Apache Jersey + Tomcat + Eclipse + Maven with “echo” in XML/JSON (REST GET) in less than 30 min. with troubleshooting tips

Disclaimer:

Started with simple settings (with not even JUnit J.)

Pre-requisite:

1.       Jdk (tested with 1.8)

2.       Tomcat (tested with 8)

3.       Eclipse (tested with Mars)

Steps:

1.       Create a Maven project in Eclipse

Create a blank web-project with maven-archtype-web

2.       Add dependencies in Maven

a.       Add jersey-bundle

b.       Ensure java 1.8 is used (not 1.5 as the default is set)

Pom.xml:

      <dependencies>

            <dependency>

                  <groupId>com.sun.jersey</groupId>

                  <artifactId>jersey-bundle</artifactId>

                  <version>1.19</version>

            </dependency>

      </dependencies>

      <build>

            <finalName>pidev</finalName>

            <plugins>

                  <plugin>

                        <groupId>org.apache.maven.plugins</groupId>

                        <artifactId>maven-compiler-plugin</artifactId>

                        <version>3.1</version>

                        <configuration>

                              <source>1.8</source>

                              <target>1.8</target>

                        </configuration>

                  </plugin>

            </plugins>

      </build>

3.       Add Tomcat server library in Eclipse AND include in Order and Export

·         Build Path -> Configure Build Path -> Libraries -> Add Library -> Server Runtime -> Apache Tomcat 8.0

4.       Configure Jersey to listen for URI

       <servlet>

            <servlet-name>Jersey Web Application</servlet-name>

            <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>

            <init-param>

                  <param-name>com.sun.jersey.config.property.packages</param-name>

                  <param-value><your package></param-value>

            </init-param>

            <load-on-startup>1</load-on-startup>

      </servlet>

      <servlet-mapping>

            <servlet-name>Jersey Web Application</servlet-name>

            <url-pattern>/rest/*</url-pattern>

      </servlet-mapping>

(Note that if the url-pattern is /* then url to address doesn’t need “rest” in the URI J)

5.       Write code

 package <your package>;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.PathParam;

import javax.ws.rs.Produces;

@Path("/xmlapi")

public class XMLAPI {

      @GET

      @Produces("application/xml")

      public String echo() {

            return ("<xmlapi>default echo</xmlapi>");

      }

      @Path("{c}")

      @GET

      @Produces("application/xml")

      public String echo(@PathParam("c") String c) {

            return ("<xmlapi>"+c+"</xmlapi>");

      }

}

For json

 package <your package>;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.PathParam;

import javax.ws.rs.Produces;

@Path("/jsonapi")

public class JsonAPI {

      @GET

      @Produces("application/json")

      public String echo() {

            return "{\"message\": \"default echo\"}";

      }

      @Path("{c}")

      @GET

      @Produces("application/xml")

      public String echo(@PathParam("c") String c) {

            return "{\"message\": \"" + c + "\"}";

      }

     

}

6.       Build and deploy

·         Maven -> Update project

·         Run project in Apache Tomcat

7.       Access the service

a.       Default (http://localhost:8080/<display-name>/rest/xmlapi)

Output:

<?xml version="1.0"?>

<xmlapi>default echo</xmlapi>

b.       With a message (http://localhost:8080/<display-name>/rest/xmlapi/hi)

Output:

<?xml version="1.0"?>

<xmlapi>hi</xmlapi>

Potential problems:

1.       Project don’t compile:

Java compiler level does not match the version of the installed Java project facet.

JAX-RS (REST Web Services) 2.0 requires Java 1.6 or newer.

One or more constraints have not been satisfied.

Maven default uses 1.5 J

Solution:

Add/update build element of pom.xml

      <build>

            <finalName><Project name></finalName>

            <plugins>

                  <plugin>

                        <groupId>org.apache.maven.plugins</groupId>

                        <artifactId>maven-compiler-plugin</artifactId>

                        <version>3.1</version>

                        <configuration>

                              <source>1.8</source>

                              <target>1.8</target>

                        </configuration>

                  </plugin>

            </plugins>

      </build>

2.       Jersey didn’t load your mapping

com.sun.jersey.api.core.ScanningResourceConfig.init No provider classes found.

Solution:

In web.xml ensure that correct package is specified in init-param

      <servlet>

            <servlet-name>Jersey Web Application</servlet-name>

            <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>

            <init-param>

                  <param-name>com.sun.jersey.config.property.packages</param-name>

                  <param-value><your package></param-value>

            </init-param>

            <load-on-startup>1</load-on-startup>

      </servlet>

3.       Status 500 UriBuilder

Duplicate UriBuilder J Usually it happens if you try different dependencies and one of those dependencies downloads it for you (e.g. jersey-bundle with jersey-server or jersey-apache-connector)

Solution:

Remove javax.ws.rs-api.jar.