1.@Autowired和@Resource都可以用来装配bean，都可以写在字段上，或者方法上
2.@Autowired属于Spring的；@Resource为JSR-250标准的注释，属于J2EE的
3.@Autowired默认按类型装配，默认情况下必须要求依赖对象必须存在，如果要允许null值，可以设置它的required属性为false，例如：@Autowired(required=false)
，如果我们想使用名称装配可以结合@Qualifier注解进行使用，如下：
@Autowired()
@Qualifier("baseDao")
private BaseDao baseDao;
4.@Resource，默认安装名称进行装配，名称可以通过name属性进行指定，如果没有指定name属性，当注解写在字段上时，默认取字段名进行安装名称查找，如果注解写在setter方法上默认取属性名进行装配。当找不到与名称匹配的bean时才按照类型进行装配。但是需要注意的是，如果name属性一旦指定，就只会按照名称进行装配。
例如：
@Resource(name="baseDao")
private BaseDao baseDao;
推荐使用：@Resource注解在字段上，这样就不用写setter方法了，并且这个注解是属于J2EE的，减少了与spring的耦合。这样代码看起就比较优雅。
@Resource与@Autowired注解的区别
一、@Resource和@Autowired对比
@Resource默认按照名称方式进行bean匹配，
@Resource(import javax.annotation.Resource;)是J2EE的注解，
@Autowired默认按照类型方式进行bean匹配
@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(AbstractAutowireCapableBeanFact
ory.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;
}
Spring5：@Autowired注解、@Resource注解和@Service注解
https://www.cnblogs.com/szlbm/p/5512931.html
Spring注解@Resource和@Autowired区别对比
https://www.cnblogs.com/think-in-java/p/5474740.html
@Autowired 与@Resource的区别（详细）
https://blog.csdn.net/weixin_40423597/article/details/80643990