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