spring person

IOC： 由spring 进行创建、管理、配置

官网：https://docs.spring.io/spring/docs/5.2.7.RELEASE/spring-framework-reference/core.html#beans-child-bean-definitions

一个简单的例子

准配工作：导包

1、pojo实体类

package com.wt.pojo;

public class Person {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                '}';
    }
}

2、配置元数据

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">
<!--
id 唯一变量名与实例化容器相呼应
class 为 实体类
property 为实体类的具体属性 value 为值
spring实现类的实例化和赋值 而不是通过传统的 new
-->
    <bean id="person" class="com.wt.pojo.Person">
        <property name="name" value="tom"/>
     </bean>

</beans>

3、实例化容器

import com.wt.pojo.Person;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    @Test
    public void showResult(){
        ApplicationContext context = new ClassPathXmlApplicationContext( "beans.xml");
        // person 对应配置文件的 id
        Person person = (Person) context.getBean("person");
        String personString = person.toString();
        System.out.println(personString);
    }
}

new ClassPathXmlApplicationContext

idea快捷键 new CPX

注意：<property name="name" value="tom"/>

value 是普通变量

ref 指向自定义的类别名

例子

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

        <bean id="daoHello" class="com.wt.dao.UserDaoHello" />
        <bean id="daoImp" class="com.wt.dao.UserDaoImp" />
        <bean id="serviceImp" class="com.wt.service.UserServiceImp">
            <property name="userDao" ref="daoHello" />
        </bean>

</beans>