Dependency injection with Jersey 2.0
dependency-injection, hk2, java, jersey, jersey-2.0
Solution
You need to define an `AbstractBinder` and register it in your JAX-RS application. The binder specifies how the dependency injection should create your classes.
public class MyApplicationBinder extends AbstractBinder {
@Override
protected void configure() {
bind(MyService.class).to(MyService.class);
}
}
When `@Inject` is detected on a parameter or field of type `MyService.class` it is instantiated using the class `MyService`. To use this binder, it need to be registered with the JAX-RS application. In your `web.xml`, define a JAX-RS application like this:
<servlet>
<servlet-name>MyApplication</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>javax.ws.rs.Application</param-name>
<param-value>com.mypackage.MyApplication</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>MyApplication</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
Implement the `MyApplication` class (specified above in the `init-param`).
public class MyApplication extends ResourceConfig {
public MyApplication() {
register(new MyApplicationBinder());
packages(true, "com.mypackage.rest");
}
}
The binder specifying dependency injection is registered in the constructor of the class, and we also tell the application where to find the REST resources (in your case, `MyResource`) using the `packages()` method call.
Problem
Starting from scratch without any previous Jersey 1.x knowledge, I'm having a hard time understanding how to setup dependency injection in my Jersey 2.0 project. I also understand that HK2 is available in Jersey 2.0, but I cannot seem to find docs that help with Jersey 2.0 integration. ``` @ManagedBean @Path("myresource") public class MyResource { @Inject MyService myService; /** * Method handling HTTP GET requests. The returned object will be sent * to the client as "text/plain" media type. * * @return String that will be returned as a text/plain response. */ @GET @Produces(MediaType.APPLICATION_JSON) @Path("/getit") public String getIt() { return "Got it {" + myService + "}"; } } @Resource @ManagedBean public class MyService { void serviceCall() { System.out.print("Service calls"); } } ``` pom.xml ``` <properties> <jersey.version>2.0-rc1</jersey.version> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencyManagement> <dependencies> <dependency> <groupId>org.glassfish.jersey</groupId> <artifactId>jersey-bom</artifactId> <version>${jersey.version}</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> <dependencies> <dependency> <groupId>org.glassfish.jersey.core</groupId> <artifactId>jersey-common</artifactId> </dependency> <dependency> <groupId>org.glassfish.jersey.core</groupId> <artifactId>jersey-server</artifactId> </dependency> <dependency> <groupId>org.glassfish.jersey</groupId> <artifactId>jax-rs-ri</artifactId> </dependency> </dependencies> ``` I can get the container to start and serve up my resource, but as soon as I add @Inject to MyService, the framework throws an exception: ``` SEVERE: Servlet.service() for servlet [com.noip.MyApplication] in context with path [/jaxrs] threw exception [A MultiException has 3 exceptions. They are: 1. org.glassfish.hk2.api.UnsatisfiedDependencyException: There was no object available for injection at Injectee(requiredType=MyService,parent=MyResource,qualifiers={}),position=-1,optional=false,self=false,unqualified=null,1039471128) 2. java.lang.IllegalArgumentException: While attempting to resolve the dependencies of com.noip.MyResource errors were found 3. java.lang.IllegalStateException: Unable to perform operation: resolve on com.noip.MyResource ] with root cause org.glassfish.hk2.api.UnsatisfiedDependencyException: There was no object available for injection at Injectee(requiredType=MyService,parent=MyResource,qualifiers={}),position=-1,optional=false,self=false,unqualified=null,1039471128) at org.jvnet.hk2.internal.ThreeThirtyResolver.resolve(ThreeThirtyResolver.java:74) ``` My starter project is available at GitHub: https://github.com/donaldjarmstrong/jaxrs