Spring自动装配

 根据名称自动装配：autowire="byName"

         -自动去IOC容器中找与属性名同名的引用的对象，并自动注入

---

package loaderman.d_auto;


import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App {

    // 创建容器对象
    private ApplicationContext ac =
            new ClassPathXmlApplicationContext("loaderman/d_auto/bean.xml");

    @Test
    public void testExecuteAction() {
        // 从容器中获取Action
        UserAction userAction = (UserAction) ac.getBean("userAction");
        userAction.execute();
    }
}

package loaderman.d_auto;

public class UserAction {

    // Service: springIOC容器注入
    private UserService userService;
    public void setUserService(UserService userService) {
        this.userService = userService;
    }


    public String execute() {
        userService.save();
        return null;
    }
}

package loaderman.d_auto;

public class UserDao {

    public void save() {
        System.out.println("DB:保存用户");
    }
}

package loaderman.d_auto;

public class UserService {

    private UserDao userDao; // = new UserDao();
    // IOC：对象的创建交给spring的外部容器完成
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    public void save() {
        userDao.save();
    }
}

<?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:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd" default-autowire="byType">
    <!-- ###############自动装配############### -->  
    <bean id="userDao" class="loaderman.d_auto.UserDao"></bean>
    <bean id="userService" class="loaderman.d_auto.UserService"></bean>
    <!-- 如果根据类型自动装配： 必须确保IOC容器中只有一个该类型的对象 -->
    <bean id="userAction" class="loaderman.d_auto.UserAction"></bean>
    <!--   报错： 因为上面已经有一个该类型的对象，且使用了根据类型自动装配
    <bean id="userService_test" class="loaderman.d_auto.UserService" autowire="byType"></bean>
     -->
</beans>      

总结：

         Spring提供的自动装配主要是为了简化配置； 但是不利于后期的维护。

         (一般不推荐使用)