Dependency Injection with HK2 in Jersey and JAX-RS

Adding dependency injection support into Jersey 2 Web Services application that uses HK2 is not very straightforward. So, I created this page to document things I needed to do in my Jersey 2 RESTful Web Services app to make the Dependency Injection work. Hope you will find it useful.

Create a new class that extends AbstractBinder. This class will need to bind classes that participate in Dependency Injection.

package com.appsdeveloperblog.app.ws;

import com.appsdeveloperblog.app.ws.service.UserService;
import com.appsdeveloperblog.app.ws.service.impl.UserServiceImpl;
import com.appsdeveloperblog.com.app.ws.io.repositories.UserRepository;
import org.glassfish.hk2.utilities.binding.AbstractBinder;

/**
 *
 * @author skargopolov
 */
public class MyApplicationBinder extends AbstractBinder {
    @Override
    protected void configure() {
        bind(UserServiceImpl.class).to(UserService.class);
        bind(UserRepository.class).to(UserRepository.class);
    }
}

Create a new class that extends ResourceConfig. This class will be used to register a class that extends AbstractBinder. An example of this class is above and in my case, it is called MyApplicationBinder.

package com.appsdeveloperblog.app.ws;
 
import org.glassfish.jersey.server.ResourceConfig;

/**
 *
 * @author skargopolov
 */
public class App extends ResourceConfig{
    public App() {
       packages("com.appsdeveloperblog.app.ws");
       register(new MyApplicationBinder());  
    }
}

Updated Root Resouce class to Inject the service. Notice the @Inject annotation above the UserService. This annotation is required for UserService class to be injected into this Root Resource class.

@Path("users")
public class Users {
    
    public Users(){}
    
    @Inject
    UserService userService;
     
    @POST
    @Consumes({ MediaType.APPLICATION_JSON,  MediaType.APPLICATION_XML} )
    @Produces({ MediaType.APPLICATION_JSON,  MediaType.APPLICATION_XML} )
    public UserProfileRest createUser(CreateUserModelRest createUserModel) {
        UserProfileRest returnValue = new UserProfileRest();
        UserProfileDto userDto = new UserProfileDto();
      
        BeanUtils.copyProperties(createUserModel, userDto);
        
        UserProfileDto createdUserDto = userService.createUser(userDto);
        
        BeanUtils.copyProperties(createdUserDto, returnValue);
        
        return returnValue;
    }

}

If you want to use BeanUtils as in my code above then add the below dependency to your pom.xml file:

<!-- https://mvnrepository.com/artifact/org.springframework/spring-beans -->
 <dependency>
     <groupId>org.springframework</groupId>
     <artifactId>spring-beans</artifactId>
     <version>4.3.7.RELEASE</version>
 </dependency>

Update Service layer classes. If you would like your Service layer class to also use Dependency Injection update then use Constructor-based dependency injection as shown below. Do not forget to bind this class in a MyApplicationBinder as shows in the MyApplicationBinder class above.

package com.appsdeveloperblog.app.ws.service.impl;

import com.appsdeveloperblog.app.ws.service.UserService;
import com.appsdeveloperblog.app.ws.shared.dto.UserProfileDto;
import com.appsdeveloperblog.com.app.ws.io.repositories.UserRepository;
import java.util.List;
import javax.inject.Inject;

/**
 *
 * @author skargopolov
 */
public class UserServiceImpl implements UserService {
    
    UserRepository userRepository;
    
    @Inject
    public UserServiceImpl(UserRepository userRepository)
    {
        this.userRepository = userRepository;
    }

    @Override
    public UserProfileDto createUser(UserProfileDto user) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

Update your web.xml file which is in WEB-INF folder. If your web.xml file does not have the two init-param which are below, then add them. The first init-param’s value is the root package name which contains your JAX-RS resources. And the second init-param value is the complete package name of your App.java file. Please note that it is a package name + class name.

<init-param>
     <param-name>jersey.config.server.provider.packages</param-name>
     <param-value>com.appsdeveloperblog.app.ws</param-value>
 </init-param>
 <init-param>
     <param-name>javax.ws.rs.Application</param-name>
      <param-value>com.appsdeveloperblog.app.ws.App</param-value>
 </init-param>

Below is my complete web.xml file which contains these two init params:

<?xml version="1.0" encoding="UTF-8"?>
<!-- This web.xml file is not required when using Servlet 3.0 container,
     see implementation details http://jersey.java.net/nonav/documentation/latest/jax-rs.html -->
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <servlet>
        <servlet-name>Jersey Web Application</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>com.appsdeveloperblog.app.ws</param-value>
        </init-param>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
             <param-value>com.appsdeveloperblog.app.ws.App</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
 
    <servlet-mapping>
        <servlet-name>Jersey Web Application</servlet-name>
        <url-pattern>/webapi/*</url-pattern>
    </servlet-mapping>
</web-app>

How would it change your life if you knew how to build RESTful Web Services with Jersey and JAX-RS very well? I know from my personal experience that learning on the internet by reading programming tutorial is not the fastest way to progress. Below is a list of step by step video courses that might help you learn most of the things you need about Jersey and JAX-RS and feel much more confident as a RESTful Web Services developer!

Dependency Injection with HK2 in Jersey and JAX-RS

Learning RESTful Web Services Development

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