feat(ext-data): close the connection pool when the app stops

TxManager is AutoCloseable and releases what it was built on: JdbcTxManager its data
source when closeable, HibernateTxManager its session factory and then the data source
Hibernate was handed, which Hibernate itself never closes. DataExtension registers the
close as an onClose callback, so a stopped app no longer leaves its pool connected.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flash-extensions/flash-ext-data-hibernate/src/main/java/dev/relism/flash/ext/data/hibernate/HibernateTxManager.java

@@ -3,6 +3,10 @@ package dev.relism.flash.ext.data.hibernate;
 import dev.relism.flash.ext.data.core.*;
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
+import org.hibernate.engine.jdbc.connections.spi.ConnectionProvider;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+
+import javax.sql.DataSource;
 
 import java.util.Objects;
 
@@ -16,6 +20,24 @@ public class HibernateTxManager implements TxManager {
         this.sf = Objects.requireNonNull(sessionFactory);
     }
 
+    /**
+     * Closes the session factory, then the data source it was given ({@code jakarta.persistence.nonJtaDataSource}
+     * or {@code hibernate.connection.datasource}): Hibernate stops a pool it built itself, never one handed to it.
+     */
+    @Override
+    public void close() {
+        ConnectionProvider connections = sf.unwrap(SessionFactoryImplementor.class).getServiceRegistry().getService(ConnectionProvider.class);
+        DataSource ds = connections != null && connections.isUnwrappableAs(DataSource.class) ? connections.unwrap(DataSource.class) : null;
+        sf.close();
+        if (ds instanceof AutoCloseable closeable) {
+            try {
+                closeable.close();
+            } catch (Exception e) {
+                throw new IllegalStateException("Failed to close the data source", e);
+            }
+        }
+    }
+
     @Override
     public TxStatus begin(TxDefinition definition) {
         return switch (definition.propagation()) {

flash-extensions/flash-ext-data-hibernate/src/test/java/dev/relism/flash/ext/data/hibernate/HibernateTxManagerCloseTest.java

@@ -0,0 +1,48 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import org.hibernate.SessionFactory;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.AvailableSettings;
+import org.junit.jupiter.api.Test;
+
+import javax.sql.DataSource;
+import java.io.PrintWriter;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.util.logging.Logger;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class HibernateTxManagerCloseTest {
+
+    /** Stands in for a pool: closeable, and it records being closed. */
+    static final class Pool implements DataSource, AutoCloseable {
+        boolean closed;
+        @Override public Connection getConnection() throws SQLException { return DriverManager.getConnection("jdbc:h2:mem:tx-close;DB_CLOSE_DELAY=-1"); }
+        @Override public Connection getConnection(String user, String password) throws SQLException { return getConnection(); }
+        @Override public void close() { closed = true; }
+        @Override public <T> T unwrap(Class<T> type) { throw new UnsupportedOperationException(); }
+        @Override public boolean isWrapperFor(Class<?> type) { return false; }
+        @Override public PrintWriter getLogWriter() { return null; }
+        @Override public void setLogWriter(PrintWriter out) {}
+        @Override public void setLoginTimeout(int seconds) {}
+        @Override public int getLoginTimeout() { return 0; }
+        @Override public Logger getParentLogger() { throw new UnsupportedOperationException(); }
+    }
+
+    @Test
+    void closingTheManagerClosesTheDataSourceHibernateWasGiven() {
+        Pool pool = new Pool();
+        SessionFactory sf = new MetadataSources(new StandardServiceRegistryBuilder()
+                .applySetting(AvailableSettings.JAKARTA_NON_JTA_DATASOURCE, pool)
+                .applySetting(AvailableSettings.DIALECT, "org.hibernate.dialect.H2Dialect")
+                .build()).buildMetadata().buildSessionFactory();
+
+        new HibernateTxManager(sf).close();
+
+        assertTrue(sf.isClosed());
+        assertTrue(pool.closed);
+    }
+}