<?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:annotation-config/>

  <bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl">

  </bean>

  <bean id="u2" class="com.bjsxt.dao.impl.UserDAOImpl">

  </bean>

   <bean id="userService" class="com.bjsxt.service.UserService">

  </bean>

</beans>

package com.bjsxt.service;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.beans.factory.annotation.Qualifier;

import com.bjsxt.dao.UserDAO;

import com.bjsxt.model.User;

public class UserService {

    private UserDAO userDAO;

    public void add(User user) {

        userDAO.save(user);

    }

    public UserDAO getUserDAO() {

        return userDAO;

    }

    //为什么Autowired必须放在set里面，其他地方无效

    @Autowired

    public void setUserDAO(@Qualifier("u")UserDAO userDAO) {

        this.userDAO = userDAO;

    }

    public void init(){

        System.out.println("init");

    }

    public void destroy(){

        System.out.println("destroy");

    }

}

    @Test

    public void test() {

        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");

        UserService service = (UserService)ctx.getBean("userService");

        service.add(new User());

        ctx.destroy();

疑问：为什么autowired必须放在set方法里面在测试之中？

Annotation-based configuration

(The implicitly registered post-processors include AutowiredAnnotationBeanPostProcessor, CommonAnnotationBeanPostProcessor, PersistenceAnnotationBeanPostProcessor, as well as the aforementioned RequiredAnnotationBeanPostProcessor.)

Note that <context:annotation-config/> only looks for annotations on beans in the same application context it is defined in. This means that, if you put <context:annotation-config/> in a WebApplicationContext for a DispatcherServlet, it only checks for @Autowired beans in your controllers, and not your services. See Section 13.2, “The DispatcherServlet” for more information.

As expected, the @Autowired annotation may be applied to "traditional" setter methods:

public class SimpleMovieLister {

    private MovieFinder movieFinder;

    @Autowired

    public void setMovieFinder(MovieFinder movieFinder) {

        this.movieFinder = movieFinder;

    }

    // ...

}

The annotation may also be applied to methods with arbitrary names and/or multiple arguments:

public class MovieRecommender {

    private MovieCatalog movieCatalog;

    private CustomerPreferenceDao customerPreferenceDao;

    @Autowired

    public void prepare(MovieCatalog movieCatalog, CustomerPreferenceDao customerPreferenceDao) {

        this.movieCatalog = movieCatalog;

        this.customerPreferenceDao = customerPreferenceDao;

    }

    // ...

}

The @Autowired annotation may even be applied on constructors and fields:

public class MovieRecommender {

    @Autowired

    private MovieCatalog movieCatalog;

    private CustomerPreferenceDao customerPreferenceDao;

    @Autowired

    public MovieRecommender(CustomerPreferenceDao customerPreferenceDao) {

        this.customerPreferenceDao = customerPreferenceDao;

    }

    // ...

}

It is also possible to provide all beans of a particular type from the ApplicationContext by adding the annotation to a field or method that expects an array of that type:

public class MovieRecommender {

    @Autowired

    private MovieCatalog[] movieCatalogs;

    // ...

}

The same applies for typed collections:

public class MovieRecommender {

    private Set<MovieCatalog> movieCatalogs;

    @Autowired

    public void setMovieCatalogs(Set<MovieCatalog> movieCatalogs) {

        this.movieCatalogs = movieCatalogs;

    }

    // ...

}