Spring 3 and JSR-330 @Inject and @Named example

Since Spring 3.0, Spring supports for the standard JSR 330: Dependency Injection for Java. In Spring 3 application, you can uses standard

1. @Inject instead of Spring’s @Autowired to inject a bean.
2. @Named instead of Spring’s @Component to declare a bean.

Those JSR-330 standard annotations are scanned and retrieved the same way as Spring annotations, the integration just happened automatically, as long as the following jar in your classpath.

pom.xml

	<dependency>
		<groupId>javax.inject</groupId>
		<artifactId>javax.inject</artifactId>
		<version>1</version>
	</dependency>

1. Spring Annotations

Let see a normal Spring’s annotation example – @Autowired and @Component

P.S @Component, @Repository and @Service are same, just declares a bean in Spring Ioc context.

CustomerDAO.java

package com.favtuts.customer.dao;

import org.springframework.stereotype.Repository;

@Repository
public class CustomerDAO 
{
	public void save() {
		System.out.println("CustomerDAO save method...");
	}	
}

CustomerService.java

package com.favtuts.customer.services;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.mkyong.customer.dao.CustomerDAO;

@Service
public class CustomerService 
{
	@Autowired
	CustomerDAO customerDAO;

	public void save() {
		
		System.out.println("CustomerService save method...");
		customerDAO.save();
		
	}
		
}

2. JSR-330 Annotations

Basically, it works the same, just with different annotations – @Inject and @Named.

CustomerDAO.java

package com.favtuts.customer.dao;

import javax.inject.Named;

@Named
public class CustomerDAO 
{
	
	public void save() {
		System.out.println("CustomerDAO save method...");
	}	
}

CustomerService.java

package com.favtuts.customer.services;

import javax.inject.Inject;
import javax.inject.Named;

import com.favtuts.customer.dao.CustomerDAO;

@Named
public class CustomerService 
{
	@Inject
	CustomerDAO customerDAO;

	public void save() {
		
		System.out.println("CustomerService save method...");
		customerDAO.save();
		
	}
		
}

3. Run it

Both Spring and JSR330 annotations need component scan to works.

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.1.xsd">

    <context:component-scan base-package="com.favtuts.customer" />
 
</beans>

App.java – Run it

package com.favtuts;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.favtuts.customer.services.CustomerService;

public class App 
{
    public static void main( String[] args )
    {
    	ApplicationContext context = 
    		new ClassPathXmlApplicationContext(new String[] {"Spring-AutoScan.xml"});

    	CustomerService cust = (CustomerService)context.getBean("customerService");
    	cust.save();
    	
    }
}

Above two examples are generated the same output

CustomerService save method...
CustomerDAO save method...

4. JSR-330 Limitations

There are some limitations on JSR-330 if compare to Spring :

1. @Inject has no “required” attribute to make sure the bean is injected successful.
2. In Spring container, JSR-330 has scope singleton by default, but you can use Spring’s @Scope to define others.
3. No equivalent to Spring’s @Value, @Required or @Lazy.

Check out this Spring references.

5. Go for JSR-330

In fact, Spring’s annotations are more powerful, but only available on Spring framework. The JSR-330 is a standard spec, and it’s supported on all J2ee environment that follow the JSR-330 spec.

For new or migration project, it’s always recommended to use JSR-330 annotations, and remember, it works on Spring 3 as well.

Download Source Code

$ git clone https://github.com/favtuts/java-spring-tutorials.git
$ cd Spring-JSR330-Example

References

1. Spring Reference : Using JSR 330 Standard Annotations
2. JSR 330: Dependency Injection for Java
3. Spring DI via setter method
4. Spring DI via constructor
5. Spring @PropertySource example
6. Spring Tutorial