Spring中使用两种Aware接口自定义获取bean

　　在使用spring编程时，常常会遇到想根据bean的名称来获取相应的bean对象，这时候，就可以通过实现BeanFactoryAware来满足需求，代码很简单：

@Service
public class BeanFactoryHelper implements BeanFactoryAware {
    
    private static BeanFactory beanFactory;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }
    
    public static Object getBean(String beanName){

　　　　 if(beanFactory == null){
            throw new NullPointerException("BeanFactory is null!");
        }

　　　　 return beanFactory.getBean(beanName); 
　　} 
}

　　还有一种方式是实现ApplicationContextAware接口，代码也很简单：

@Service
public class ApplicationContextHelper implements ApplicationContextAware {
    
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
    
    public static Object getBean(String beanName){
        if(applicationContext == null){
            throw new NullPointerException("ApplicationContext is null!");
        }
        return applicationContext.getBean(beanName);
    }

}

　　上面两种方法，只有容器启动的时候，才会把BeanFactory和ApplicationContext注入到自定义的helper类中，如果在本地junit测试的时候，如果需要根据bean的名称获取bean对象，则可以通过ClassPathXmlApplicationContext来获取一个ApplicationContext，代码如下：

　　@Test
    public void test() throws SQLException {
        //通过从classpath中加载spring-mybatis.xml实现bean的获取
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-mybatis.xml");
        IUserService userService = (IUserService) context.getBean("userService");

        User user = new User();
        user.setName("test");
        user.setAge(20);
        userService.addUser(user);
    }