java – 自定义提供程序无法注入过滤器

2019年8月4日 162次阅读

我有一个POJO,我想注入资源和过滤器：

public final class MyObject { }

我为它实现了一个自定义提供程序：

@Provider
public final class MyProvider
extends AbstractHttpContextInjectable<MyObject>
implements InjectableProvider<Context, Type> {

    @Context private HttpServletRequest request;

    @Override
    public Injectable<MyObject> getInjectable(
            ComponentContext componentContext,
            Context annotation,
            Type type
    ) {
        if (type.equals(MyObject.class)) {
            return this;
        }
        return null;
    }

    @Override
    public ComponentScope getScope() {
        return ComponentScope.PerRequest;
    }

    @Override
    public MyObject getValue(HttpContext httpContext) {
        //in reality, use session info from injected request to create MyObject
        return new MyObject();
    }
}

该对象已成功注入我的资源：

@Path("/test")
@ResourceFilters(MyFilter.class)
public final class MyResource {

    @Context private HttpServletRequest request;
    @Context private MyObject myObject;

    @GET
    public String execute() {

        System.out.println(request != null);  //true
        System.out.println(myObject != null); //true

        return "data";
    }
}

但泽西岛未能将其注入我的过滤器：

public final class MyFilter implements ResourceFilter {

    @Context private HttpServletRequest request;
    @Context private MyObject myObject;

    @Override
    public ContainerRequestFilter getRequestFilter() {
        return new ContainerRequestFilter() {
            @Override
            public ContainerRequest filter(ContainerRequest containerRequest) {

                System.out.println(request != null);  //true
                System.out.println(myObject != null); //false

                return containerRequest;
            }
        };
    }

    @Override
    public ContainerResponseFilter getResponseFilter() {
        return null;
    }
}

我猜测差异与以下事实有关：MyFilter中的注入是使用遵循线程局部实例的代理完成的 – 这是因为用@Context注释的字段在外部类中声明,它被实例化一次,但它们用于按请求注入对象.当我在调试期间逐步执行过滤器时,我可以看到MyFilter.request指向包含com.sun.jersey.server.impl.container.servlet.ThreadLocalInvoker实例的代理.

什么是我的自定义提供程序(或其他实现)缺少它需要自定义注入我的过滤器？

请注意,我目前仍然坚持使用Jersey 1.1.4.1(对不起).

编辑：使用Jersey 1.17,我在启动时得到一个例外：

SEVERE: Missing dependency for field: private mypackage.MyObject mypackage.MyFilter.myObject

最佳答案 我找到了使用
JSR-311的
Providers可注射接口的解决方法.首先,我必须让我的提供者实现
ContextResolver：

@Provider
public final class MyProvider
extends AbstractHttpContextInjectable<MyObject>
implements InjectableProvider<Context, Type>, ContextResolver<MyObject> {

    ...

    @Override
    public MyObject getContext(Class<?> type) {
        //in reality, using the same logic as before
        return new MyObject();
    }
}

然后我将Providers实例注入到我的过滤器中.当调用filter时,我用它来查找MyObject的ContextResolver并动态检索它：

public final class MyFilter implements ResourceFilter {

    @Context private HttpServletRequest request;
    @Context private Providers providers;

    @Override
    public ContainerRequestFilter getRequestFilter() {
        return new ContainerRequestFilter() {
            @Override
            public ContainerRequest filter(ContainerRequest containerRequest) {

                final ContextResolver<MyObject> myObjectResolver =
                            providers.getContextResolver(MyObject.class, null);
                final MyObject myObject =
                            myObjectResolver.getContext(MyObject.class);

                System.out.println(request != null);  //true
                System.out.println(myObject != null); //true

                return containerRequest;
            }
        };
    }

    ...
}

信用证转到this answer,因为我对提供商不屑一顾.解决方案有效,但它不是一个漂亮的解决方案.我仍然想在任何地方注入MyObject并让它工作,就像HttpServletRequest一样 – 我想知道我的提供者缺少它需要实现的目的.

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