spring依赖注入(Ioc)控制反转

控制反转（英语：Inversion of control，缩写为IoC），也叫做依赖注入（Dependency Injection，简称DI），是面向对象编程中的一种设计原则，可以用来减低计算机代码之间的耦合度。

在面向对象开发过程中，类与类的关系可能非常复杂。而类与类之间的关系或依赖，导致系统的紧密耦合。

而依赖注入是解决对象间的紧密耦合，将原来在类内部控制的依赖交给系统去控制。

下面是基于注解的注入案例

配置文件spring.xml

<?xml version="1.0" encoding="UTF-8"?><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-2.5.xsd           http://www.springframework.org/schema/context           http://www.springframework.org/schema/context/spring-context-2.5.xsd">     <context:component-scan base-package="spring.test"/></beans>

主业务类PersonService.java

package spring.test;import javax.annotation.PostConstruct;import javax.annotation.PreDestroy;import javax.annotation.Resource;import org.springframework.context.annotation.Scope;import org.springframework.stereotype.Service;/** * @function :  * @author   :jy * @company  :万里网 * @date     :2011-10-12 */@Service("person")@Scope("prototype")public class PersonService {private InfoDao info;private String username;private int age;@Resource(name="baseInfo") public void setInfo(InfoDao info){this.info = info;}public PersonService(){}@PostConstructpublic void init(){System.out.println("初始化完成");}@PreDestroypublic void destory(){System.out.println("注销完成");}public PersonService(String username, int age){this.username = username;this.age   = age;}@Overridepublic String toString() {return "Person [username=" + username + ", age=" + age + "]";}public void printInfo(){System.out.println(info);}}

数据访问组件InfoDao.java

package spring.test;import org.springframework.stereotype.Repository;/** * @function :  * @author   :jy * @company  :万里网 * @date     :2011-10-12 */@Repository("baseInfo")public class InfoDao {/* (non-Javadoc) * @see java.lang.Object#toString() */@Overridepublic String toString() {return "User BaseInfo";}}

JUnit测试文件

package spring.test;import org.junit.BeforeClass;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;/** * @function :  * @author   :jy * @company  :万里网 * @date     :2011-10-12 */public class TestSpring {/** * @throws java.lang.Exception */@BeforeClasspublic static void setUpBeforeClass() throws Exception {}@Test public void instanceBean(){ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");PersonService person = (PersonService) ctx.getBean("person");person.printInfo();}}