Spring:构造函数属性注入

作者: LiHui 分类: Spring 发布时间: 2018-07-28 23:44

通过构造函数注入属性基本和set方法注入类似,唯一不同的就是容器里面的标签不同

比如Demo类

package com.lihuia.ioc;

/**
* Copyright (C), lihuia.com
* FileName: Demo
* Author: lihui
* Date: 2018/7/28
*/

public class Demo {

private Girl girl;

public Demo() {}
public Demo(Girl girl) {
this.girl = girl;
}

public void sayHello() {
System.out.println("Hello, " + girl.myGirl());
}
}

这里通过构造函数传入girl,同时Girl类不变

package com.lihuia.ioc;

/**
* Copyright (C), lihuia.com
* FileName: Girl
* Author: lihui
* Date: 2018/7/28
*/

public class Girl {

public String myGirl() {
return "Lucy";
}
}

此时XML换了一个标签

<?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="demo" class="com.lihuia.ioc.Demo">
<constructor-arg name="girl" ref="girl"></constructor-arg>
</bean>
<bean id="girl" class="com.lihuia.ioc.Girl"></bean>

</beans>

通过constructor-arg,从字面意思也可以看出来是构造函数的参数,单要注意的是:

(1)name表示的是构造函数里传入的参数,如果构造函数里传入girl1,name这里constructor-arg的name也必须是girl1,保持一致

(2)ref引用的是本XML里已经存在的Girl类型的bean

测试类没什么变化

package com.lihuia.ioc;

import javax.annotation.Resource;

import org.testng.annotations.Test;

import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.testng.AbstractTestNGSpringContextTests;

/**
* Copyright (C), lihuia.com
* FileName: DemoTest
* Author: lihui
* Date: 2018/7/28
*/

@ContextConfiguration(locations = {"classpath:ioc.xml"})
public class DemoTest extends AbstractTestNGSpringContextTests {

@Resource(name = "demo")
private Demo demo;

@Test
public void testSayHello() {
demo.sayHello();
}
}

如果构造函数要传入多个参数,比如新增一个message,来传达要对girl说的话

package com.lihuia.ioc;

/**
* Copyright (C), lihuia.com
* FileName: Demo
* Author: lihui
* Date: 2018/7/28
*/

public class Demo {

private Girl girl;
private String message;

public Demo() {}
public Demo(Girl girl, String message) {
this.girl = girl;
this.message = message;
}

public void sayHello() {
System.out.println("Hello, " + girl.myGirl() + message);
}
}

此时girl的传入方式不变,只需要在XML里新增一个message的参数声明

<?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="demo" class="com.lihuia.ioc.Demo">
<constructor-arg name="girl" ref="girl"></constructor-arg>
<constructor-arg name="message" value=", Congratulations"></constructor-arg>
</bean>
<bean id="girl" class="com.lihuia.ioc.Girl"></bean>

</beans>

任意新增的参数都可以在demo bean里进行添加

纯属恶搞

浙ICP备16024533号

浙公网安备 33010802007459号