基于Java的容器注解@Bean

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本文详细介绍了Spring框架中@Bean注解的使用方法，包括如何使用@Bean定义Bean、自定义Bean名称、定义初始化和销毁方法等。并通过示例代码展示了@Bean在实际应用中的配置方式。

日期： 2016-7-19

内容： Spring的@Bean注解

1、 @Beab标识一个用于配置和初始化一个由SpringIoC日那个气的新对象方法，类似于xml文件的<bean/>:

2、可以在Spring的@Component注解的类中使用@Bean注解任何方法(仅仅是可以)，但是一般不用@Component，更常用的是@Configuration(一个配置类)。

@Configuration
public class AppConfig()
{
    @Bean
    public MyService myService()
    {
         return new MyServiceImpl();
    }
}

使用如上的注解相当于在配置文件中使用如下的配置：

<beans>
	<bean id="myService" class="com.hello.MyServiceImpl"></bean/>
</beans>

自定义Bean的name：

public class Foo
{
<span style="white-space:pre">	</span>//do somethings
}


@Configuration
public class AppConfig
{
<span style="white-space:pre">	</span>@Bean(name="myFoo")
<span style="white-space:pre">	</span>public Foo foo()
<span style="white-space:pre">	</span>{
<span style="white-space:pre">		</span>return new Foo();
<span style="white-space:pre">	</span>}
}

@Bean可以定义初始化方法和销毁方法： initMethod,destoryMethod;

public class Foo
{
	public void init()
	{
		System.out.println("我是初始化方法！");
	}
}

public class Bar()
{
	public void destory()
	{
		System.out.println("我执行了销毁方法！");
	}
}

//调用初始化和销毁方法配置
@Configuration
public class TestBean
{
	@Bean(initMethod="init")
	public Foo getFoo()
	{
		return new Foo();
	}

	@Bean(destoryMethod="destory")
	public void getBar()
	{
		return new Bar();
	}
}

实例演示：

package com.spring_bean.inter;

public interface Store {

}

package com.spring_bean.impl;

import com.spring_bean.inter.Store;

public class StringStore implements Store {

}

package com.spring_bean.service;

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

import com.spring_bean.impl.StringStore;
import com.spring_bean.inter.Store;

@Configuration
public class StoreConfig {

	@Bean(name="store")
	public Store getStringStore()
	{
		return new StringStore();
	}
}

package com.spring_bean.test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.spring_bean.inter.Store;
import com.spring_bean.service.StoreConfig;

public class TestSpringBean {

	@Test
	public void testBean()
	{
		//加载配置文件
		//@SuppressWarnings("resource")
		ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext_Bean.xml");
		
		//初始化加载的Bean
		StoreConfig sc = (StoreConfig)context.getBean("store");
		//Store sc = (Store)context.getBean("stringStore");
		//输出bean的名字
		System.out.println(sc.getClass().getName());
	}
}

配置文件：

<?xml version="1.0" encoding="UTF-8"?>  
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" 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:util="http://www.springframework.org/schema/util" xmlns:jdbc="http://www.springframework.org/schema/jdbc"  
    xmlns:cache="http://www.springframework.org/schema/cache"  
    xsi:schemaLocation="  
    http://www.springframework.org/schema/context  
    http://www.springframework.org/schema/context/spring-context.xsd  
    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/jdbc  
    http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd  
    http://www.springframework.org/schema/cache  
    http://www.springframework.org/schema/cache/spring-cache-3.1.xsd  
    http://www.springframework.org/schema/aop  
    http://www.springframework.org/schema/aop/spring-aop.xsd  
    http://www.springframework.org/schema/util  
    http://www.springframework.org/schema/util/spring-util.xsd">  
	
	 <!-- 开启Spring注解 -->
	<context:annotation-config></context:annotation-config>
	
</beans>

执行结果：

异常描述：

org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStringStore' is defined
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:687)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1168)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:281)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
	at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:956)
	at com.spring_bean.test.TestSpringBean.testBean(TestSpringBean.java:21)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

说是这个bean没有被注释。没有动为啥出现这样的情况。根本就没有加载Bean。这个问题有待解决。