/users", (req, res) ->
-                    res.status(201).body("created:" + validation.body(req, CreateUser.class).name()));
+                    res.status(201).body("created:" + json.body(req, CreateUser.class).name()));
        });
    });

@@ -0,0 +1,30 @@
+# flash-ext-jackson-xml
+
+XML bodies and XML responses, over the same types as every other Jackson format.
+
+```java
+XmlExtension xml = new XmlExtension();
+app.install(xml).use(xml.auto());
+```
+
+```java
+@POST("/orders")
+public final class PlaceOrder extends XmlHandler<Order> {
+    @Inject private OrderService orders;
+
+    @Override protected Object handle(Request req, Response res, Order body) {
+        return orders.place(body);
+    }
+}
+```
+
+Everything [`flash-ext-jackson-json`](../flash-ext-jackson-json) does, in XML: the body is read off
+the request stream, verified against the constraints its type declares, and handed over. A type
+annotated for JSON works here as is — `Order` can be a JSON body on one route and an XML body on
+another.
+
+What is specific to XML is Jackson's own: `@JacksonXmlRootElement` for the root name,
+`@JacksonXmlProperty(isAttribute = true)` for an attribute rather than an element, and
+`@JacksonXmlElementWrapper` for how a list is wrapped. This module adds no annotations of its own.
+
+Brings `jackson-dataformat-xml`, and with it Woodstox.
@@ -10,42 +10,34 @@
        <version>2.1.0-SNAPSHOT</version>
    </parent>

-    <artifactId>flash-ext-validation</artifactId>
+    <artifactId>flash-ext-jackson-xml</artifactId>
+    <name>flash-ext-jackson-xml</name>
+    <description>XML bodies and responses, over the same types and the same constraints as every other Jackson format.</description>

    <dependencies>
        <dependency>
            <groupId>dev.relism</groupId>
-            <artifactId>flash</artifactId>
+            <artifactId>flash-ext-jackson-core</artifactId>
        </dependency>
-        <!--
-          Annotations only (~90 KB). Hibernate Validator's engine is deliberately absent: it
-          resolves constraints reflectively per call and pulls ~2 MB plus EL. This module
-          compiles the same annotations into a flat check table once per class instead.
-        -->
        <dependency>
-            <groupId>jakarta.validation</groupId>
-            <artifactId>jakarta.validation-api</artifactId>
-        </dependency>
-        <!-- Only needed for Validation.body(...); check(...) works without it. -->
-        <dependency>
-            <groupId>dev.relism</groupId>
-            <artifactId>flash-ext-jackson</artifactId>
-            <optional>true</optional>
+            <groupId>com.fasterxml.jackson.dataformat</groupId>
+            <artifactId>jackson-dataformat-xml</artifactId>
        </dependency>
+
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.validation</groupId>
+            <artifactId>jakarta.validation-api</artifactId>
+            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>dev.relism</groupId>
            <artifactId>flash-testing</artifactId>
            <scope>test</scope>
        </dependency>
-        <!-- Interop only: proves constraints reach the published schema. -->
-        <dependency>
-            <groupId>dev.relism</groupId>
-            <artifactId>flash-ext-openapi</artifactId>
-            <scope>test</scope>
-        </dependency>
    </dependencies>
 </project>
@@ -0,0 +1,20 @@
+package dev.relism.flash.ext.jackson.xml;
+
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import dev.relism.flash.ext.jackson.Codec;
+import dev.relism.flash.http.ContentType;
+
+/**
+ * XML in and out, checked against the body type's own constraints.
+ *
+ * <p>The same databind model as every other Jackson format: a type is annotated once and can be
+ * read as XML here and as JSON elsewhere in the same application. XML's own concerns — a root
+ * element name, an attribute rather than an element, how a list is wrapped — are Jackson's
+ * {@code @JacksonXml*} annotations on the type.
+ */
+public final class Xml extends Codec {
+
+    public Xml(XmlMapper mapper) {
+        super(mapper, ContentType.XML);
+    }
+}
@@ -0,0 +1,44 @@
+package dev.relism.flash.ext.jackson.xml;
+
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import dev.relism.flash.ext.jackson.Marshalling;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.extension.FlashExtension;
+import dev.relism.flash.extension.FlashRegistrar;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.routing.Middleware;
+
+/**
+ * XML for an application: the {@link Xml} codec and the middleware that serializes what a handler
+ * returns.
