Spring5入门

使用Spring DI实现的入门案例：松耦合、可扩展的消息渲染程序

项目目录结构

代码（基于XML配置的实现）

0、pom引入

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.jay</groupId>
  <artifactId>chap02</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  <dependencies>
  	<!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-context</artifactId>
	    <version>5.1.6.RELEASE</version>
	</dependency>
  </dependencies>
</project>

1、接口

package com.jay.decoupled;

public interface MessageProvider {
	String getMessage();
}


public interface MessageRender {
	void render();

	/* MessageProvider是MessageRender的依赖项 */
	void setMessageProvider(MessageProvider provider);
	MessageProvider getMessageProvider();
}

2、实现类

public class HelloWorldMessageProvider implements MessageProvider{
	@Override
	public String getMessage() {
		return "Hello World!!!";
	}
}

public class HelloWorldMessageRender implements MessageRender{
	
	public MessageProvider messageProvider;
	@Override
	public void render() {
		if (messageProvider==null) {
			throw new RuntimeException("you must set the property of messageProvider of class"+HelloWorldMessageRender.class.getName());
		}
		System.out.println(messageProvider.getMessage());
	}
	@Override
	public void setMessageProvider(MessageProvider provider) {
		messageProvider = provider ;
	}
	@Override
	public MessageProvider getMessageProvider() {
		return this.messageProvider;
	}
}

3、入口

public class HelloWorldSpringDI {
	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext("spring/app-context.xml");
		MessageRender render = ctx.getBean("render",MessageRender.class);
		render.render();
	}
}

4、配置文件

<?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:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<!-- 定义Bean -->
	<bean id="provider" class="com.jay.decoupled.HelloWorldMessageProvider"></bean>
	<!-- p:messageProvider-ref="provider" 告诉spring，bean的属性messageProvider应该与另一个bean一起注入 -->
	<bean id="render" class="com.jay.decoupled.HelloWorldMessageRender" p:messageProvider-ref="provider"></bean>
</beans>

代码（基于注解的实现）

1、配置类

/*表明这是一个配置类*/
@Configuration
public class HelloWorldConfiguration {
	@Bean(name="provider")
	public MessageProvider	provider() {
		return new HelloWorldMessageProvider();
	}
	@Bean(name="render")
	public MessageRender render() {
		HelloWorldMessageRender messageRender = new HelloWorldMessageRender();
		messageRender.setMessageProvider(provider());
		return messageRender;
	}
}

2、入口

public class HelloWorldSpringDIAnnotation {
	public static void main(String[] args) {
		ApplicationContext ctx = new AnnotationConfigApplicationContext(HelloWorldConfiguration.class);
		MessageRender render = ctx.getBean("render",MessageRender.class);
		render.render();
	}
}

结果输出：