Spring ApplicationContextAware获取上下文

一、ApplicationContextAware 用处

　　Spring 提供了ApplicationContextAware类，通过它可以获取所有bean上下文。

二、怎么用？

　　①、定义一个工具类，去实现 ApplicationContextAware，实现 setApplicationContext方法即可

public class SpringContextUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext; // Spring应用上下文环境

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContextUtil.applicationContext = applicationContext;
    }

    /**
     * 获取对象
     * 
     * @param name
     * @return Object 一个以所给名字注册的bean的实例
     * @throws BeansException
     */
    public static Object getBean(String name) throws BeansException {
        return applicationContext.getBean(name);
    }

}

　　②、业务代码

public interface UserReadService {

    public UserInfo getUserInfoById(Long id);
}

@Component("userReadService")
public class UserReadServiceImpl implements UserReadService {

    @Override
    public UserInfo getUserInfoById(Long id) {
        System.out.println("获取用户信息");
        return null;
    }

}

　　③、xml 配置

<?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-4.1.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-4.1.xsd">


    <context:annotation-config />
    <!--自动扫描含有@Service将其注入为bean -->
    <context:component-scan base-package="com.mycompany.yuanmeng.springdemo.aop" />

    <bean id="springContextUtil" class="com.mycompany.yuanmeng.springdemo.aop.SpringContextUtil" />

</beans>

　　④、test

public static void test() {
        
        new ClassPathXmlApplicationContext("spring.xml"); // 加载ApplicationContext（模拟启动web服务）, 当然如果是用web工程的话,可以直接在web.xml配置，容器会去加载此文件。
        
        UserReadService userReadService = (UserReadService) SpringContextUtil.getBean("userReadService");
        
        userReadService.getUserInfoById(null);
 }