+ *
+ * <pre>{@code
+ * XmlExtension xml = new XmlExtension();
+ * app.install(xml).use(xml.auto());
+ * }</pre>
+ *
+ * <p>Install it beside {@code JsonExtension} when an application speaks both: each provides its
+ * own codec, and a route picks one by the handler it extends.
+ */
+public class XmlExtension implements FlashExtension {
+
+    private final XmlMapper mapper;
+
+    public XmlExtension() {
+        this(XmlMapper.builder().findAndAddModules().build());
+    }
+
+    public XmlExtension(XmlMapper mapper) {
+        this.mapper = mapper;
+    }
+
+    /** Serializes what a handler returns, unless it already returned a response, bytes or text. */
+    public Middleware auto() {
+        return Marshalling.of(mapper, ContentType.XML);
+    }
+
+    @Override
+    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
+        ctx.provide(Xml.class, new Xml(mapper));
+    }
+}
@@ -0,0 +1,24 @@
+package dev.relism.flash.ext.jackson.xml;
+
+import dev.relism.flash.ext.jackson.Codec;
+import dev.relism.flash.ext.jackson.JacksonHandler;
+import dev.relism.flash.extension.Inject;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.routing.Consumes;
+
+/**
+ * A handler that takes an XML body of one type.
+ *
+ * <p>Everything {@code JsonHandler} does, in XML: the body is read off the request stream,
+ * verified against its type's constraints, and handed over. Both can live in the same
+ * application, on different routes, over the same types.
+ */
+@Consumes(ContentType.XML)
+public abstract class XmlHandler<B> extends JacksonHandler<B> {
+
+    @Inject private Xml xml;
+
+    @Override protected final Codec codec() {
+        return xml;
+    }
+}
@@ -0,0 +1,81 @@
+package dev.relism.flash.ext.jackson.xml;
+
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import dev.relism.flash.exceptions.HttpException;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.http.HttpMethod;
+import dev.relism.flash.models.Http1HeaderMap;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.RequestLine;
+import dev.relism.flash.models.Response;
+import dev.relism.flash.routing.routers.fastpathrouter.FastPathViews;
+import jakarta.validation.constraints.NotBlank;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+/** The same handler shape as JSON, over the same types and the same constraints. */
+class XmlHandlerTest {
+
+    public record Order(@NotBlank String reference) {}
+
+    static final class Place extends XmlHandler<Order> {
+        @Override protected Object handle(Request request, Response response, Order body) {
+            return body.reference();
+        }
+    }
+
+    @Test
+    void theBodyArrivesParsedAsTheTypeTheHandlerDeclares() throws Exception {
+        Place handler = new Place();
+        handler.bind(context());
+
+        Object answer = handler.handle(request("<Order><reference>A-1</reference></Order>"), response());
+
+        assertEquals("A-1", answer);
+    }
+
+    @Test
+    void aBodyThatBreaksAConstraintNeverReachesTheHandler() throws Exception {
+        Place handler = new Place();
+        handler.bind(context());
+
+        HttpException refused = assertThrows(HttpException.class,
+                () -> handler.handle(request("<Order><reference></reference></Order>"), response()));
+
+        assertEquals(422, refused.status());
+    }
+
+    @Test
+    void aMalformedBodyIsABadRequest() throws Exception {
+        Place handler = new Place();
+        handler.bind(context());
+
+        HttpException refused = assertThrows(HttpException.class,
+                () -> handler.handle(request("<Order><reference>"), response()));
+
+        assertEquals(400, refused.status());
+    }
+
+    private static FlashContext context() {
+        FlashContext ctx = new FlashContext();
+        ctx.provide(Xml.class, new Xml(XmlMapper.builder().build()));
+        ctx.complete();
+        return ctx;
+    }
+
+    private static Response response() {
+        return new Response(200, ContentType.XML);
+    }
+
+    private static Request request(String body) {
+        return new Request(new RequestLine(HttpMethod.POST,
+                new FastPathViews.StringByteView("/orders"), null,
+                new FastPathViews.StringByteView("HTTP/1.1"), new Http1HeaderMap()),
+                body.getBytes(StandardCharsets.UTF_8));
+    }
+}
@@ -1,116 +0,0 @@
-# flash-ext-jackson
-
-Jackson JSON integration for Flash with an opinionated auto-marshal middleware.
