What is best approach for implementing Jersey 2.x on Tomcat 8?

Question

I have Knowledge of the Web container and Tomcat and can deploy static and dynamic web sites. But I am new to REST and Jersey. I have read the 2.6 user's guide, reviewed many sites and youtube videos. There seems to be a lot of info on 1.x Jersey but not much on 2.x I can get 1.18 working in my environment but can't seem to get any deployment models working for 2.x. I noticed in 2.x there is an Application deployment model. So I thought i would ask some very generic questions to get this started.

1. Which deployment model is best for basic REST services through Tomcat 8 and why?
2. I see that the .jars deployed with 2.6 are much different than the ones deployed with 1.18. Is there an easy way to tell which jars you need for a basic Tomcat installation?
3. If you have a basic example, that would be great.

Thanks

Answer 1

What follows are what I hope are relatively complete solutions to your questions.

You don't mention Maven, so I will: Maven is your friend here.

Let's start with a pom:

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example.groupid</groupId>
  <artifactId>stack</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>org.glassfish.jersey.containers</groupId>
      <artifactId>jersey-container-servlet-core</artifactId>
      <version>2.13</version>
    </dependency>
    <dependency>
      <groupId>org.glassfish.jersey.containers</groupId>
      <artifactId>jersey-container-servlet</artifactId>
      <version>2.13</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>stack</finalName>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-war-plugin</artifactId>
        <version>2.5</version>
      </plugin>

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.2</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
    </plugins>
  </build>
  <name>Stack</name>
</project>

That might not be the absolute minimum in terms of dependencies, but it's close.

But that's just the pom. The trickery continues in the web.xml and the Java classes.

About that web.xml...

It's insanely complicated, so bear with me:

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         metadata-complete="false"
         version="3.1">
</web-app>

Ok, maybe not that complicated.

Note that setting metadata-complete="true" may result in Tomcat starting faster.

A pair of Java classes

One is the "application", the other is the rest call.***

The rest call is pretty straightforward:

package some.package;

import javax.ws.rs.GET;
import javax.ws.rs.Path;

@Path("/hello")
public class HelloRest {

  @GET
  public String message() {
    return "Hello, rest!";
  }
}

The application looks like this:

package some.package;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;

import some.package.HelloRest;

@ApplicationPath("/rest")
public class RestApp extends Application {
  public Set<Class<?>> getClasses() {
    return new HashSet<Class<?>>(Arrays.asList(HelloRest.class));
  }
}

And that's it. When you navigate to something like http://localhost:8080/stack/rest/hello, you should see the text "Hello, rest!"

Leverage Jersey a bit.

getClasses() in RestApp is a little ugly. You might use Jersey's ResourceConfig, as at the Jersey User's Guide, which would look like this:

public class RestApp extends ResourceConfig {
    public RestApp() {
        packages("some.package");
    }
}

But I don't want to use Maven!

Fine. These are the jars Eclipse lists as Maven dependencies:

• javax.servlet-api-3.1.0.jar
• jersey-container-servlet-core-2.13.jar
• javax.inject-2.3.0-b10.jar
• jersey-common-2.13.jar
• javax.annotation-api-1.2.jar
• jersey-guava-2.13.jar
• hk2-api-2.3.0-b10.jar
• hk2-utils-2.3.0-b10.jar
• aopalliance-repackaged-2.3.0-b10.jar
• hk2-locator-2.3.0-b10.jar
• javassist-3.18.1-GA.jar
• osgi-resource-locator-1.0.1.jar
• jersey-server-2.13.jar
• jersey-client-2.13.jar
• validation-api-1.1.0.Final.jar
• javax.ws.rs-api-2.0.1.jar
• jersey-container-servlet-2.13.jar

Presumably, adding those manually to your classpath should work. Or use Maven.

Answer 2

I was able to get this working using the directions supplied in the Jersey 2.6 user's guide for deployment to a 3.x servlet container. I ended up using something similar to the item below. Because the URL mapping is supplied in the .xml, you can omit @ApplicationPath from the Application subclass.

<web-app version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

    <!-- Servlet declaration can be omitted in which case
         it would be automatically added by Jersey -->
    <servlet>
        <servlet-name>org.example.MyApplication</servlet-name>
    </servlet>

    <!-- Servlet mapping can be omitted in case the Application subclass
         is annotated with @ApplicationPath annotation; in such case
         the mapping would be automatically added by Jersey -->
    <servlet-mapping>
        <servlet-name>org.example.MyApplication</servlet-name>
        <url-pattern>/myresources/*</url-pattern>
    </servlet-mapping>
</web-app>