泽西岛的依赖注入

Question

如果我使用Jersey 1.12,并且我有多个资源类,并且它们都需要访问一些共享上下文,那么注入依赖项的最佳方法是什么,无论是在资源类的构造函数中还是在处理程序方法中？我是否需要使用外部DI库,或者Jersey内置了什么？

也许Foos的资源看起来像这样:

package com.example.resource;

import javax.ws.rs.GET;
import javax.ws.rs.Produces;
import javax.ws.rs.Path;

@Path("/some/api/path/foo")
public class FooResource
{
    @GET
    @Produces("text/html")
    public String getFoo(@QueryParam("id") String id)
    {
        Foo foo = /* get a Foo from some shared context based on id */
        /* Process foo into a String */
    }
}

和酒吧:

package com.example.resource;

import javax.ws.rs.GET;
import javax.ws.rs.Produces;
import javax.ws.rs.Path;

@Path("/some/api/path/bar")
public class BarResource
{
    @GET
    @Produces("text/html")
    public String getBar(@QueryParam("id") String id)
    {
        Bar bar = /* get a Bar from some shared context based on id */
        /* Process bar into a String */
    }
}

Answer 1

我最终使用了Google Guice,这是一个轻量级的DI框架,可以很好地与Jersey集成.这就是我必须做的事情:

首先,我在pom.xml中添加了依赖项:

    <dependency>
        <groupId>com.google.inject</groupId>
        <artifactId>guice</artifactId>
        <version>3.0</version>
        <scope>compile</scope>
    </dependency>
    <dependency>
        <groupId>com.sun.jersey.contribs</groupId>
        <artifactId>jersey-guice</artifactId>
        <version>1.12</version>
        <scope>compile</scope>
    </dependency>

我希望将DAO实现为具有接口的单例:

public interface MySingletonDao
{
    // ... methods go here ...
}

和具体的实施:

@Singleton
public class ConcreteMySingletonDao implements MySingletonDao
{
    // ... methods go here ...
}

像这样装饰资源类:

@Path("/some/path")
@RequestScoped
public class MyResource
{
    private final MySingletonDao mySingletonDao;

    @Inject
    public MyResource(MySingletonDao mySingletonDao)
    {
        this.mySingletonDao = mySingletonDao;
    }

    @POST
    @Produces("application/json")
    public String post() throws Exception
    {
            // ... implementation goes here ...
    }
}

创建了一个将执行绑定的类:

public class GuiceConfig extends GuiceServletContextListener
{
    @Override
    protected Injector getInjector()
    {
        return Guice.createInjector(new JerseyServletModule()
        {
            @Override
            protected void configureServlets()
            {
                bind(MyResource.class);
                bind(AnotherResource.class);
                bind(MySingletonDao.class).to(ConcreteMySingletonDao.class);
                serve("/*").with(GuiceContainer.class);
            }
        });
    }
}

我使用Jetty而不是Glassfish来实际充当服务器.在我的功能测试中,它看起来像:

private void startServer() throws Exception
{
    this.server = new Server(8080);
    ServletContextHandler root =
        new ServletContextHandler(server, "/", ServletContextHandler.SESSIONS);

    root.addEventListener(new GuiceConfig());
    root.addFilter(GuiceFilter.class, "/*", EnumSet.of(DispatcherType.REQUEST));
    root.addServlet(EmptyServlet.class, "/*");

    this.server.start();
}

在EmptyServlet来自给出了一个答案,在欣格里森的示例代码:/sf/answers/230752721/ -我本来

root.addServlet(new ServletHolder(new ServletContainer(new PackagesResourceConfig("com.example.resource"))), "/*");

而不是线

root.addServlet(EmptyServlet.class, "/*");

但是这导致Jersey尝试执行依赖注入而不是Guice,这会导致运行时错误.