Question

我有一个注释@MagicAnnotation，它允许我将参数注入我的资源。实施如下：

@Target({ElementType.PARAMETER, ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface MagicAnnotation {
}

public class MagicResolver extends ParamInjectionResolver<MagicAnnotation> {
    public MagicResolver() {
        super(MagicProvider.class);
    }
}

public class MagicProvider extends AbstractValueFactoryProvider {
    @Inject
    public MagicProvider(final MultivaluedParameterExtractorProvider provider, final ServiceLocator locator) {
        super(provider, locator, Parameter.Source.UNKNOWN);
    }

    @Override
    protected Factory<?> createValueFactory(final Parameter parameter) {
        return new MagicFactory();
    }
}

public class MagicFactory extends AbstractContainerRequestValueFactory<String> {
    @Context
    private HttpServletRequest request;

    @Override
    public String provide() {
        return request.getParameter("value");
    }
}

在我的JAX-RS配置中，我将binder注册如下：

public class MagicBinder extends AbstractBinder {
    @Override
    protected void configure() {
        bind(MagicProvider.class).to(ValueFactoryProvider.class).in(Singleton.class);
        bind(MagicResolver.class).to(new TypeLiteral<InjectionResolver<MagicAnnotation>>() {
        }).in(Singleton.class);
    }
}

register(new MagicBinder());

这很有效。用法示例：

@Path("/magic")
public class SomeTest {
    @MagicAnnotation
    private String magic;

    @GET
    public Response test() {
        return Response.ok(magic).build();
    }
}

现在，我想在@MagicAnnotation内使用ContainerRequestFilter。我试着如下：

@Provider
public class MagicFilter implements ContainerRequestFilter {
    @MagicAnnotation
    private String magic;

    @Override
    public void filter(final ContainerRequestContext context) {
        if (!"secret".equals(magic)) {
            throw new NotFoundException();
        }
    }
}

这在初始化期间提供以下内容：

java.lang.IllegalStateException: Not inside a request scope

经过一些调试后，我发现在HttpServletRequest中注入MagicFactory是个问题。我猜HttpServletRequest是一个请求上下文类（每个HTTP请求都不同），HK2无法为该类创建代理。难道HttpServletRequest本身不是代理人吗？

我怎样才能解决这个问题？

Answer 1

难道HttpServletRequest本身已经是代理吗？

是的，但是因为你试图将魔术注释目标注入过滤器（这是在应用程序启动时实例化的单例），所以调用工厂的provide()方法，调用HttpServletRequest。而且因为在启动时没有请求，所以你得到的不是最新的范围＆＃34;错误。

最简单的解决方法是使用javax.inject.Provider懒惰地检索注入的对象。这样，在您通过调用Provider#get()请求对象之前，不会调用工厂。

@Provider
public class MagicFilter implements ContainerRequestFilter {
    @MagicAnnotation
    private Provider<String> magic;

    @Override
    public void filter(final ContainerRequestContext context) {
                           // Provider#get()
        if (!"secret".equals(magic.get())) {
            throw new NotFoundException();
        }
    }
}

更新

好的，所以上面的解决方案不会起作用。似乎即使使用Provider，仍然会调用工厂。

我们需要做的是将magic值设为代理。但是String不能被代理，所以我做了一个包装器。

public class MagicWrapper {
    private String value;

    /* need to proxy */
    public MagicWrapper() {   
    }

    public MagicWrapper(String value) {
        this.value = value;
    }

    public String get() {
        return this.value;
    }
}

现在进行一些重组。我们应该首先理解的是所需的组件。您当前用于参数注入的模式是Jersey源中用于处理@PathParam和@QueryParam等参数的参数注入的模式。

用作该基础结构一部分的类是您正在使用的AbstractValueFactoryProvider和ParamInjectionResolver。但是这些类只是泽西岛用来保持DRY的真正的辅助类，因为要注入许多不同类型的参数。但是这些类只是为处理这个用例而需要实现的主要合同的扩展，即ValueFactoryProvider和InjectResolver。因此，我们可以通过直接实施这些合同来重构我们的用例，而不是使用Jersey＆＃34; helper＆＃34;基础设施。这允许我们在需要的地方创建代理。

