6、Spring之基于xml的自动装配
6.1、场景模拟
6.1.1、创建UserDao接口及实现类
package org.rain.spring.dao;
/**
* @author liaojy
* @date 2023/8/5 - 11:05
*/
public interface UserDao {
void saveUser();
}
package org.rain.spring.dao.impl;
import org.rain.spring.dao.UserDao;
/**
* @author liaojy
* @date 2023/8/5 - 11:08
*/
public class UserDaoImpl implements UserDao {
public void saveUser() {
System.out.println("保存成功");
}
}
6.1.2、创建UserService接口及实现类
package org.rain.spring.service;
/**
* @author liaojy
* @date 2023/8/5 - 11:10
*/
public interface UserService {
void saveUser();
}
package org.rain.spring.service.impl;
import org.rain.spring.dao.UserDao;
import org.rain.spring.service.UserService;
/**
* @author liaojy
* @date 2023/8/5 - 11:23
*/
public class UserServiceImpl implements UserService {
private UserDao userDao;
public UserDao getUserDao() {
return userDao;
}
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
public void saveUser() {
userDao.saveUser();
}
}
6.1.3、创建UserController
package org.rain.spring.controller;
import org.rain.spring.service.UserService;
/**
* @author liaojy
* @date 2023/8/5 - 11:32
*/
public class UserController {
private UserService userService;
public UserService getUserService() {
return userService;
}
public void setUserService(UserService userService) {
this.userService = userService;
}
public void saveUser(){
userService.saveUser();
}
}
6.1.4、配置bean
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="userDao" class="org.rain.spring.dao.impl.UserDaoImpl"></bean>
<bean id="userService" class="org.rain.spring.service.impl.UserServiceImpl">
<property name="userDao" ref="userDao"></property>
</bean>
<bean id="userController" class="org.rain.spring.controller.UserController">
<property name="userService" ref="userService"></property>
</bean>
</beans>
6.1.5、测试
@Test
public void testAutoWireByXML(){
ApplicationContext ioc = new ClassPathXmlApplicationContext("spring-autowire.xml");
UserController userController = ioc.getBean(UserController.class);
userController.saveUser();
}
6.2、两种自动装配方式
6.2.1、方式一：byType(常用)
6.2.1.1、配置bean
注意：
若在IOC中，没有任何一个兼容类型的bean能够为属性赋值，则该属性不装配，即值为默认值null
若在IOC中，有多个兼容类型的bean能够为属性赋值，则抛出异常NoUniqueBeanDefinitionException
<bean id="userDao" class="org.rain.spring.dao.impl.UserDaoImpl"></bean>
<!--
autowire属性：指定自动装配的策略，为bean的类类型（或接口类型）的属性自动赋值
byType：根据要赋值的属性的类型，匹配ioc容器中的兼容类型的bean，为属性赋值
-->
<bean id="userService" class="org.rain.spring.service.impl.UserServiceImpl" autowire="byType"></bean>
<bean id="userController" class="org.rain.spring.controller.UserController" autowire="byType"></bean>
6.2.1.2、测试
6.2.2、方式二：byName(后备)
6.2.2.1、配置bean
当在IOC中，有多个兼容类型的bean能够为属性赋值时；可以使用byName的方式，匹配id和属性名相同的bean为属性赋值
<bean id="userDao" class="org.rain.spring.dao.impl.UserDaoImpl"></bean>
<bean id="userDaotwo" class="org.rain.spring.dao.impl.UserDaoImpl"></bean>
<!--
autowire属性：指定自动装配的策略，为bean的类类型（或接口类型）的属性自动赋值
byName：根据要赋值的属性的名称，匹配ioc容器中的对应id的bean，为属性赋值
-->
<bean id="userService" class="org.rain.spring.service.impl.UserServiceImpl" autowire="byName"></bean>