add Guice section

Author: decebals

_posts/2015-05-27-guice.md

@@ -0,0 +1,76 @@
+---
+layout: page
+title: "Guice"
+category: mod
+date: 2015-05-27 15:27:38
+order: 15
+---
+
+Pippo can be used together with the [Guice](https://github.com/google/guice), using Guice as a dependency injection container.  
+When Pippo creates new instances of your various `Controller` subclasses it delegates the instance creation to a `ControllerFactory`.
+The module [pippo-guice]({{ site.codeurl }}/pippo-guice) contains [GuiceControllerFactory]({{ site.codeurl }}/pippo-guice/src/main/java/ro/pippo/guice/GuiceControllerFactory.java) that it's 
+a `ControllerFactory` implementation that delegates to the Guice container to instantiate a given `Controller` class. This allows for the instance to be configured via dependency injection.
+
+An example of such a Controller subclass could look as follows:
+
+```java
+public class ContactsController extends Controller {
+
+    @Inject
+    private ContactService contactService;
+
+    public void index() {
+		List<Contact> contacts = contactService.getContacts()
+        getResponse().bind("contacts", contacts).render("contacts");
+    }
+
+}
+```
+
+Pippo automatically creates the _ContactsController_ instance and pippo-guice injects the ContactService service bean, so basically you don’t have to worry about any of that stuff. 
+
+To activate pippo-guice integration in your Application you must add `GuiceControllerFactory`:
+
+```java
+public class MyApplication extends Application {
+
+    @Override
+    protected void onInit() {
+        // create guice injector
+        Injector injector = Guice.createInjector(new GuiceModule());
+
+        // registering GuiceControllerFactory
+        setControllerFactory(new GuiceControllerFactory(injector));
+
+        // add controller
+        GET("/", ContactsController.class, "index");        
+    }
+
+}
+```
+
+where `GuiceModule` can looks like:
+
+```java
+public class GuiceModule extends AbstractModule {
+
+	@Override
+	protected void configure() {
+		bind(ContactService.class).to(InMemoryContactService.class).asEagerSingleton();
+	}
+
+}
+```
+
+Also don't forget to add pippo-guice as dependency in your project:
+
+```xml
+<dependency>
+    <groupId>ro.pippo</groupId>
+    <artifactId>pippo-guice</artifactId>
+    <version>${pippo.version}</version>
+</dependency>
+```
+
+You can see a demo [here]({{ site.demourl }}/pippo-demo-guice)
+