泽西：ContainerRequestFilter不获取上下文ServletRequest

Question

要查看此问题的完整代码，请参阅此github

https://github.com/mobiusinversion/web-application

我正在使用Jersey 2.15开发ContainerRequestFilter。这是一个嵌入式的Jetty应用程序，它被遮蔽到一个单独的罐子中。

在防波堤起动器（主类）中：

public static void main(String[] args) throws Exception {
    ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
    context.setContextPath("/");
    Server jettyServer = new Server(10005);
    jettyServer.setHandler(context);
    ServletHolder jerseyServlet = context.addServlet(ServletContainer.class, "/*");
    jerseyServlet.setInitOrder(0);
    jerseyServlet.setInitParameter(ServerProperties.PROVIDER_PACKAGES, ServletConstants.COMPONENT_SCAN_ROOT);

    try {
        System.out.println("Starting Jetty");
        jettyServer.start();
        System.out.println("Jetty Started");
        jettyServer.join();
    } catch (Exception e) {
        System.out.println("Could not start server");
        e.printStackTrace();
    } finally {
        jettyServer.destroy();
    }
}

我有一个通过提供程序包含的过滤器

@Provider
public class ExampleProvider implements DynamicFeature {

    @Override
    public void configure(ResourceInfo resourceInfo, FeatureContext featureContext) {
        ExampleFilter exampleFilter = new ExampleFilter();
        featureContext.register(exampleFilter);
    }
}

则在筛选器中：

public class ExampleFilter implements ContainerRequestFilter {

    private static final Logger logger = LoggerFactory.getLogger(ExampleFilter.class);

    @Context
    private HttpServletRequest servletRequest;

    @Override
    public void filter(ContainerRequestContext containerRequestContext) throws IOException {
        logger.info("IP ADDRESS " + servletRequest.getRemoteAddr());
        // ...
    }

}

Caused by: java.lang.NullPointerException: null
at com.example.filters.ExampleFilter.filter(ExampleFilter.java:29) 
at org.glassfish.jersey.server.ContainerFilteringStage.apply(ContainerFilteringStage.java:131) 
at org.glassfish.jersey.server.ContainerFilteringStage.apply(ContainerFilteringStage.java:67) 

    <properties>
        <jersey.version>2.15</jersey.version>
        <jetty.version>9.2.6.v20141205</jetty.version>
    </properties>

    <!-- Jersey -->
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet</artifactId>
        <version>${jersey.version}</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-json-jackson</artifactId>
        <version>${jersey.version}</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey</groupId>
        <artifactId>jersey-bom</artifactId>
        <version>${jersey.version}</version>
        <type>pom</type>
        <scope>compile</scope>
    </dependency>

    <!-- Jetty -->
    <dependency>
        <groupId>org.eclipse.jetty</groupId>
        <artifactId>jetty-server</artifactId>
        <version>${jetty.version}</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.jetty</groupId>
        <artifactId>jetty-servlet</artifactId>
        <version>${jetty.version}</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.jetty</groupId>
        <artifactId>jetty-servlets</artifactId>
        <version>${jetty.version}</version>
    </dependency>

Answer 1

错误在于您在ExampleRequestFilterProvider中手动创建了ExampleRequestLoggingFilter的实例。依赖项注入仅对容器本身创建和管理的实例起作用，例如ExampleRequestFilterProvider。这解释了为什么@context注入在手动创建的实例中似乎不起作用。

一个解决方案是将注入点移动到ExampleRequestFilterProvider，然后将其传递给ExampleRequestLoggingFilter的构造函数。

@Provider
public class ExampleRequestFilterProvider implements DynamicFeature {

    @Context
    private HttpServletRequest request;

    @Override
    public void configure(ResourceInfo resourceInfo, FeatureContext featureContext) {
        ExampleRequestLoggingFilter exampleRequestLoggingFilter = new ExampleRequestLoggingFilter(request);
        featureContext.register(exampleRequestLoggingFilter);
    }

}

我在这里测试了它（Git项目值得称赞！）这对我起作用了。

请注意，您在这里传递的不是实际的HttpServletRequest实例，而是一个容器托管代理，它在每个方法调用时进一步委托给实际的实例，因此在这里不需要担心完整性和线程安全性。