<?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.

@Autowired

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;
} // ...
}

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