-
-## What it provides
-
-| Component | Description |
-|---|---|
-| `JacksonExtension` | Registers JSON services into `FlashContext` |
-| `Json` | JSON read/write helper (`body`, `bodyFrom`, `write`, `writeView`) |
-| `ObjectMapper` | Raw mapper escape hatch for advanced usage |
-| `JacksonMiddleware` | `autoJson()` middleware for automatic outbound JSON marshalling |
-
-Default mapper behavior (`new JacksonExtension()`):
-
- auto-discovers Jackson modules on classpath (`findAndAddModules()`)
- includes Java Time support (`jackson-datatype-jsr310`)
- writes date/time values as ISO-8601 strings (not numeric timestamps)
-
-## Recommended default
-
-Install the extension, then apply `autoJson()` once at app or scope level.
-
-```java
-JacksonExtension jackson = new JacksonExtension();
-
-FlashApp app = FlashApp.create(8080)
-    .install(jackson)
-    .use(jackson.autoJson());
-
-app.startAndBlock();
-```
-
-Behavior of `autoJson()`:
-
- pass-through: `null`, `Response`, `byte[]`, `String`, `CharSequence`
- any other return value: serialize to JSON `byte[]`
- sets `Content-Type: application/json` for marshalled responses
- serialization failures throw `IllegalStateException`
-
-This keeps handlers concise while preserving Flash's direct byte write path.
-
-## Installation
-
-```xml
-<dependency>
-    <groupId>dev.relism</groupId>
-    <artifactId>flash-ext-jackson</artifactId>
-    <version>1.1-indev2</version>
-</dependency>
-```
-
-## Json helper API
-
-Use `Json` when you want explicit, local control in a handler.
-
-```java
-@POST("/users")
-public final class CreateUser extends RequestHandler {
-    private Json json;
-
-    @Override
-    protected void onInit() {
-        json = require(Json.class);
-    }
-
-    @Override
-    public Object handle(Request req, Response res) throws Exception {
-        CreateUserBody body = json.body(req, CreateUserBody.class);
-        UserDto created = service.create(body);
-        res.status(201);
-        return json.write(res, created);
-    }
-}
-```
-
-Methods:
-
- `body(req, Type.class)` -> parse from `req.body().bytes()`
- `bodyFrom(req, Type.class)` -> parse from `req.body().stream()`
- `write(res, obj)` -> writes JSON string and sets JSON content type
- `writeView(res, obj, View.class)` -> JSON with Jackson `@JsonView`
- `mapper()` -> raw `ObjectMapper`
-
-## Custom mapper
-
-```java
-ObjectMapper mapper = JsonMapper.builder()
-    .addModule(new JavaTimeModule())
-    .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
-    .build();
-
-FlashApp.create(8080)
-    .install(new JacksonExtension(mapper));
-```
-
-## Scope usage
-
-`autoJson()` works the same at scope level:
-
-```java
-JacksonExtension jackson = new JacksonExtension();
-
-app.mount("/api", api -> {
-    api.use(jackson.autoJson());
-    api.get("/health", (req, res) -> Map.of("ok", true));
-});
-```
-
-If you need to pull it from context, `JacksonMiddleware` is also provided as a service
-after the app boots (same lifecycle model as other extension-provided services).
-
-## Notes
-
- Install order is irrelevant (Flash two-phase extension lifecycle).
- `autoJson()` and OpenAPI are intentionally decoupled.
