PixelDocs/flash/dynamic-file-server.md

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Flash - Dynamic File Server	Learn how to serve files in a dynamic context.

📁 Dynamic File Server

Sometimes we need to serve files in a dynamic context, in this sense a static file server is limiting. Imagine we have a frontend application that is compiled down to a single index.html file, and we want to serve it with Flash alongside it's javascript and css bundles. The way these compiled applications work is that they rely heavily on client-side routing, so when the user navigates to a different page, the frontend application will try to fetch the corresponding file from the server. This is where a dynamic file server comes in handy, as no route is pre-registered.

::: warning The dynamic file server relies heavily on the concept of dynamic handlers, which are handlers that will resolve for any subpath of the endpoint they are registered to (see Handler Types for more info). :::

Usage

To serve static files in Flash, you need to call the server.serveDynamic() method with the endpoint path and an instance of DynamicFileServerConfig. The configuration object is instanced like so :

DynamicFileServerConfiguration(
    boolean enableFileWatcher,
    String destinationPath,
    String dynamicEntrypoint,
    SourceType sourceType
)

• enableFileWatcher : If set to true, the server will watch for changes in the served files and reload them automatically.
• destinationPath : The path to the directory containing the files to be served.
• dynamicEntrypoint : The path to the file that will be served when the client navigates to the endpoint eg. index.html.
• sourceType : The type of source to serve files from. It can be either FILESYSTEM or RESOURCESTREAM.

Registering the dynamic file server is as simple as calling the server.serveDynamic() method with the desired path and configuration object:

public class Example {
    public static void main(String[] args) {
        FlashServer server = new FlashServer(8080);

        server.serveDynamic("/*", new DynamicFileServerConfiguration(
            true,
            "path/to/my/files",
            "index.html",
            SourceType.FILESYSTEM
        ));
    }
}

Now you can access the files (or frontend) in the specified directory by navigating to http://localhost:8080/<file-name>.

Similarly, you can serve the same content from the jar's resources folder by setting the sourceType to RESOURCESTREAM:

public class Example {
    public static void main(String[] args) {
        FlashServer server = new FlashServer(8080);

        server.serveStatic("/static", new DynamicFileServerConfiguration(
            true,
            "path/to/my/files",
            "index.html",
            SourceType.RESOURCESTREAM
        ));
    }
}

💻 Note on Fullstack Development

The dynamic file server opens up the possibility for fullstack development with Flash. You can easily serve your frontend application alongside your backend, and build the entire application in a single jarfile.

This is possible thanks to the RESOURCESTREAM source type, which allows you to serve files from the jar's resources folder: the ideal cycle for packaging your app would be to compile the frontend application and place the compiled files in the resources folder (or setup the build script to do it for you), then build the jarfile with the compiled frontend and the backend code.

This approach works for any frontend framework that can compile down to static files (React, Angular, Vue, etc.).

For more in-depth information on how to build a fullstack application with Flash, check out the Fullstack Development guide.