Java框架spring Boot学习笔记：注入对象类型属性

Posted 2020-10-13 pyqb

使用set方法注入对象属性

编写UserDao.java文件

1 package com.example.spring;
2 
3 public class UserDao {
4     public void print(){
5         System.out.println("Dao print.");
6     }
7 }

 

编写UserService.java文件

 1 package com.example.spring;
 2 
 3 public class UserService {
 4     //1、定义dao类型属性
 5     private UserDao userDao;
 6     //2、生成set方法
 7     public void setUserDao(UserDao userDao){
 8         this.userDao = userDao;
 9     }
10 
11     public void print(){
12         System.out.println("Service print.");
13         //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
14         //UserDao dao = new UserDao();
15         //dao.print();
16         userDao.print();
17     }
18 }

 

编写Beans.xml文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
 5 
 6     <bean id="userDao" class="com.example.spring.UserDao"></bean>
 7 
 8     <bean id="userService" class="com.example.spring.UserService" >
 9         <property name="userDao" ref="userDao"></property>
10     </bean>
11 </beans>

注意注入的属性是UserDao类的id。

 

编写Application.java

 1 package com.example.spring;
 2 
 3 import org.springframework.context.support.AbstractApplicationContext;
 4 import org.springframework.context.support.ClassPathXmlApplicationContext;
 5 
 6 public class Application {
 7     public static void main(String[] args) {
 8         //bean配置文件所在位置 D:\\\\IdeaProjects\\\\spring\\\\src\\\\Beans.xml
 9         //使用AbstractApplicationContext容器
10         AbstractApplicationContext context = new ClassPathXmlApplicationContext("file:D:\\\\IdeaProjects\\\\spring\\\\src\\\\Beans.xml");
11         //得到配置创建的对象
12         UserService userService = (UserService) context.getBean("userService");
13         userService.print();
14     }
15 }

 

运行输出

Service print.
Dao print.