Using Guice with Cloud Endpoints Frameworks

Google Guice is a dependency injection framework that you can use with an Endpoints Frameworks v2 project to configure servlet mapping and filtering programmatically in Java, rather than in web.xml .

To use Guice, you need to add the following prepackaged dependency to your pom.xml or build.gradle . Also, you need to configure the Endpoints Frameworks plugins for Maven and Gradle to define which service classes the plugins use to create OpenAPI documents.

Maven

 <dependency>  
<groupId>com.google.endpoints</groupId>  
<artifactId>endpoints-framework-guice</artifactId>  
<version>2.2.2</version>
</dependency>

Gradle

  compile 
  
 'com.google.endpoints:endpoints-framework-guice:2.2.2'

  endpointsServer 
  
 { 
  
 // Endpoints Framework Plugin server-side configuration 
  
 hostname 
  
 = 
  
 "${projectId}.appspot.com" 
  
 serviceClasses 
  
 = 
  
 [ 
 'com.example.echo.Echo' 
 ] 
 }

Next, you need to update web.xml to direct all traffic from /_ah/api/* to the Endpoints Frameworks Guice Servlet.

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

<!--  
URL  
Pattern  
/_ah/api/*  
instead  
of  
/*  
because  
a  
legacy  
v1  
servlet  
uses  
the  
route  
/_ah/api/  
and  
using  
/*  
will  
erronously  
use  
the  
legacy  
v1  
servlet  
instead  
of  
routing  
to  
your  
API.
-->
<filter-mapping>  
<filter-name>guiceFilter</filter-name>  
<url-pattern>/_ah/api/*</url-pattern>
</filter-mapping>

<listener>  
<listener-class>com.example.echo.EchoGuiceListener</listener-class>
</listener>

Implement the listener class in your project. It should look similar to the following depending on the number of services:

  public 
  
 class 
 EchoGuiceListener 
  
 extends 
  
 GuiceServletContextListener 
  
 { 
  
 @Override 
  
 protected 
  
 Injector 
  
 getInjector 
 () 
  
 { 
  
 return 
  
 Guice 
 . 
 createInjector 
 ( 
 new 
  
 EchoEndpointModule 
 ()); 
  
 } 
 }

The listener class creates a new injector that handles servlet mapping and filtering, which is normally defined by the web.xml , but instead is now defined by the EchoEndpointModule class defined as:

  public 
  
 class 
 EchoEndpointModule 
  
 extends 
  
 EndpointsModule 
  
 { 
  
 @Override 
  
 public 
  
 void 
  
 configureServlets 
 () 
  
 { 
  
 super 
 . 
 configureServlets 
 (); 
  
 bind 
 ( 
 ServiceManagementConfigFilter 
 . 
 class 
 ). 
 in 
 ( 
 Singleton 
 . 
 class 
 ); 
  
 filter 
 ( 
 "/_ah/api/*" 
 ). 
 through 
 ( 
 ServiceManagementConfigFilter 
 . 
 class 
 ); 
  
 Map<String 
 , 
  
 String 
>  
 apiController 
  
 = 
  
 new 
  
 HashMap 
<> (); 
  
 apiController 
 . 
 put 
 ( 
 "endpoints.projectId" 
 , 
  
 "YOUR-PROJECT-ID" 
 ); 
  
 apiController 
 . 
 put 
 ( 
 "endpoints.serviceName" 
 , 
  
 "YOUR-PROJECT-ID.appspot.com" 
 ); 
  
 bind 
 ( 
 GoogleAppEngineControlFilter 
 . 
 class 
 ). 
 in 
 ( 
 Singleton 
 . 
 class 
 ); 
  
 filter 
 ( 
 "/_ah/api/*" 
 ). 
 through 
 ( 
 GoogleAppEngineControlFilter 
 . 
 class 
 , 
  
 apiController 
 ); 
  
 bind 
 ( 
 Echo 
 . 
 class 
 ). 
 toInstance 
 ( 
 new 
  
 Echo 
 ()); 
  
 configureEndpoints 
 ( 
 "/_ah/api/*" 
 , 
  
 ImmutableList 
 . 
 of 
 ( 
 Echo 
 . 
 class 
 )); 
  
 } 
 }

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Using Guice with Cloud Endpoints Frameworks