Jersey: How to Add Jackson to Servlet Holder
I am creating an embedded Jetty webapp with Jersey. I do not know how to add Jackson for automatic JSON serde here:
ServletHolder jerseyServlet = context.addServlet(
org.glassfish.jersey.servlet.ServletContainer.class, "/*");
jerseyServlet.setInitOrder(0);
jerseyServlet.setInitParameter(
ServerProperties.PROVIDER_CLASSNAMES,
StringUtils.join(
Arrays.asList(
HealthCheck.class.getCanonicalName(),
Rest.class.getCanonicalName()),
";"));
// Create JAX-RS application.
final Application application = new ResourceConfig()
.packages("com.example.application")
.register(JacksonFeature.class);
// what do I do now to tie this to the ServletHolder?
How do I register this ResourceConfig with the ServletHolder so Jackson with be used where the annotation @Produces(MediaType.APPLICATION_JSON) is used? Here is the full main class for the embedded Jetty application
package com.example.application.web;
import com.example.application.api.HealthCheck;
import com.example.application.api.Rest;
import com.example.application.api.Frontend;
import org.apache.commons.lang.StringUtils;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;
import org.glassfish.jersey.jackson.JacksonFeature;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.server.ServerProperties;
import javax.ws.rs.core.Application;
import java.util.Arrays;
public class JettyStarter {
public static void main(String[] args) throws Exception {
ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
context.setContextPath("/");
Server jettyServer = new Server(9090);
jettyServer.setHandler(context);
ServletHolder jerseyServlet = context.addServlet(
org.glassfish.jersey.servlet.ServletContainer.class, "/*");
jerseyServlet.setInitOrder(0);
jerseyServlet.setInitParameter(
ServerProperties.PROVIDER_CLASSNAMES,
StringUtils.join(
Arrays.asList(
HealthCheck.class.getCanonicalName(),
Rest.class.getCanonicalName()),
";"));
// Create JAX-RS application.
final Application application = new ResourceConfig()
.packages("com.example.application")
.register(JacksonFeature.class);
try {
jettyServer.start();
jettyServer.join();
} catch (Exception e) {
System.out.println("Could not start server");
e.printStackTrace();
} finally {
jettyServer.destroy();
}
}
}
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
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.underdog.jersey</groupId>
<artifactId>jersey-jetty-embedded</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
<jersey.version>2.15</jersey.version>
<jetty.version>9.2.6.v20141205</jetty.version>
</properties>
<dependencies>
<dependency>
<groupId>org.glassfish.jersey.containers</groupId>
<artifactId>jersey-container-servlet</artifactId>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-jackson</artifactId>
</dependency>
<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>${jetty.version}</version>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.glassfish.jersey</groupId>
<artifactId>jersey-bom</artifactId>
<version>${jersey.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>
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