Java框架spring 学习笔记（六）：属性注入

属性注入：创建对象的时候，向类里面的属性设置值。

Java属性注入有三种方法：

1. 使用set方法注入
2. 有参数构造注入
3. 使用接口注入

Spring框架里面的属性注入方式

1. 有参数构造属性注入
2. set方法属性注入

有参数构造属性注入

编写User.java

package com.example.spring;

public class User {
    private String name;
    private Integer age;
    private String country;

    //基于构造函数的属性注入
    public User(String name, Integer age, String country) {
        this.name = name;
        this.age = age;
        this.country = country;
    }

    public String toString() {
        return name + " is " + age + " years old, living in " + country;
    }
}

编写Beans.xml，使用constructor-arg为属性赋值

<?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="user" class="com.example.spring.User" >
        <constructor-arg name="name" type="java.lang.String" value="Jacky" />
        <constructor-arg name="age" type="java.lang.Integer" value="22"/>
        <constructor-arg name="country" type="java.lang.String" value="China"/>
    </bean>

</beans>

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");
        User user = (User)context.getBean("user");
        System.out.println(user);
    }
}

运行输出

Jacky is 22 years old, living in China

set方法属性注入

编写User.java

package com.example.spring;

public class User {
    private String name;
    private Integer age;
    private String country;

    //基于set方法的属性注入
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public void setCountry(String country) {
        this.country = country;
    }
    
    public String toString() {
        return name + " is " + age + " years old, living in " + country;
    }
}

编写Beans.xml，使用property关键字为属性赋值

<?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="user" class="com.example.spring.User" >
        <property name="name" value="Jacky"></property>
        <property name="age" value="22"></property>
        <property name="country" value="China"></property>
    </bean>

</beans>

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");
        User user = (User)context.getBean("user");
        System.out.println(user);
    }
}

运行输出

Jacky is 22 years old, living in China