@@ -1,82 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-
-    <parent>
-        <groupId>dev.relism</groupId>
-        <artifactId>flash-extensions</artifactId>
-        <version>2.1.0-SNAPSHOT</version>
-    </parent>
-
-    <artifactId>flash-ext-jackson</artifactId>
-
-    <properties>
-        <jacoco.version>0.8.12</jacoco.version>
-    </properties>
-
-    <dependencies>
-        <dependency>
-            <groupId>dev.relism</groupId>
-            <artifactId>flash</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>com.fasterxml.jackson.core</groupId>
-            <artifactId>jackson-databind</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>com.fasterxml.jackson.datatype</groupId>
-            <artifactId>jackson-datatype-jsr310</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter</artifactId>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.jacoco</groupId>
-                <artifactId>jacoco-maven-plugin</artifactId>
-                <version>${jacoco.version}</version>
-                <executions>
-                    <execution>
-                        <id>jacoco-prepare-agent</id>
-                        <goals>
-                            <goal>prepare-agent</goal>
-                        </goals>
-                    </execution>
-                    <execution>
-                        <id>jacoco-report-and-check</id>
-                        <phase>verify</phase>
-                        <goals>
-                            <goal>report</goal>
-                            <goal>check</goal>
-                        </goals>
-                        <configuration>
-                            <rules>
-                                <rule>
-                                    <element>BUNDLE</element>
-                                    <limits>
-                                        <limit>
-                                            <counter>LINE</counter>
-                                            <value>COVEREDRATIO</value>
-                                            <minimum>0.80</minimum>
-                                        </limit>
-                                    </limits>
-                                </rule>
-                            </rules>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-        </plugins>
-    </build>
-
-</project>
@@ -1,94 +0,0 @@
-package dev.relism.flash.ext.jackson;
-
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.databind.SerializationFeature;
-import com.fasterxml.jackson.databind.json.JsonMapper;
-import dev.relism.flash.extension.FlashContext;
-import dev.relism.flash.extension.FlashRegistrar;
-import dev.relism.flash.extension.FlashExtension;
-import dev.relism.flash.routing.Middleware;
-
-/**
- * Registers JSON support into the Flash extension layer.
- *
- * <p>Exposes a {@link Json} utility instance in the {@link FlashContext} under
- * {@code Json.class}. Any handler or extension can retrieve it via {@code ctx.require(Json.class)}
- * inside {@code onInit()} (class-based) or from a {@link FlashContext#onReady(Runnable)}
- * callback (extensions).
- *
- * <p>The raw {@link ObjectMapper} is also registered under {@code ObjectMapper.class}
- * for extensions that need direct mapper access (e.g. OpenAPI schema generation).
- *
- * <p>{@link JacksonMiddleware} is provided under {@code JacksonMiddleware.class} and
- * exposes opinionated JSON auto-marshalling middleware via {@link JacksonMiddleware#autoJson()}.
- *
- * <h3>Usage — composition (preferred)</h3>
- * <pre>{@code
- * public class MyHandler extends RequestHandler {
- *     private Json json;
- *
- *     @Override protected void onInit() {
- *         json = require(Json.class);
- *     }
- *
- *     public Object handle(Request req, Response res) throws Exception {
- *         MyDto dto = json.body(req, MyDto.class);
- *         return json.write(res, 201, dto);
- *     }
- * }
- * }</pre>
- *
- * <h3>Custom mapper</h3>
- * <pre>{@code
- * ObjectMapper mapper = JsonMapper.builder()
- *         .addModule(new JavaTimeModule())
- *         .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
- *         .build();
- *
- * FlashApp.create(8080)
- *         .install(new JacksonExtension(mapper));
- * }</pre>
- */
-public class JacksonExtension implements FlashExtension {
-
-    private final ObjectMapper mapper;
-    private final JacksonMiddleware middleware;
-
-    /**
-     * Installs with an opinionated default {@link JsonMapper}:
-     * auto-discovers modules on classpath (e.g. Java Time) and writes dates as ISO strings.
-     */
-    public JacksonExtension() {
-        this(JsonMapper.builder()
-                .findAndAddModules()
-                .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
-                .build());
-    }
-
-    /** Installs with a fully configured custom {@link ObjectMapper}. */
-    public JacksonExtension(ObjectMapper mapper) {
-        this.mapper = mapper;
-        this.middleware = new JacksonMiddleware(mapper);
-    }
-
-    /**
-     * Opinionated outbound JSON middleware factory.
-     *
-     * <p>Use for app/scope-level registration:
-     * <pre>{@code
-     * JacksonExtension jackson = new JacksonExtension();
-     * app.install(jackson).use(jackson.autoJson());
-     * }</pre>
-     */
-    public Middleware autoJson() {
-        return middleware.autoJson();
-    }
-
-    @Override
-    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
-        Json json = new Json(mapper);
-        ctx.provide(Json.class,               json);
-        ctx.provide(ObjectMapper.class,       mapper);
-        ctx.provide(JacksonMiddleware.class,  middleware);
-    }
-}
@@ -1,62 +0,0 @@
-package dev.relism.flash.ext.jackson;
-
-import com.fasterxml.jackson.core.JsonProcessingException;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import dev.relism.flash.http.ContentType;
-import dev.relism.flash.models.Response;
-import dev.relism.flash.routing.Middleware;
-
-/**
- * Outbound JSON marshalling middleware for class-based and lambda routes.
