Jersey 2.0 的依赖注入 [英] Dependency injection with Jersey 2.0

问题描述

从零开始，之前没有任何 Jersey 1.x 知识，我很难理解如何在我的 Jersey 2.0 项目中设置依赖注入.

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.

我也知道 HK2 在 Jersey 2.0 中可用，但我似乎找不到有助于 Jersey 2.0 集成的文档.

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>

我可以让容器启动并提供我的资源，但是一旦我将@Inject 添加到 MyService，框架就会抛出异常:

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)

我的入门项目可在 GitHub 上找到:https://github.com/donaldjarmstrong/jaxrs

推荐答案

您需要定义一个 AbstractBinder 并将其注册到您的 JAX-RS 应用程序中.活页夹指定依赖注入应如何创建您的类.

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);
    }
}

当在MyService.class 类型的参数或字段上检测到@Inject 时，它会使用MyService 类进行实例化.要使用这个绑定器，它需要在 JAX-RS 应用程序中注册.在您的 web.xml 中，定义一个 JAX-RS 应用程序，如下所示:

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>

实现 MyApplication 类(在上面的 init-param 中指定).

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");
    }
}

指定依赖注入的绑定器在类的构造函数中注册，我们还使用 packages() 方法调用.

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.

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