JAX-RS - Injecting Servlet Resources With @Context annotation

The @Context annotation can be used to inject a Servlet-managed resources: ServletConfig, ServletContext, HttpServletRequest and HttpServletResponse.

Example

@Path("/")
public class ExampleResource {
    @Context
    private ServletConfig servletConfig;
    @Context
    private ServletContext servletContext;
    @Context
    private HttpServletRequest httpServletRequest;
    @Context
    private HttpServletResponse httpServletResponse;

    @GET
    @Path("/test")
    public void handleRequest() throws IOException {
        System.out.println("-- in resource method --");
        printServletConfigInfo();
        printServletContextInfo();
        printServletRequestInfo();
        //committing response using HttpServletResponse
        httpServletResponse.getWriter().write("Test response");
        httpServletResponse.getWriter().flush();
    }

    private void printServletRequestInfo() {
        System.out.println("-- Servlet Request --");
        System.out.println("Request URI: " + httpServletRequest.getRequestURI());
        Enumeration<String> headerNames = httpServletRequest.getHeaderNames();
        ArrayList<String> list = Collections.list(headerNames);
        System.out.println("Request headers: " + list.size());
        list.forEach(h -> System.out.println(h + " = " + httpServletRequest.getHeader(h)));
    }

    private void printServletContextInfo() {
        System.out.println("-- Servlet Context --");
        System.out.println("Context path: " + servletContext.getContextPath());
        System.out.println("Server info: " + servletContext.getServerInfo());
        Enumeration<String> attributeNames = servletContext.getAttributeNames();
        ArrayList<String> list = Collections.list(attributeNames);
        System.out.println("Context attributes: " + list.size());
        System.out.println("Session Tracking modes: " + servletContext.getDefaultSessionTrackingModes());
    }

    private void printServletConfigInfo() {
        System.out.println("-- Servlet Config Params --");
        Enumeration<String> initParameterNames = servletConfig.getInitParameterNames();
        ArrayList<String> list = Collections.list(initParameterNames);
        System.out.println("Init params: " + list.size());
        list.forEach(n -> System.out.println(n + " = " + servletConfig.getInitParameter(n)));
        System.out.println("Servlet name: " + servletConfig.getServletName());
    }
}

mvn tomcat7:run-war

The JAX-RS client

public class ExampleClient {
    public static void main(String[] args) {
        Client client = ClientBuilder.newClient();
        WebTarget target =
                client.target("http://localhost:8080/test");
        Response response = target.request()
                                  .get();
        System.out.printf("status: %s%n", response.getStatus());
        System.out.printf("-- response body --%n%s%n", response.readEntity(String.class));
    }
}

status: 200
-- response body --
Test response

Output On Server

-- in resource method --
-- Servlet Config Params --
Init params: 0
Servlet name: com.logicbig.example.MyApp
-- Servlet Context --
Context path:
Server info: Apache Tomcat/7.0.47
Context attributes: 9
Session Tracking modes: [COOKIE, URL]
-- Servlet Request --
Request URI: /test
Request headers: 4
user-agent = Jersey/2.25.1 (HttpUrlConnection 1.8.0_65)
host = localhost:8080
accept = text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
connection = keep-alive

Example Project

Dependencies and Technologies Used:

• jersey-server 2.25.1: Jersey core server implementation.
• jersey-container-servlet 2.25.1: Jersey core Servlet 3.x implementation.
• javax.servlet-api 3.0.1 Java Servlet API
• JDK 1.8
• Maven 3.3.9