- *
- * <p>{@link #autoJson()} marshals any non-body-native return value to JSON bytes,
- * writes {@code Content-Type: application/json}, and returns {@code byte[]} so
- * the Flash write path stays direct.
- *
- * <p>Pass-through return types:
- * <ul>
- *   <li>{@code null}</li>
- *   <li>{@link Response}</li>
- *   <li>{@code byte[]}</li>
- *   <li>{@link String}</li>
- *   <li>{@link CharSequence}</li>
- * </ul>
- */
-public final class JacksonMiddleware {
-
-    private final ObjectMapper mapper;
-
-    JacksonMiddleware(ObjectMapper mapper) {
-        this.mapper = mapper;
-    }
-
-    /**
-     * Automatic JSON marshalling policy.
-     *
-     * <p>For non-pass-through return values, serializes with Jackson directly to
-     * {@code byte[]} and sets response content type to JSON.
-     *
-     * @throws IllegalStateException when serialization fails
-     */
-    public Middleware autoJson() {
-        return next -> (req, res) -> {
-            Object out = next.handle(req, res);
-            if (isPassThrough(out)) return out;
-
-            res.type(ContentType.JSON);
-            try {
-                return mapper.writeValueAsBytes(out);
-            } catch (JsonProcessingException e) {
-                throw new IllegalStateException(
-                        "Failed to serialize handler result as JSON: " + out.getClass().getName(), e);
-            }
-        };
-    }
-
-    private static boolean isPassThrough(Object out) {
-        return out == null
-                || out instanceof Response
-                || out instanceof byte[]
-                || out instanceof CharSequence;
-    }
-}
@@ -1,117 +0,0 @@
-package dev.relism.flash.ext.jackson;
-
-import com.fasterxml.jackson.core.JsonProcessingException;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import dev.relism.flash.exceptions.HttpException;
-import dev.relism.flash.http.ContentType;
-import dev.relism.flash.models.Request;
-import dev.relism.flash.models.Response;
-
-/**
- * Thread-safe JSON toolbox. Single point of access for all JSON I/O operations
- * within a Flash application.
- *
- * <p>Retrieve once at boot time via {@code require(Json.class)} inside
- * {@code onInit()}, cache in a private field, and call on the hot path
- * with zero lookup or allocation overhead:
- *
- * <pre>{@code
- * @Route(method = HttpMethod.POST, path = "/api/items")
- * public class CreateItemHandler extends RequestHandler {
- *
- *     private Json json;
- *
- *     @Override
- *     protected void onInit() {
- *         json = require(Json.class);
- *     }
- *
- *     public Object handle(Request req, Response res) throws Exception {
- *         CreateItemRequest body = json.body(req, CreateItemRequest.class);
- *         return json.write(res, itemService.create(body));
- *     }
- * }
- * }</pre>
- *
- * <p>The underlying {@link ObjectMapper} is shared across all handlers in the same
- * scope (one instance per app / per child scope). Jackson's {@code ObjectMapper}
- * is fully thread-safe after configuration — no synchronization is needed.
- *
- * <p>Install via {@link JacksonExtension} before calling {@code scan()} or
- * {@code register()}.
- */
-public final class Json {
-
-    private final ObjectMapper mapper;
-
-    /** Package-private — constructed exclusively by {@link JacksonExtension}. */
-    Json(ObjectMapper mapper) {
-        this.mapper = mapper;
-    }
-
-    // ── Input ─────────────────────────────────────────────────────────────────
-
-    /**
-     * Deserializes the full request body into an instance of {@code type}.
-     *
-     * <p>Reads {@code req.body().bytes()} in one shot. For streaming bodies
-     * use {@link #bodyFrom(Request, Class)} instead.
-     *
-     * @throws HttpException 400 if the body cannot be parsed as {@code type}
-     */
-    public <T> T body(Request req, Class<T> type) throws Exception {
-        try {
-            return mapper.readValue(req.body().bytes(), type);
-        } catch (JsonProcessingException e) {
-            throw HttpException.badRequest("Invalid request body: " + e.getOriginalMessage());
-        }
-    }
-
-    /**
-     * Deserializes the request body via the raw {@link java.io.InputStream},
-     * avoiding the intermediate {@code byte[]} allocation. Prefer this for
-     * large bodies or when allocation budget is tight.
