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## Chapter 48. Guice 3.0 Integration

RESTEasy has some simple integration with Guice 3.0. RESTEasy will scan the binding types for a Guice Module for @Path and @Provider annotations. It will register these bindings with RESTEasy. The guice-hello project that comes in the RESTEasy examples/ directory gives a nice example of this.

    @Path("hello")
    public class HelloResource
    {
       @GET
       @Path("{name}")
       public String hello(@PathParam("name") final String name) {
          return "Hello " + name;
       }
    }

First you start off by specifying a JAX-RS resource class. The HelloResource is just that. Next you create a Guice Module class that defines all your bindings:

    import com.google.inject.Module;
    import com.google.inject.Binder;

    public class HelloModule implements Module
    {
        public void configure(final Binder binder)
        {
           binder.bind(HelloResource.class);
        }
    }

You put all these classes somewhere within your WAR WEB-INF/classes or in a JAR within WEB-INF/lib. Then you need to create your web.xml file. You need to use the GuiceResteasyBootstrapServletContextListener as follows

    <web-app>
        <display-name>Guice Hello</display-name>

        <context-param>
            <param-name>resteasy.guice.modules</param-name>
            <param-value>org.jboss.resteasy.examples.guice.hello.HelloModule</param-value>
        </context-param>

        <listener>
            <listener-class>
                org.jboss.resteasy.plugins.guice.GuiceResteasyBootstrapServletContextListener
            </listener-class>
        </listener>

        <servlet>
            <servlet-name>Resteasy</servlet-name>
            <servlet-class>
                org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
            </servlet-class>
        </servlet>

        <servlet-mapping>
            <servlet-name>Resteasy</servlet-name>
            <url-pattern>/*</url-pattern>
        </servlet-mapping>

    </web-app>

GuiceResteasyBootstrapServletContextListener is a subclass of ResteasyBootstrap, so you can use any other RESTEasy configuration option within your web.xml file. Also notice that there is a resteasy.guice.modules context-param. This can take a comma delimited list of class names that are Guice Modules.

## 48.1. Request Scope

Add the RequestScopeModule to your modules to allow objects to be scoped to the HTTP request by adding the @RequestScoped annotation to your class. All the objects injectable via the @Context annotation are also injectable, except ServletConfig and ServletContext.

    import javax.inject.Inject;
    import javax.servlet.http.HttpServletRequest;
    import javax.ws.rs.core.Context;

    import org.jboss.resteasy.plugins.guice.RequestScoped;

    @RequestScoped
    public class MyClass
    {
        @Inject @Context
        private HttpRequest request;
    }

## 48.2. Binding JAX-RS utilities

Add the JaxrsModule to bind javax.ws.rs.ext.RuntimeDelegate, javax.ws.rs.core.Response.ResponseBuilder, javax.ws.rs.core.UriBuilder, javax.ws.rs.core.Variant.VariantListBuilder and org.jboss.resteasy.client.ClientExecutor.

## 48.3. Configuring Stage

You can configure the stage Guice uses to deploy your modules by specific a context param, resteasy.guice.stage. If this value is not specified, Resteasy uses whatever Guice's default is.

    <web-app>
        <display-name>Guice Hello</display-name>

        <context-param>
            <param-name>resteasy.guice.modules</param-name>
            <param-value>org.jboss.resteasy.examples.guice.hello.HelloModule</param-value>
        </context-param>

        <context-param>
            <param-name>resteasy.guice.stage</param-name>
            <param-value>PRODUCTION</param-value>
        </context-param>

        <listener>
            <listener-class>
                org.jboss.resteasy.plugins.guice.GuiceResteasyBootstrapServletContextListener
            </listener-class>
        </listener>

        <servlet>
            <servlet-name>Resteasy</servlet-name>
            <servlet-class>
                org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
            </servlet-class>
        </servlet>

        <servlet-mapping>
            <servlet-name>Resteasy</servlet-name>
            <url-pattern>/*</url-pattern>
        </servlet-mapping>

    </web-app>

## 48.4. Custom Injector creation

GuiceResteasyBootstrapServletContextListener can be extended to allow more flexibility in the way the Injector and Modules are created. Three methods can be overridden: getModules(), withInjector() and getStage(). Register your subclass as the listener in the web.xml.

Override getModules() when you need to pass arguments to your modules' constructor or perform more complex operations.

Override withInjector(Injector) when you need to interact with the Injector after it has been created.

Override getStage(ServletContext) to set the Stage yourself.

    <web-app>
        <!-- other tags omitted -->
        <listener>
          <listener-class>
             org.jboss.resteasy.plugins.guice.GuiceResteasyBootstrapServletContextListener
          </listener-class>
        </listener>
    </web-app>

    public class MyServletContextListener extends GuiceResteasyBootstrapServletContextListener
    {

        @Override
        protected List<? extends Module> getModules(ServletContext context)
        {
            return Arrays.asList(new JpaPersistModule("consulting_hours"), new MyModule());
        }

        @Override
        public void withInjector(Injector injector)
        {
            injector.getInstance(PersistService.class).start();
        }
    }

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