要为我们的MagicWrapper创建代理，我们只需在Factory中为其配置AbstractBinder作为代理

@Override
public void configure() {
    bindFactory(MagicWrapperFactory.class)
        .to(MagicWrapper.class)
        .proxy(true)
        .proxyForSameScope(false)
        .in(RequestScoped.class);
}

对proxy的调用使对象可以代理，对proxyForSameScope(false)的调用确保当它在请求范围内时，它是实际对象，而不是代理。在这里真的没什么区别。只有真正重要的是调用proxy()。

现在要处理自定义注释注入，我们需要一个InjectionResolver。这是它的工作。

public class MagicInjectionResolver implements InjectionResolver<MagicAnnotation> {

    @Inject @Named(InjectionResolver.SYSTEM_RESOLVER_NAME)
    private InjectionResolver<Inject> systemResolver;

    @Override
    public Object resolve(Injectee injectee, ServiceHandle<?> handle) {
        if (injectee.getRequiredType() == MagicWrapper.class) {
            return systemResolver.resolve(injectee, handle);
        }
        return null;
    }

    @Override
    public boolean isConstructorParameterIndicator() { return false; }

    @Override
    public boolean isMethodParameterIndicator() { return true; }
}

如上所述，您当前使用的ParamInjectionResolver只是InjectionResolver的一种实现，它更加简化，但在这种情况下无法使用。所以我们自己实现它。我们除了检查类型以外我们什么都不做，所以我们只处理MagicWrapper的注入。然后我们将工作委托给系统InjectionResolver。

现在我们需要Jersey用于方法参数注入的组件，即ValueFactoryProvider。

public class MagicValueFactoryProvider implements ValueFactoryProvider {

    @Inject
    private ServiceLocator locator;

    @Override
    public Factory<?> getValueFactory(Parameter parameter) {
        if (parameter.isAnnotationPresent((MagicAnnotation.class))) {
            final MagicWrapperFactory factory = new MagicWrapperFactory();
            locator.inject(factory);
            return factory;
        }
        return null;
    }

    @Override
    public PriorityType getPriority() {
        return Priority.NORMAL;
    }
}

我们刚刚回到工厂，就像你在AbstractValueFactoryProvider中所做的那样。唯一的区别是，我们需要明确地注入它，以便它获得HttpServletRequest。这与泽西在AbstractValueFactoryProvider中所做的一样。

就是这样。以下是使用Jersey Test Framework的完整示例。像任何其他JUnit测试一样运行它。

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.logging.Logger;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.container.ContainerResponseContext;
import javax.ws.rs.container.ContainerResponseFilter;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.Response;
import javax.ws.rs.ext.Provider;

import org.glassfish.hk2.api.Factory;
import org.glassfish.hk2.api.Injectee;
import org.glassfish.hk2.api.InjectionResolver;
import org.glassfish.hk2.api.ServiceHandle;
import org.glassfish.hk2.api.ServiceLocator;
import org.glassfish.hk2.api.TypeLiteral;
import org.glassfish.hk2.utilities.binding.AbstractBinder;
import org.glassfish.jersey.filter.LoggingFilter;
import org.glassfish.jersey.process.internal.RequestScoped;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.server.model.Parameter;
import org.glassfish.jersey.server.spi.internal.ValueFactoryProvider;
import org.glassfish.jersey.servlet.ServletContainer;
import org.glassfish.jersey.test.DeploymentContext;
import org.glassfish.jersey.test.JerseyTest;
import org.glassfish.jersey.test.ServletDeploymentContext;
import org.glassfish.jersey.test.grizzly.GrizzlyWebTestContainerFactory;
import org.glassfish.jersey.test.spi.TestContainerFactory;
import org.junit.Test;

import static junit.framework.Assert.assertEquals;

/**
 * See http://stackoverflow.com/q/39411704/2587435
 * 
 * Run like any other JUnit test. Only one require dependency
 * <dependency>
 *   <groupId>org.glassfish.jersey.test-framework.providers</groupId>
 *   <artifactId>jersey-test-framework-provider-grizzly2</artifactId>
 *   <version>${jersey2.version}</version>
 *   <scope>test</scope>
 * </dependency>
 *
 * @author Paul Samsotha
 */
public class InjectionTest extends JerseyTest {