-     *
-     * @throws HttpException 400 on parse failure
-     */
-    public <T> T bodyFrom(Request req, Class<T> type) throws Exception {
-        try {
-            return mapper.readValue(req.body().stream(), type);
-        } catch (JsonProcessingException e) {
-            throw HttpException.badRequest("Invalid request body: " + e.getOriginalMessage());
-        }
-    }
-
-    // ── Output ────────────────────────────────────────────────────────────────
-
-    /**
-     * Serializes {@code obj} to a JSON string and sets
-     * {@code Content-Type: application/json} on the response.
-     *
-     * <p>The returned string is used as the response body by the Flash runtime.
-     */
-    public String write(Response res, Object obj) throws Exception {
-        res.type(ContentType.JSON);
-        return mapper.writeValueAsString(obj);
-    }
-
-    /**
-     * Like {@link #write} but applies a Jackson {@code @JsonView} filter,
-     * restricting serialization to fields visible under {@code view}.
-     */
-    public String writeView(Response res, Object obj, Class<?> view) throws Exception {
-        res.type(ContentType.JSON);
-        return mapper.writerWithView(view).writeValueAsString(obj);
-    }
-
-    // ── Escape hatch ──────────────────────────────────────────────────────────
-
-    /**
-     * Returns the underlying {@link ObjectMapper} for advanced operations
-     * (custom serialization, schema generation, etc.) not covered by the
-     * methods above.
-     */
-    public ObjectMapper mapper() {
-        return mapper;
-    }
-}
@@ -1,143 +0,0 @@
-# flash-ext-validation
-
-Request validation for Flash. Standard `jakarta.validation` annotations, compiled once per type
-into a flat check table, with zero allocation on the passing path.
-
-## What it provides
-
-| Component | Description |
-|---|---|
-| `Validation` | The service — `body(req, type)` parses and verifies, `validate(value)` verifies |
-| `Validator` | One type's compiled constraints; reusable and thread-safe |
-| `ValidationException` | 422 carrying every violation, not just the first |
-
-## Dependency
-
-```xml
-<dependency>
-    <groupId>dev.relism</groupId>
-    <artifactId>flash-ext-validation</artifactId>
-    <version>${flash.version}</version>
-</dependency>
-```
-
-## Quick start
-
-```java
-FlashApp.create(8080)
-    .install(new JacksonExtension())
-    .install(new ValidationExtension())
-    .scan("dev.example.api");
-```
-
-```java
-public record CreateUser(
-        @NotBlank @Size(max = 80) String name,
-        @Email                    String email,
-        @Min(18)                  int    age) {}
-```
-
-```java
-@POST("/api/users")
-public final class CreateUserHandler extends RequestHandler {
-
-    private Validation validation;
-    private UserService users;
-
-    @Override protected void onInit() {
-        validation = require(Validation.class);
-        users      = require(UserService.class);
-    }
-
-    @Override public Object handle(Request req, Response res) throws Exception {
-        CreateUser dto = validation.body(req, CreateUser.class);
-        return res.status(201).body(users.create(dto));
-    }
-}
-```
-
-There is nothing to configure. Constraints come from the annotations already on your types, and
-failures reach the client as `422` on their own — see [Error responses](#error-responses).
-
-## Supported constraints
-
-`@NotNull` · `@NotBlank` · `@NotEmpty` · `@Size` · `@Min` · `@Max` · `@Email` · `@Pattern`
-
-Jakarta null semantics are honoured exactly: **only `@NotNull` rejects null**. Every other
-constraint passes a null value, so `@Email String email` means "if present, must look like an
-email" — combine with `@NotNull` when it is mandatory.
-
-`@Size` applies to `CharSequence`, `Collection`, `Map` and object arrays. `@Min`/`@Max` apply to
-primitive integrals and to `Number` subtypes.
-
-An unsupported annotation is ignored rather than rejected, so adding one is never a boot failure.
