Spring学习随记1

spring-IOC之依赖注入

官网地址：

https://docs.spring.io/spring/docs/5.2.2.RELEASE/spring-framework-reference/core.html#beans-factory-collaborators

涉及名词：

IOC：Inversion of Control控制反转
DI：dependency injection  依赖注入
IOC和DI之间的关系：IOC是一种解耦思想，DI是IOC的一种实现方式

依赖注入的实现

		1.构造器注入2.setter方法注入3.接口注入（传闻早期有，但不人性故被移除，自由鸡没找相关文档，!·_·!）

代码结构

构造器注入

代码实现

package com.csh.test.project;import com.csh.test.project.service.ManagementService;
import org.springframework.context.support.ClassPathXmlApplicationContext;/*** Hello world!*/
public class App {public static void main(String[] args) {//加载xml元数据ClassPathXmlApplicationContext cxt = new ClassPathXmlApplicationContext("beanXml.xml");// 从容器中获取ManagementService beanManagementService managementService = (ManagementService) cxt.getBean("managementService");}
}

EmployeeService.java

package com.csh.test.project.service.impl;import com.csh.test.project.service.EmployeeService;/*** Created on 2020-01-17.** @author chensihong*/
public class EmployeeServiceImpl implements EmployeeService {public EmployeeServiceImpl() {//initSystem.err.println("EmployeeServiceImpl constructor");}@Overridepublic void print() {System.err.println("EmployeeServiceImpl print!!!");}
}

ManagementService.java

package com.csh.test.project.service.impl;import com.csh.test.project.service.EmployeeService;
import com.csh.test.project.service.ManagementService;/*** Created on 2020-01-17.** @author chensihong*/
public class ManagementServiceImpl implements ManagementService {public ManagementServiceImpl(EmployeeService employeeService) {//initSystem.err.println("ManagementServiceImpl");employeeService.print();}
}

增加Schema

红圈部分为引入模块的名字

beanXml.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"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><!--    <context:component-scan base-package="com.csh.test.project.service"/>--><bean id="employeeService" class="com.csh.test.project.service.impl.EmployeeServiceImpl"></bean><bean id="managementService" class="com.csh.test.project.service.impl.ManagementServiceImpl"><constructor-arg ref="employeeService"/></bean>
</beans>

结果

setter方法注入

beanXml.xml

package com.csh.test.project.service.impl;import com.csh.test.project.service.EmployeeService;
import com.csh.test.project.service.ManagementService;/*** Created on 2020-01-17.** @author chensihong*/
public void setEmployeeService(EmployeeService employeeService) {System.out.println("setter mother");employeeService.print();}public ManagementServiceImpl() {//initSystem.err.println("ManagementServiceImpl");}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><bean id="employeeService" class="com.csh.test.project.service.impl.EmployeeServiceImpl"></bean><bean id="managementService" class="com.csh.test.project.service.impl.ManagementServiceImpl"><property name="employeeService" ref="employeeService"/></bean>
</beans>

结果

拓展

循环依赖

使用构造函数注入，Class A 引Class B，Class B引Class A，导致死循环，			           bean无法创建成功，官方建议修改源代码，不要使用构造函数注入，但可以使用setter方法解决
更多相关xml配置查看[官方文档](https://docs.spring.io/spring/docs/5.2.2.RELEASE/spring-framework-reference/core.html#beans-value-element)