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

By mkyong | September 16, 2012 | Viewed : 86,399 times

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

Markup

	<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

Java

package com.mkyong.customer.dao;

import org.springframework.stereotype.Repository;

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

CustomerService.java

Java

package com.mkyong.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

Java

package com.mkyong.customer.dao;

import javax.inject.Named;

@Named
public class CustomerDAO
{

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

CustomerService.java

Java

package com.mkyong.customer.services;

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

import com.mkyong.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.

Spring-AutoScan.xml – Scan bean automatically

Markup

<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.mkyong.customer" />

</beans>

App.java – Run it

Java

package com.mkyong;

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

import com.mkyong.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

Bash

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

Download it – Spring-JSR330-Example.zip (27kb)

References