Spring 3 JavaConfig Example

Since Spring 3, JavaConfig features are included in core Spring module, it allow developer to move bean definition and Spring configuration out of XML file into Java class. But, you are still allow to use the classic XML way to define beans and configuration, the JavaConfig is just another alternative solution. See the different between classic XML definition and JavaConfig to define a bean in Spring container. Spring XML file :

Equivalent configuration in JavaConfig :

package com.mkyong.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.mkyong.hello.HelloWorld;
import com.mkyong.hello.impl.HelloWorldImpl;

@Configuration
public class AppConfig {

 @Bean(name="helloBean")
 public HelloWorld helloWorld() {
     return new HelloWorldImpl();
 }

}

Spring JavaConfig Hello World Now, see a full Spring JavaConfig example. 1. Directory Structure spring-javaconfig-folder 2. Dependency Library To see JavaConfig(@Configuration), you need to include CGLIB library. See dependencies:

 
  org.springframework
  spring-core
  ${spring.version}
 

 
  org.springframework
  spring-context
  ${spring.version}
 

 
 
  cglib
  cglib
  2.2.2
 

3. Spring Bean a simple bean.

package com.mkyong.hello;

public interface HelloWorld {

 void printHelloWorld(String msg);

}

package com.mkyong.hello.impl;

import com.mkyong.hello.HelloWorld;

public class HelloWorldImpl implements HelloWorld {

 @Override
 public void printHelloWorld(String msg) {

  System.out.println("Hello : " + msg);
 }

}

4. JavaConfig Annotation Annotate with @Configuration to tell Spring that this is the core Spring configuration file, and define bean via @Bean.

package com.mkyong.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.mkyong.hello.HelloWorld;
import com.mkyong.hello.impl.HelloWorldImpl;

@Configuration
public class AppConfig {

 @Bean(name="helloBean")
 public HelloWorld helloWorld() {
 return new HelloWorldImpl();
 }

}

5. Run it Load your JavaConfig class with AnnotationConfigApplicationContext

package com.mkyong.core;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.mkyong.config.AppConfig;
import com.mkyong.hello.HelloWorld;

public class App {
 public static void main(String[] args) {

            ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
     HelloWorld obj = (HelloWorld) context.getBean("helloBean");

     obj.printHelloWorld("Spring3 Java Config");

 }
}

Output Hello : Spring3 Java Config