Jersey: How to Add Jackson to Servlet Holder

Question

I am creating an embedded Jetty webapp with Jersey. I do not know how to add Jackson for automatic JSON serde here:

    ServletHolder jerseyServlet = contex         


        

Answer 1

One way is to just wrap the ResourceConfig in an explicit construction of the ServletContainer, as seen here.

Tested with your example

public class RestServer {

    public static void main(String[] args) throws Exception {

        // Create JAX-RS application.
        final ResourceConfig application = new ResourceConfig()
                .packages("jersey.jetty.embedded")
                .register(JacksonFeature.class);

        ServletContextHandler context 
                 = new ServletContextHandler(ServletContextHandler.SESSIONS);
        context.setContextPath("/");
        Server jettyServer = new Server(9090);
        jettyServer.setHandler(context);
        ServletHolder jerseyServlet = new ServletHolder(new
                org.glassfish.jersey.servlet.ServletContainer(application));
        jerseyServlet.setInitOrder(0);

        context.addServlet(jerseyServlet, "/*");

        // ... removed property (init-param) to compile. 

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

You could also...

without changing anything else in your original post, just set the init param to scan the Jackson provider package

jerseyServlet.setInitParameter(ServerProperties.PROVIDER_PACKAGES,
        "com.fasterxml.jackson.jaxrs.json;"
      + "jersey.jetty.embedded"  // my package(s)
);

Note your attempted use of ResourceConfig seems a little redundant, as you are already configuring your classes in the the init param. You could alternatively get rid of adding each class explicitly and just scan entire packages as I have done.

You could also...

just use the Jackson provider classes you need. You can look in the jar, and you will see more than just the marshalling/unmarhalling provider (Jackson[JAXB]JsonProvider), like a ExceptionMappers. You may not like these mappers and wand to configure your own. In which case, like I said, just include the provider you need. For example

jerseyServlet.setInitParameter(ServerProperties.PROVIDER_CLASSNAMES,
      "com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider");

jerseyServlet.setInitParameter(ServerProperties.PROVIDER_PACKAGES, 
      "jersey.jetty.embedded"  // my package(s)
);

After further testing...

Not sure what version of Jersey, but I am using Jersey 2.15 (with jersey-media-json-jackson:2.15), and without any further configuration from just scanning my package for my resource classes, the Jackson feature is already enabled. This is part of the auto discoverable features. I believe this was enable as of 2.8 or 2.9 for the Jackson feature. So if you are using a later one, I don't think you need to explicitly configure anything, at least from what I've tested :-)

---

UPDATE

All of the above examples have been tested with the below Maven pom.xml

    4.0.0
    com.underdog.jersey
    jersey-jetty-embedded
    1.0-SNAPSHOT
    jar
    
        UTF-8
        1.7
        1.7
        2.15
        9.2.6.v20141205
    

    
        
            org.glassfish.jersey.containers
            jersey-container-servlet
        
        
            org.glassfish.jersey.media
            jersey-media-json-jackson
        
        
            org.eclipse.jetty
            jetty-server
            ${jetty.version}
        
        
            org.eclipse.jetty
            jetty-servlet
            ${jetty.version}
        
        
            org.eclipse.jetty
            jetty-servlets
            ${jetty.version}
        
    

        
        
            
                org.glassfish.jersey
                jersey-bom
                ${jersey.version}
                pom
                import
            
        
    

And resource class

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

@Path("/json")
public class JsonResource {

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response getJson() {
        Resource resource = new Resource();
        resource.hello = "world";
        return Response.ok(resource).build();
    }

    public static class Resource {
        public String hello;
    }
}

Using path

http://localhost:9090/json