Spring中使用兩種Aware接口自定義獲取bean

　　在使用spring編程時，常常會遇到想根據bean的名稱來獲取相應的bean對象，這時候，就可以通過實現BeanFactoryAware來滿足需求，代碼很簡單：

@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); 
　　} 
}

　　還有一種方式是實現ApplicationContextAware接口，代碼也很簡單：

@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);
    }

}

　　上面兩種方法，只有容器啟動的時候，才會把BeanFactory和ApplicationContext注入到自定義的helper類中，如果在本地junit測試的時候，如果需要根據bean的名稱獲取bean對象，則可以通過ClassPathXmlApplicationContext來獲取一個ApplicationContext，代碼如下：

　　@Test
    public void test() throws SQLException {
        //通過從classpath中加載spring-mybatis.xml實現bean的獲取
        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);
    }