Java框架spring 学习笔记（八）：注入对象类型属性

使用set方法注入对象属性

编写UserDao.java文件

 package com.example.spring;

 public class UserDao {
     public void print(){
         System.out.println("Dao print.");
     }
 }

编写UserService.java文件

 package com.example.spring;

 public class UserService {
     //1、定义dao类型属性
     private UserDao userDao;
     //2、生成set方法
     public void setUserDao(UserDao userDao){
         this.userDao = userDao;
     }

     public void print(){
         System.out.println("Service print.");
         //如果不使用Spring对象属性注入的方式，想在service中调用dao里面的方法，必须先new一个dao的对象
         //UserDao dao = new UserDao();
         //dao.print();
         userDao.print();
     }
 }

编写Beans.xml文件

 <?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="com.example.spring.UserDao"></bean>

     <bean id="userService" class="com.example.spring.UserService" >
         <property name="userDao" ref="userDao"></property>
     </bean>
 </beans>

注意注入的属性是UserDao类的id。

编写Application.java

 package com.example.spring;

 import org.springframework.context.support.AbstractApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;

 public class Application {
     public static void main(String[] args) {
         //bean配置文件所在位置 D:\\IdeaProjects\\spring\\src\\Beans.xml
         //使用AbstractApplicationContext容器
         AbstractApplicationContext context = new ClassPathXmlApplicationContext("file:D:\\IdeaProjects\\spring\\src\\Beans.xml");
         //得到配置创建的对象
         UserService userService = (UserService) context.getBean("userService");
         userService.print();
     }
 }

运行输出

Service print.
Dao print.