-
-## Records and classes
-
-Constraints are read from **declared fields**. A constraint on a record component propagates to
-its backing field, so records and plain classes take the same path with no extra configuration:
-
-```java
-record CreateUser(@NotBlank String name) {}          // works
-class  CreateUser { @NotBlank private String name; } // works
-```
-
-## Error responses
-
-`ValidationException` extends Flash's `HttpException` with status 422, so the default exception
-handler renders it. Nothing is registered, and your own `onException` still wins if you set one.
-
-```json
-{"error":"name must not be blank; age must be at least 18","status":422}
-```
-
-Malformed JSON is a different failure and comes back as `400` from the codec, before any
-constraint runs.
-
-## OpenAPI
-
-Install `flash-ext-openapi` alongside and the generated schema mirrors the same annotations —
-`minLength`, `maxLength`, `minItems`, `minimum`, `maximum`, `pattern`, `format: email`, and
-`required`. Declared once, enforced and published.
-
-Nothing registers this. `flash-ext-openapi` carries `jakarta.validation-api` as an optional
-dependency and detects it at boot; without it the bridge class is never loaded.
-
-An explicit `@Schema` always wins — the bridge only fills keys nobody set.
-
-## Without Jackson
-
-`flash-ext-jackson` is optional. Without it `validate(value)` still works on values you construct
-or parse yourself; only `body(req, type)` needs a codec and says so if one is missing.
-
-## Performance
-
-The passing path is the one that runs on every request, so it allocates nothing:
-
- **Compiled once per type.** Constraints resolve to an opcode plus operands at first use, cached
-  in a `ClassValue` — stored beside the class by the JVM, so no map lookup, no lock, and the entry
-  is collected with the class rather than pinning it.
- **No reflection per request.** Fields are read through `MethodHandle`s adapted to an exact
-  signature: `(Object)Object` for references, `(Object)long` for primitive integrals. `invokeExact`
-  neither boxes nor builds the argument array that `Field.get` and `Method.invoke` allocate.
- **No megamorphic dispatch.** Checks are a flat array walked by a `tableswitch` on an opcode, not
-  a class hierarchy behind a virtual call.
- **No copies.** `@Size` reads a length the object already knows; `@Email` scans with `indexOf`
-  rather than a regex, because `Pattern.matcher` allocates a matcher and two int arrays per call.
- **Messages pre-rendered at compile time**, so even a failure formats nothing.
-
-The list, the violations and the exception exist only once something fails.
-
-`@Pattern` is the deliberate exception: its regex is compiled once, but `matcher()` allocates per
-call. It is marked in the source. Prefer `@Size`/`@Email` on hot routes, or validate the shape
-structurally.
-
-## Pre-warming
-
-Compilation happens on a type's first request. To pay it at boot instead:
-
-```java
-ctx.onReady(() -> ctx.require(Validation.class).forType(CreateUser.class));
-```
-
-Worth it only for a route that must not pay first-call cost. Everything else warms itself.
@@ -1,69 +0,0 @@
-package dev.relism.flash.ext.validation;
-
-import dev.relism.flash.ext.jackson.Json;
-import dev.relism.flash.models.Request;
-
-/**
- * The validation service. Resolve it with {@code require(Validation.class)}.
- *
- * <pre>{@code
- * CreateUser dto = validation.body(req, CreateUser.class);   // parse + verify
- * }</pre>
- *
- * <p>Constraints are compiled the first time a type is seen and cached in a {@link ClassValue},
- * which the JVM stores beside the class itself — no map lookup, no lock, and the entry is
- * collected with the class rather than pinning it. Every later request walks the compiled table.
- */
-public final class Validation {
-
-    private final ClassValue<Validator> validators = new ClassValue<>() {
-        @Override protected Validator computeValue(Class<?> type) {
-            return Validator.compile(type);
-        }
-    };
-
-    /** Null when flash-ext-jackson is absent; only {@link #body} needs it. */
-    private Json json;
-
-    Validation() {}
-
-    /** Called once at boot by {@link ValidationExtension}, after the service graph resolves. */
-    void bindCodec(Json json) {
-        this.json = json;
-    }
-
-    /**
-     * Deserializes the request body into {@code type} and verifies its constraints.
-     *
-     * @throws dev.relism.flash.exceptions.HttpException 400 if the body is not valid JSON
-     * @throws ValidationException 422 if it parses but violates a constraint
-     */
-    public <T> T body(Request request, Class<T> type) throws Exception {
-        if (json == null)
-            throw new IllegalStateException(
-                    "Validation.body(...) needs a JSON codec — install JacksonExtension, "
-                            + "or parse yourself and call validate(...)");
-        T value = json.body(request, type);
-        validators.get(type).verify(value);
-        return value;
-    }
-
-    /**
-     * Verifies an already-constructed value.
