Spring中装配bean的三种主要方式

1.自动化配置

package com.springinaction.test;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration//告诉spring这是一个配置类
@ComponentScan//扫描组件
public class CDPlayerConfig {

}

package com.springinaction.test;

import org.springframework.stereotype.Component;

@Component
public class SgtPeppers implements CompactDisc{//CompactDisc是一个接口

	private String title = "Sgt. Pepper's Linel Hearts Cloub Band";
	private String artist = "The Beatles";
	
	@Override
	public void play() {
		System.out.println("Playing " + title + " by " + artist);
	}

}

2.基于java的显示配置：要在java中声明bean，我们需要一个方法

package com.springinaction.test;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class CDPlayerConfig {

	@Bean//@Bean会告诉Spring这个方法将返回一个对象，该对象要注册为Spring应用上下文中的bean
	public CompactDisc sgtPeppers(){
		return new SgtPeppers();
	}
}

package com.springinaction.test;

import org.springframework.stereotype.Component;

//这里没有哦
public class SgtPeppers implements CompactDisc{

	private String title = "Sgt. Pepper's Linel Hearts Cloub Band";
	private String artist = "The Beatles";
	
	@Override
	public void play() {
		System.out.println("Playing " + title + " by " + artist);
	}

}

3.基于XML的显示配置

<?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.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"
    >
	<!-- 简单bean引用-->
	<bean id="compactDisc" class="com.springinaction.test.CompactDisc"/>
	<bean id="cdPlayer" class="com.springinaction.test.CdPlayer">
        <!-- 构造器中参数为CompactDisc对象 -->
        <constructor-arg ref="compactDisc"/>
    </bean>
	</beans>

不管采用扫描方式，这些技术都描述了Spring应用中的组件以及这些组件之间的关系；

建议尽可能的使用自动化配置，以避免显示配置带来的维护成本；

如果你确实需要显示配置Spring的话，应该优先选择基于Java的配置，它比基于XML的配置更强大、类型安全并且易于重构！