Spring中基于Java的配置@Configuration和@Bean用法

spring中为了减少xml中配置，可以声明一个配置类（例如SpringConfig）来对bean进行配置。

一、首先，需要xml中进行少量的配置来启动Java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:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
            http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
            http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">
   <context:component-scan base-package="SpringStudy.Model">
    </context:component-scan>
</beans>  

二、定义一个配置类

用@Configuration注解该类，等价 与XML中配置beans；用@Bean标注方法等价于XML中配置bean。

代码如下：

package SpringStudy;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import SpringStudy.Model.Counter;
import SpringStudy.Model.Piano;  

@Configuration
public class SpringConfig {  

    @Bean
    public Piano piano(){
        return new Piano();
    }
    @Bean(name = "counter")
    public Counter counter(){
        return  new Counter(12,"Shake it Off",piano());
    }
}  

三、基础类代码

package SpringStudy.Model;  

public class Counter {
    public  Counter() {
    }  

    public  Counter(double multiplier, String song,Instrument instrument) {
        this.multiplier = multiplier;
        this.song = song;
        this.instrument=instrument;
    }  

    private double multiplier;  

    private String song;  

    @Resource
    private Instrument instrument;  

    public double getMultiplier() {
        return multiplier;
    }  

    public void setMultiplier(double multiplier) {
        this.multiplier = multiplier;
    }  

    public String getSong() {
        return song;
    }  

    public void setSong(String song) {
        this.song = song;
    }  

    public Instrument getInstrument() {
        return instrument;
    }  

    public void setInstrument(Instrument instrument) {
        this.instrument = instrument;
    }  

}  

Piano类

package SpringStudy.Model;  

public class Piano {
    private String name="Piano";
    private String sound;  

    public String getName() {
        return name;
    }  

    public void setName(String name) {
        this.name = name;
    }  

    public String getSound() {
        return sound;
    }  

    public void setSound(String sound) {
        this.sound = sound;
    }  

}  

四、调用测试类

package webMyBatis;  

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import SpringStudy.Model.Counter;  

public class SpringTest {
    public static void main(String[] args) {
        //ApplicationContext ctx = new ClassPathXmlApplicationContext("spring/bean.xml");// 读取bean.xml中的内容
        ApplicationContext annotationContext = new AnnotationConfigApplicationContext("SpringStudy");
        Counter c = annotationContext.getBean("counter", Counter.class);// 创建bean的引用对象
        System.out.println(c.getMultiplier());
        System.out.println(c.isEquals());
        System.out.println(c.getSong());
            System.out.println(c.getInstrument().getName());
    }
}  

注意：如果是在xml中配置beans和bean的话，或者使用自动扫描调用的话，代码为

ApplicationContext ctx = new ClassPathXmlApplicationContext("spring/bean.xml");// 读取bean.xml中的内容
Counter c = ctx.getBean("counter", Counter.class);// 创建bean的引用对象

五、运行结果

12.0
false
Shake it Off
Piano