注解@AutoWired

Spring的注解@AutoWired主要是对类的成员变量进行自动装配工作。

例如有两个实体Subs和SubsOper，SubsOper存放Subs的具体业务方法，将SubsOper作为Subs的成员变量存在。

SubsOper.java

public class SubsOper {
    public SubsOper() {
        System.out.println("this is the SubsOper constructor...");
    }
    
    public void changePsw() {
        System.out.println(this.name+" begin to change password...");
    }
}

Subs.java

public class Subs {
    @Autowired
    private SubsOper subsOper;
    
    public void changePsw() {
        subsOper.changePsw();
    }
}

bean.xml  配置文件配置如下，注意红色标注的部分，这个是必须的，否则@AutoWired不会生效。

<?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-3.0.xsd
		   http://www.springframework.org/schema/context
		   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
		   
        <span style="color:#ff0000;"><context:annotation-config/></span>
    
	<bean id="Subs" class="com.dicover.Subs"/>
	<bean id="SubsOper" class="com.dicover.SubsOper"/>
</beans>

写一个测试类AutoWiredTest.java来看看执行的结果

public class AutoWiredTest {

    /**
     * Description: <br> 
     */
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
        Subs subs = context.getBean("Subs", Subs.class);
        subs.changePsw();
    }

}

执行结果：

log4j:WARN No appenders could be found for logger (org.springframework.context.support.ClassPathXmlApplicationContext).
log4j:WARN Please initialize the log4j system properly.
this is the SubsOper constructor...
 begin to change password...

this is the SubsOper constructor打印出来表明subsOper对象自动初始化成功，否则如果没有用@AutoWired就会报空指针异常，begin to change password打印出来表明能够调用到SubsOper中的方法。