Extending IG Through the Java API

Key Extension Points

Interface Stability: Evolving, as defined in "ForgeRock Product Stability Labels".

Implementing a Customized Sample Filter

The SampleFilter class implements the Filter interface to set a header in the incoming request and in the outgoing response.

In the following example, the sample filter adds an arbitrary header:

package org.forgerock.openig.doc.examples;

import org.forgerock.http.Filter;
import org.forgerock.http.Handler;
import org.forgerock.http.protocol.Request;
import org.forgerock.http.protocol.Response;
import org.forgerock.openig.heap.GenericHeaplet;
import org.forgerock.openig.heap.HeapException;
import org.forgerock.services.context.Context;
import org.forgerock.util.promise.NeverThrowsException;
import org.forgerock.util.promise.Promise;

/**
 * Filter to set a header in the incoming request and in the outgoing response.
 */
public class SampleFilter implements Filter {

    /** Header name. */
    String name;

    /** Header value. */
    String value;

    /**
     * Set a header in the incoming request and in the outgoing response.
     * A configuration example looks something like the following.
     *
     * <pre>
     * {
     *     "name": "SampleFilter",
     *     "type": "SampleFilter",
     *     "config": {
     *         "name": "X-Greeting",
     *         "value": "Hello world"
     *     }
     * }
     * </pre>
     *
     * @param context           Execution context.
     * @param request           HTTP Request.
     * @param next              Next filter or handler in the chain.
     * @return A {@code Promise} representing the response to be returned to the client.
     */
    @Override
    public Promise<Response, NeverThrowsException> filter(final Context context,
                                                          final Request request,
                                                          final Handler next) {

        // Set header in the request.
        request.getHeaders().put(name, value);

        // Pass to the next filter or handler in the chain.
        return next.handle(context, request)
                   // When it has been successfully executed, execute the following callback
                   .thenOnResult(response -> {
                       // Set header in the response.
                       response.getHeaders().put(name, value);
                   });
    }

    /**
     * Create and initialize the filter, based on the configuration.
     * The filter object is stored in the heap.
     */
    public static class Heaplet extends GenericHeaplet {

        /**
         * Create the filter object in the heap,
         * setting the header name and value for the filter,
         * based on the configuration.
         *
         * @return                  The filter object.
         * @throws HeapException    Failed to create the object.
         */
        @Override
        public Object create() throws HeapException {

            SampleFilter filter = new SampleFilter();
            filter.name  = config.get("name").as(evaluatedWithHeapProperties()).required().asString();
            filter.value = config.get("value").as(evaluatedWithHeapProperties()).required().asString();

            return filter;
        }
    }
}

The corresponding filter configuration is similar to this:

{
  "name": "SampleFilter",
  "type": "org.forgerock.openig.doc.examples.SampleFilter",
  "config": {
    "name": "X-Greeting",
    "value": "Hello world"
  }
}

Note how type is configured with the fully qualified class name for SampleFilter. To simplify the configuration, implement a class alias resolver, as described in "Implementing a Class Alias Resolver".

Implementing a Class Alias Resolver

To simplify the configuration of a customized object, implement a ClassAliasResolver to allow the use of short names instead of fully qualified class names.

In the following example, a ClassAliasResolver is created for the SampleFilter class:

package org.forgerock.openig.doc.examples;

import java.util.HashMap;
import java.util.Map;

import org.forgerock.openig.alias.ClassAliasResolver;

/**
 * Allow use of short name aliases in configuration object types.
 *
 * This allows a configuration with {@code "type": "SampleFilter"}
 * instead of {@code "type": "org.forgerock.openig.doc.examples.SampleFilter"}.
 */
public class SampleClassAliasResolver implements ClassAliasResolver {

    private static final Map<String, Class<?>> ALIASES =
            new HashMap<>();

    static {
        ALIASES.put("SampleFilter", SampleFilter.class);
    }

    /**
     * Get the class for a short name alias.
     *
     * @param alias Short name alias.
     * @return      The class, or null if the alias is not defined.
     */
    @Override
    public Class<?> resolve(final String alias) {
        return ALIASES.get(alias);
    }
}

With this ClassAliasResolver, the filter configuration in "Implementing a Customized Sample Filter" can use the alias instead of the fully qualified class name, as follows:

{
  "name": "SampleFilter",
  "type": "SampleFilter",
  "config": {
    "name": "X-Greeting",
    "value": "Hello world"
  }
}

To create a customized ClassAliasResolver, add a services file with the following characteristics:

Configuring the Heap Object for the Customization

Objects are added to the heap and supplied with configuration artifacts at initialization time. To be integrated with the configuration, a class must have an accompanying implementation of the Heaplet interface. The easiest and most common way of exposing the heaplet is to extend the GenericHeaplet class in a nested class of the class you want to create and initialize, overriding the heaplet's create() method.

Within the create() method, you can access the object's configuration through the config field.

Embedding the Customization in IG

After building your customizations into a .jar file, add it to the configuration as follows: