4、IOC创建对象

1. 通过无参构造方法来创建

1）User

pojo包

public class User{
    private String name;
    public User(){
        System.out.println("User的无参构造");
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void show(){
        System.out.println("name = " + name);
    }
}

2）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">
    <bean id="user" class="cn.edu.jxust.pojo.User">
        <property name="name" value="隔竹" />
    </bean>
</beans>

3）MyTest

import cn.edu.jxust.pojo.User;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        User user = (User) context.getBean("user");
        user.show();
    }
}

2. 通过有参构造方法来创建

1）UserT

pojo包

package cn.edu.jxust.pojo;
public class UserT {
    private String name;
    public UserT(String name){
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void show(){
        System.out.println("name = " + name);
    }
}

2）beans.xml

第一种：根据index参数下标设置

<?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">
<!--    第一种方式根据index参数下标设置-->
    <!--
    <bean id="userT" class="cn.edu.jxust.pojo.UserT" >
        <constructor-arg index="0" value="隔竹" />
    </bean>
    -->
</beans>

第二种：根据参数名字设置

<?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">
<!-- 第二种根据参数名字设置 -->
    <!--<bean id="userT" class="cn.edu.jxust.pojo.UserT" >
        <constructor-arg name="name" value="隔竹隔竹" />
    </bean>-->
</beans>

第三种：根据参数类型设置

<?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">
    <!-- 第三种根据参数类型设置 -->
    <bean id="userT" class="cn.edu.jxust.pojo.UserT">
        <constructor-arg type="java.lang.String" value="隔竹隔竹隔竹" />
    </bean>
</beans>

3）输出结果

import cn.edu.jxust.pojo.User;
import cn.edu.jxust.pojo.UserT;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        UserT user = (UserT) context.getBean("userT");
        user.show();
    }
}