Jersey: ContainerRequestFilter does not get Contex

Question

To see the full code for this issue, please see this github

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

I also created this Jersey Jira

https://java.net/jira/browse/JERSEY-2851

I am working on a ContainerRequestFilter using Jersey 2.15. This is an embedded Jetty app which is shaded into a single jar.

In the Jetty starter (main class):

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();
    }
}

I have a filter which is included via a provider

@Provider
public class ExampleProvider implements DynamicFeature {

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

Then in the filter:

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());
        // ...
    }

}

However this produces a NullPointerException:

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) 

What am I doing wrong and how do I fix this?

UPDATE: Including pom entried for Jetty and Jersey

    <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

The mistake was that you manually created an instance of ExampleRequestLoggingFilter inside the ExampleRequestFilterProvider. Dependency injection only works on instances created and managed by the container itself, such as the ExampleRequestFilterProvider. This explains why @Context injection didn't seem to work in your manually created instance.

A solution would be to move the injection point to the ExampleRequestFilterProvider and then pass it through to the constructor of ExampleRequestLoggingFilter.

@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);
    }

}

I tested it here (kudos to the Git project!) and it worked for me.

Note that you're here not passing the actual HttpServletRequest instance, but a container managed proxy which delegates further to the actual instance on every method call, so there's nothing to worry as to integrity and threadsafety here.