    @Path("test")
    public static class TestResource {
        @GET
        public String get(@MagicAnnotation MagicWrapper magic) {
            return magic.get();
        }
    }

    @Provider
    public static class MagicFilter implements ContainerResponseFilter {

        @MagicAnnotation
        private MagicWrapper magic;

        @Override
        public void filter(ContainerRequestContext request, ContainerResponseContext response) {
            response.getHeaders().add("X-Magic-Header", magic.get());
        }
    }

    @Override
    public ResourceConfig configure() {
        return new ResourceConfig()
            .register(TestResource.class)
            .register(MagicFilter.class)
            .register(new LoggingFilter(Logger.getAnonymousLogger(), true))
            .register(new AbstractBinder() {
                @Override
                public void configure() {
                    bindFactory(MagicWrapperFactory.class)
                            .to(MagicWrapper.class)
                            .proxy(true)
                            .proxyForSameScope(false)
                            .in(RequestScoped.class);
                    bind(MagicInjectionResolver.class)
                            .to(new TypeLiteral<InjectionResolver<MagicAnnotation>>(){})
                            .in(Singleton.class);
                    bind(MagicValueFactoryProvider.class)
                            .to(ValueFactoryProvider.class)
                            .in(Singleton.class);
                }
            });
    }

    @Override
    public TestContainerFactory getTestContainerFactory() {
        return new GrizzlyWebTestContainerFactory();
    }

    @Override
    public DeploymentContext configureDeployment() {
        return ServletDeploymentContext.forServlet(new ServletContainer(configure())).build();
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.PARAMETER, ElementType.FIELD})
    public static @interface MagicAnnotation {
    }

    public static class MagicWrapper {
        private String value;

        /* need to proxy */
        public MagicWrapper() {   
        }

        public MagicWrapper(String value) {
            this.value = value;
        }

        public String get() {
            return this.value;
        }
    }

    public static class MagicWrapperFactory implements Factory<MagicWrapper> {
        @Context
        private HttpServletRequest request;

        @Override
        public MagicWrapper provide() {
            return new MagicWrapper(request.getParameter("value"));
        }

        @Override
        public void dispose(MagicWrapper magic) {}
    }

    public static class MagicValueFactoryProvider implements ValueFactoryProvider {

        @Inject
        private ServiceLocator locator;

        @Override
        public Factory<?> getValueFactory(Parameter parameter) {
            if (parameter.isAnnotationPresent((MagicAnnotation.class))) {
                final MagicWrapperFactory factory = new MagicWrapperFactory();
                locator.inject(factory);
                return factory;
            }
            return null;
        }

        @Override
        public PriorityType getPriority() {
            return Priority.NORMAL;
        }
    }

    public static class MagicInjectionResolver implements InjectionResolver<MagicAnnotation> {

        @Inject @Named(InjectionResolver.SYSTEM_RESOLVER_NAME)
        private InjectionResolver<Inject> systemResolver;

        @Override
        public Object resolve(Injectee injectee, ServiceHandle<?> handle) {
            if (injectee.getRequiredType() == MagicWrapper.class) {
                return systemResolver.resolve(injectee, handle);
            }
            return null;
        }

        @Override
        public boolean isConstructorParameterIndicator() { return false; }

        @Override
        public boolean isMethodParameterIndicator() { return true; }
    }

    @Test
    public void testInjectionsOk() {
        final Response response = target("test").queryParam("value", "HelloWorld")
                .request().get();
        assertEquals("HelloWorld", response.readEntity(String.class));
        assertEquals("HelloWorld", response.getHeaderString("X-Magic-Header"));
    }
}

另见：

有关InjectionResolver的详情，请参阅here和here
Injecting Request Scoped Objects into Singleton Scoped Object with HK2 and Jersey

Jersey / HK2 - 通过注释注入在ContainerRequestFilter中的HttpServletRequest注入

1 个答案:

更新