使用Jersey 2.0进行依赖注入

Question

从头开始没有任何以前的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.

我也明白HK2可用于Jersey 2.0,但我似乎无法找到有助于Jersey 2.0集成的文档.

@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");
    }
}

的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,但是只要我将@Inject添加到MyService,框架就会抛出异常:

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)

我的初学者项目可以在GitHub上找到:https://github.com/donaldjarmstrong/jaxrs

Answer 1

您需要AbstractBinder在JAX-RS应用程序中定义并注册它.绑定器指定依赖注入应如何创建类.

public class MyApplicationBinder extends AbstractBinder {
    @Override
    protected void configure() {
        bind(MyService.class).to(MyService.class);
    }
}

当@Inject在类型的参数或字段上检测到MyService.class它时,使用该类对其进行实例化MyService.要使用此绑定程序,需要在JAX-RS应用程序中注册.在您的web.xml定义JAX-RS应用程序中,如下所示:

<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(在上面指定init-param).

public class MyApplication extends ResourceConfig {
    public MyApplication() {
        register(new MyApplicationBinder());
        packages(true, "com.mypackage.rest");
    }
}

指定依赖项注入的绑定器在类的构造函数中注册,我们还MyResource使用packages()方法调用告诉应用程序在何处查找REST资源(在您的情况下).

Answer 2

首先只是回答接受答案中的评论.

"绑定做什么？如果我有接口和实现怎么办？"

它只是读bind( implementation ).to( contract ).你可以替代链.in( scope ).默认范围PerLookup.所以,如果你想要一个单身人士,你可以

bind( implementation ).to( contract ).in( Singleton.class );

还有一个RequestScoped可用的

另外,bind(Class).to(Class)您也bind(Instance).to(Class)可以自动成为单身人士.

添加到已接受的答案

对于那些试图弄清楚如何AbstractBinder在web.xml中注册实现的人(即你没有使用a ResourceConfig),似乎不会通过包扫描发现绑定器,即

<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
    <param-name>jersey.config.server.provider.packages</param-name>
    <param-value>
        your.packages.to.scan
    </param-value>
</init-param>

或者这个

<init-param>
    <param-name>jersey.config.server.provider.classnames</param-name>
    <param-value>
        com.foo.YourBinderImpl
    </param-value>
</init-param>

为了让它工作,我不得不实现Feature:

import javax.ws.rs.core.Feature;
import javax.ws.rs.core.FeatureContext;
import javax.ws.rs.ext.Provider;

@Provider
public class Hk2Feature implements Feature {

    @Override
    public boolean configure(FeatureContext context) {
        context.register(new AppBinder());
        return true;
    }
}

该@Provider注释应允许Feature由包扫描被拾起.或者没有包扫描,你可以明确地登记Feature在web.xml

<servlet>
    <servlet-name>Jersey Web Application</servlet-name>
    <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
    <init-param>
        <param-name>jersey.config.server.provider.classnames</param-name>
        <param-value>
            com.foo.Hk2Feature
        </param-value>
    </init-param>
    ...
    <load-on-startup>1</load-on-startup>
</servlet>

也可以看看:

• 使用Jersey定制方法参数注入
• 如何将对象注入泽西请求上下文？
• 如何在jersey/hk2应用程序中正确配置EntityManager？
• 请求将单一注射注入单身人士

以及来自Jersey文档的一般信息

• 自定义注入和生命周期管理

UPDATE

工厂

除了已接受答案中的基本绑定外,您还拥有工厂,您可以在其中拥有更复杂的创建逻辑,还可以访问请求上下文信息.例如

public class MyServiceFactory implements Factory<MyService> {
    @Context
    private HttpHeaders headers;

    @Override
    public MyService provide() {
        return new MyService(headers.getHeaderString("X-Header"));
    }

    @Override
    public void dispose(MyService service) { /* noop */ }
}

register(new AbstractBinder() {
    @Override
    public void configure() {
        bindFactory(MyServiceFactory.class).to(MyService.class)
                .in(RequestScoped.class);
    }
});

然后你可以注入MyService你的资源类.

Answer 3

选定的答案可以追溯到前一段时间.在自定义HK2活页夹中声明每个绑定是不切实际的.我正在使用Tomcat,我只需添加一个依赖项.尽管它是专为Glassfish设计的,但它完全适合其他容器.

   <dependency>
        <groupId>org.glassfish.jersey.containers.glassfish</groupId>
        <artifactId>jersey-gf-cdi</artifactId>
        <version>${jersey.version}</version>
    </dependency>

确保您的容器也已正确配置(请参阅文档).

Answer 4

迟到但我希望这有助于某人.

我的JAX RS定义如下:

@Path("/examplepath")
@RequestScoped //this make the diference
public class ExampleResource {

然后,在我的代码中,我最终可以注入:

@Inject
SomeManagedBean bean;

就我而言,它SomeManagedBean是一个ApplicationScoped bean.

希望这对任何人都有帮助.