Spring Bean 的两种注入方式

1.set方法注入：
.xml配置文件：

 <bean id="userDao" class="com.itlaobin.dao.impl.UserDaoImpl"></bean>
 <bean id="userService" class="com.itlaobin.service.impl.UserserviceImpl">
        <property name="userDao" ref="userDao"></property>
 </bean>

set方法：

   private  UserDao userDao;
    public void setUserDao(UserDao userDao) {
    
    
        this.userDao = userDao;
    }

表现层UserController

 ApplicationContext app=new ClassPathXmlApplicationContext("applicationContext.xml");
        Userservice userService = (Userservice) app.getBean("userService");
        userService.save();

set中p命名空间的注入：
（1）在命名空间中加入

xmlns:p="http://www.springframework.org/schema/p"

（2）配置文件：

<bean id="userService" class="com.itlaobin.service.impl.UserserviceImpl" p:userDao-ref="userDao"  />

2.（带参）构造方法注入：
service的实现带参构造方法

 private  UserDao userDao;
    public UserserviceImpl(UserDao userDao) {
    
    
        this.userDao = userDao;
    }
    public UserserviceImpl() {
    
    
    }

配置文件

 <bean id="userDao" class="com.itheima.dao.impl.UserDaoImpl"></bean>
<bean id="userService" class="com.itheima.service.impl.UserserviceImpl">
        <constructor-arg name="userDao" ref="userDao"></constructor-arg>
</bean>