Spring（学习笔记）IOC

概念

IOC 控制反转，是Spring的核心，贯穿始终。对于Spring框架来说，就是通过Spring来负责控制对象的生命周期和对象间的关系。
IOC另外的名字叫依赖注入，就是由IOC容器在运行期间，动态的将某种依赖关系注入到对象之中。所以依赖注入（DI）与控制反转（IOC）是从不同角度的描述的同一件事，就是指通过引入IOC容器，利用依赖注入的方式，实现对象之间的解耦。
IOC 控制反转：创建对象实例的控制权从代码控制剥离到IOC容器控制，实际就是XML文件控制，侧重于原理。
DI 依赖注入：在创建对象实例时，为这个对象注入属性值或者其他对象实例，侧重于实现。

优点

• 降低组件之间的耦合
• 提高开发效率和产品质量
• 统一标准，提高模块的复用性
• 模块具有热插拔特性

代码示例

github：https://github.com/ChaoHappy/SpringIoc/tree/master/ioc
pom.xml 引入依赖

<properties>
			<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
			<spring.version>4.1.7.RELEASE</spring.version>
  </properties>
  <dependencies>
	    <dependency>
	      <groupId>junit</groupId>
	      <artifactId>junit</artifactId>
	      <version>4.10</version>
	      <scope>test</scope>
	    </dependency>
	    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
		 <dependency>
		    <groupId>javax.servlet</groupId>
		    <artifactId>javax.servlet-api</artifactId>
		    <version>4.0.1</version>
		    <scope>provided</scope>
		 </dependency>
	 	<!-- 添加Spring支持 -->
		<!-- 核心包 -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>${spring.version}</version>
		</dependency>
		
		<!-- Spring IOC的基础实现，包含访问配置文件、创建和管理bean等 -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-beans</artifactId>
			<version>${spring.version}</version>
		</dependency>
		
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${spring.version}</version>
		</dependency>
		
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context-support</artifactId>
			<version>${spring.version}</version>
		</dependency>
	
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-web</artifactId>
			<version>${spring.version}</version>
		</dependency>
	
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>${spring.version}</version>
		</dependency>
	
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-tx</artifactId>
			<version>${spring.version}</version>
		</dependency>
		
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-aop</artifactId>
			<version>${spring.version}</version>
		</dependency>
	
	
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-aspects</artifactId>
			<version>${spring.version}</version>
		</dependency>
	
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-jdbc</artifactId>
			<version>${spring.version}</version>
		</dependency>
		
		<dependency>
		    <groupId>org.springframework</groupId>
		    <artifactId>spring-test</artifactId>
		    <version>${spring.version}</version>
		</dependency>
  </dependencies>

application-context.xml 声明示例Bean

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.1.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">

	<bean id="helloWorldServoce" class="com.spring.service.impl.HelloWorldServiceImpl">
		<property name="content" value="你好"></property>
	</bean>
</beans>

HelloWorldService

package com.spring.service;

public interface HelloWorldService {

	String say();
}

HelloWorldServiceImpl

package com.spring.service.impl;

import com.spring.service.HelloWorldService;

public class HelloWorldServiceImpl implements HelloWorldService {

	private String content;

	public String getContent() {
		return content;
	}

	public void setContent(String content) {
		this.content = content;
	}

	public String say() {
		return content;
	}
}

测试用例

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"/application-context.xml"})
public class IocTest1 {

	@Autowired
	private HelloWorldService	helloService;

   //Spring容器加载获取示例对象
	@Test
	public void say() {
		ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("application-context.xml");
		HelloWorldService helloWorldService = (HelloWorldService) applicationContext.getBean("helloWorldServoce");
		System.out.println(helloWorldService.say());
	}

	//注解自动注入的方式
	@Test
	public void sayAutowired() {
		System.out.println(helloService.say());
	}
}