-     *
-     * @return {@code value}, so it can be used inline
-     * @throws ValidationException 422 on the first type's worth of failures
-     */
-    public <T> T validate(T value) {
-        validators.get(value.getClass()).verify(value);
-        return value;
-    }
-
-    /**
-     * The compiled constraints of {@code type}. Useful to pre-warm a hot DTO at boot, or to
-     * check whether a type declares constraints at all.
-     */
-    public Validator forType(Class<?> type) {
-        return validators.get(type);
-    }
-}
@@ -1,37 +0,0 @@
-package dev.relism.flash.ext.validation;
-
-import dev.relism.flash.ext.jackson.Json;
-import dev.relism.flash.extension.FlashContext;
-import dev.relism.flash.extension.FlashExtension;
-import dev.relism.flash.extension.FlashRegistrar;
-
-/**
- * Installs request validation.
- *
- * <pre>{@code
- * FlashApp.create(8080)
- *     .install(new JacksonExtension())
- *     .install(new ValidationExtension())
- *     .scan("dev.example.api");
- * }</pre>
- *
- * <p>No configuration. There is nothing to tune: constraints come from the annotations already on
- * your types, failures come back as 422 through Flash's default exception handler because
- * {@link ValidationException} carries its own status, and the JSON codec is picked up if
- * {@code flash-ext-jackson} is installed.
- *
- * <p>Install order does not matter — Flash resolves the whole service graph before any handler
- * initialises.
- */
-public final class ValidationExtension implements FlashExtension {
-
-    @Override
-    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
-        ctx.supply(Validation.class, Validation::new);
-
-        // Resolved here rather than declared as a dependency: jackson is optional, and a declared
-        // dependency would make it mandatory. By the time ready callbacks run the graph is
-        // complete, so find() sees whatever was actually installed.
-        ctx.onReady(() -> ctx.require(Validation.class).bindCodec(ctx.find(Json.class).orElse(null)));
-    }
-}
@@ -14,7 +14,9 @@
    <packaging>pom</packaging>

    <modules>
-        <module>flash-ext-jackson</module>
+        <module>flash-ext-jackson-core</module>
+        <module>flash-ext-jackson-json</module>
+        <module>flash-ext-jackson-xml</module>
        <module>flash-ext-openapi</module>
        <module>flash-ext-security-core</module>
        <module>flash-ext-security-oidc</module>
@@ -30,7 +32,6 @@
        <module>flash-ext-vite</module>
        <module>flash-ext-vite-maven-plugin</module>
        <module>flash-ext-mcp</module>
-        <module>flash-ext-validation</module>
        <module>flash-ext-scheduler</module>
        <module>flash-ext-data-core</module>
        <module>flash-ext-data-jdbc</module>
@@ -41,11 +42,6 @@

    <dependencyManagement>
        <dependencies>
-            <dependency>
-                <groupId>dev.relism</groupId>
-                <artifactId>flash-ext-validation</artifactId>
-                <version>${project.version}</version>
-            </dependency>
            <dependency>
                <groupId>dev.relism</groupId>
                <artifactId>flash-ext-scheduler</artifactId>
@@ -85,7 +81,17 @@
            </dependency>
            <dependency>
                <groupId>dev.relism</groupId>
-                <artifactId>flash-ext-jackson</artifactId>
+                <artifactId>flash-ext-jackson-core</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>dev.relism</groupId>
+                <artifactId>flash-ext-jackson-json</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>dev.relism</groupId>
+                <artifactId>flash-ext-jackson-xml</artifactId>
                <version>${project.version}</version>
            </dependency>
            <dependency>
@@ -98,6 +104,11 @@
                <artifactId>jackson-databind</artifactId>
                <version>2.17.2</version>
            </dependency>
+            <dependency>
+                <groupId>com.fasterxml.jackson.dataformat</groupId>
+                <artifactId>jackson-dataformat-xml</artifactId>
+                <version>2.17.2</version>
+            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.dataformat</groupId>
                <artifactId>jackson-dataformat-yaml</artifactId>