[Java知识库]Spring5学习笔记3

此处重点有三：

1. 用构造函数赋值的bean
2. 起别名
3. 将所有的bean导入一个总表中.

1. 创建实体类

User.class

package com.chen.pojo;

public class User {
    private String name;
    
    public User(String name) {
        this.name = name;
    }
    
    public void show() {
        System.out.println("name=" + name);
    }
}

UserT.class

package com.chen.pojo;

public class UserT {
    private String name;

    public UserT(){
        System.out.println("UserT被創建了");
    }

    public String getName() {
        return name;
    }

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

    public void show() {
        System.out.println("name=" + name);
    }
}

2.创建Spring容器xml文件.

每个xml可以对应一个实体类,然后汇总到一个总的xml中使用.

applicationContext.xml

<?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">
    <!--  将其他单个的xml导入到这个xml中   -->
    <import resource="beans.xml"/>
    <import resource="beans1.xml"/>
    <import resource="beans2.xml"/>
</beans>

beans.xml

<?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">
    <!--使用Spring创建对象，在spring中这些都称为bean-->
    <!--
        id = 对象名
        class = new 的对象
        property 相对于给对象中的属性赋值
            name = 属性名
            value = 属性值
            ref = 引用类型的值
    -->

    <!--    2.1下标    -->
    <!--    <bean id="user" class="com.chen.pojo.User">-->
    <!--        <constructor-arg name="name" index="0" value="秦寿"/>-->
    <!--    </bean>-->

    <!--    2.2类型(不建议使用)    -->
    <!--    <bean id="user" class="com.chen.pojo.User">-->
    <!--        <constructor-arg name="name" type="java.lang.String" value="秦寿2"/>-->
    <!--    </bean>-->

    <!--3.直接通过参数名(常用) -->
    <bean id="user" class="com.chen.pojo.User">
        <!--    通过有参构造函数赋值      -->
        <constructor-arg name="name" value="秦寿"/>
    </bean>

    <!--    此处的name是起别名   -->
    <bean id="userT" class="com.chen.pojo.UserT" name="userT2 userT3">
        <!--  配置的时候就会创建好对象,实际上是用set方法赋值的,此处用的是UserT的setName方法-->
        <property name="name" value="kuangstudy.com"/>
    </bean>
</beans>

beans1.xml

<?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">

</beans>

beans2.xml

<?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">

</beans>

3.在test/java文件夹内创建MyTest.class进行测试

import com.chen.pojo.User;
import com.chen.pojo.UserT;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        //1.拿到容器
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        //2.用哪个对象get哪个对象
        User user =(User) context.getBean("user");
        user.show();
        System.out.println();

        UserT userT =(UserT) context.getBean("userT");
        userT.show();
        UserT userT2 =(UserT) context.getBean("userT2");
        userT2.show();
        UserT userT3 =(UserT) context.getBean("userT3");
        userT3.show();
    }
}