@Resource与@Autowired注解的区别

水深无声 2022-04-08 14:25 258阅读 0赞

**一、区别**

1、**@Resource**默认按照名称方式进行bean匹配，**@Autowired**默认按照类型方式进行bean匹配

2、**@Resource**(import javax.annotation.Resource;)是J2EE的注解，**@Autowired**(import                                     org.springframework.beans.factory.annotation.Autowired;)是Spring的注解

Spring属于第三方的，J2EE是Java自己的东西。使用@Resource可以减少代码和Spring之间的耦合。

**二、@Resource注入**

现在有一个接口Human和两个实现类ManImpl、WomanImpl，在service层的一个bean中要引用了接口Human，这种情况处理如下：

接口Human

package testwebapp.com.wangzuojia.service;
     
    public interface Human {
        
        public void speak();
        
        public void walk();
    }

实现类ManImpl

package testwebapp.com.wangzuojia.service.impl;
     
    import org.springframework.stereotype.Service;
     
    import testwebapp.com.wangzuojia.service.Human;
     
    @Service
    public class ManImpl implements Human {
     
    	public void speak() {
    		System.out.println(" man speaking!");
     
    	}
     
    	public void walk() {
    		System.out.println(" man walking!");
     
    	}
     
    }

实现类WomanImpl

package testwebapp.com.wangzuojia.service.impl;
     
    import org.springframework.stereotype.Service;
     
    import testwebapp.com.wangzuojia.service.Human;
     
    @Service
    public class WomanImpl implements Human {
     
    	public void speak() {
    		System.out.println(" woman speaking!");
     
    	}
     
    	public void walk() {
    		System.out.println(" woman walking!");
     
    	}
     
    }

主调类SequenceServiceImpl

package testwebapp.com.wangzuojia.service.impl;
     
    import java.util.Map;
     
    import javax.annotation.Resource;
     
    import org.springframework.stereotype.Service;
     
    import testwebapp.com.wangzuojia.dao.SequenceMapper;
    import testwebapp.com.wangzuojia.service.Human;
    import testwebapp.com.wangzuojia.service.SequenceService;
     
    @Service
    public class SequenceServiceImpl implements SequenceService {
     
    	@Resource
    	private SequenceMapper sequenceMapper;
    	public void generateId(Map<String, String> map) {
    		sequenceMapper.generateId(map);
    		
    	}
    	//起服务此处会报错
    	@Resource
    	private Human human;
     
    }

这时候启动tomcat会包如下错误：

严重: Exception sendingcontext initialized event to listener instance of classorg.springframework.web.context.ContextLoaderListenerorg.springframework.beans.factory.BeanCreationException: Error creating beanwith name 'sequenceServiceImpl': Injection of resource dependencies failed;nested exception isorg.springframework.beans.factory.NoUniqueBeanDefinitionException: Noqualifying bean of type \[testwebapp.com.wangzuojia.service.Human\] is defined:expected single matching beanbut found 2: manImpl,womanImpl atorg.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:311) atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214) atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543) atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) atorg.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) atorg.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) atorg.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) atorg.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) atorg.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772) atorg.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:838) atorg.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:537) atorg.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:446) atorg.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:328) atorg.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107) atorg.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4717) atorg.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5179)atorg.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) atorg.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1404) atorg.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1394) atjava.util.concurrent.FutureTask.run(FutureTask.java:266) atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)atjava.lang.Thread.run(Thread.java:745) Caused by:org.springframework.beans.factory.NoUniqueBeanDefinitionException: Noqualifying bean of type \[testwebapp.com.wangzuojia.service.Human\] is defined: expectedsingle matching bean but found 2: manImpl,womanImpl atorg.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1126) atorg.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014) atorg.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:508) atorg.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:486) atorg.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:615) atorg.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:169) atorg.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) atorg.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:308) ...22 more

报错的地方给我们提示了:but found 2: manImpl,womanImpl      意思是Human有两个实现类。解决方案如下：

package testwebapp.com.wangzuojia.service.impl;
     
    import java.util.Map;
     
    import javax.annotation.Resource;
     
    import org.springframework.stereotype.Service;
     
    import testwebapp.com.wangzuojia.dao.SequenceMapper;
    import testwebapp.com.wangzuojia.service.Human;
    import testwebapp.com.wangzuojia.service.SequenceService;
     
    @Service
    public class SequenceServiceImpl implements SequenceService {
     
    	@Resource
    	private SequenceMapper sequenceMapper;
    	public void generateId(Map<String, String> map) {
    		sequenceMapper.generateId(map);
    		
    	}
    	
    	@Resource(name = "manImpl")//注意是manImpl不是ManImpl，因为使用@Service，容器为我们创建bean时默认类名首字母小写
    	private Human human;
     
    }

这样启动服务就不会报错了。如果是使用的@Autowired注解，要配上@Qualifier("manImpl")，代码如下：

package testwebapp.com.wangzuojia.service.impl;
     
    import java.util.Map;
     
    import javax.annotation.Resource;
     
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.stereotype.Service;
     
    import testwebapp.com.wangzuojia.dao.SequenceMapper;
    import testwebapp.com.wangzuojia.service.Human;
    import testwebapp.com.wangzuojia.service.SequenceService;
     
    @Service
    public class SequenceServiceImpl implements SequenceService {
     
    	@Resource
    	private SequenceMapper sequenceMapper;
    	public void generateId(Map<String, String> map) {
    		sequenceMapper.generateId(map);
    		
    	}
    	
    	@Autowired
    	@Qualifier("manImpl")
    	private Human human;
     
    }

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以下作者信息

作者：wangzuojia001   
来源：CSDN   
原文：[https://blog.csdn.net/wangzuojia001/article/details/54312074 ][https_blog.csdn.net_wangzuojia001_article_details_54312074]

[https_blog.csdn.net_wangzuojia001_article_details_54312074]: https://blog.csdn.net/wangzuojia001/article/details/54312074%C2%A0