Using the Guice Struts 2 plugin

03/29/2011

Guice 3.0 was released a few days ago!  One of the easiest ways to use it in your web server is to use Struts 2 with the Struts 2 plugin, which is available in the central Maven repository.

This tutorial assumes familiarity with Guice and Struts 2.

In order to use it the plugin, your injector must be created with a Struts2GuicePluginModule:

Injector injector = Guice.createInjector(
    new com.google.inject.servlet.ServletModule(),
    new com.google.inject.struts2.Struts2GuicePluginModule(),
    new MyModule());

You must then define a GuiceServletContextListener to provide the injector to the Struts 2 plugin. I injected the Injector because I’m using embedded Jetty. However, if you’re using a standard servlet container, you’d probably just create the injector in the class itself.

package com.benmccann.example;

import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.servlet.GuiceServletContextListener;

/**
 * @author benmccann.com
 */
public class GuiceListener extends GuiceServletContextListener {

  private final Injector injector;

  @Inject
  public GuiceListener(Injector injector) {
    this.injector = injector;
  }

  @Override
  public Injector getInjector() {
    return injector;
  }

}

You must then wire it up in your web.xml:

  <listener>
    <listener-class>com.benmccann.example.GuiceListener</listener-class>
  </listener>  

  <filter>
    <filter-name>guice</filter-name>
    <filter-class>com.google.inject.servlet.GuiceFilter</filter-class>
  </filter>

  <filter-mapping>
    <filter-name>guice</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

There’s also an example in the Guice source code repository.

Enjoy!