Spring Boot Autowire 自己的类答案

【问题标题】：Spring Boot Autowire own classSpring Boot Autowire 自己的类
【发布时间】：2016-12-14 11:40:03
【问题描述】：

由于它的名称，我无法自动装配我自己的类。我创建了一个MailSender 来通过JavaMailSender 发送邮件。

@Service
public class MailSender {

    @Autowired
    private JavaMailSender javaMailSender;

    public void send(File file) throws MailSendingException {
        // send my mail
    }

}

如果我尝试在我的控制器中使用 MailSender 和 @Autowired private MailSender mailSender;，我会收到以下消息：

my.app.controller.MyController 中的字段 mailSender 需要一个无法找到的“my.app.mail.MailSender”类型的 bean。

日志：

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.4.2.RELEASE)

14-Dec-2016 12:17:45.724 SEVERE [http-nio-8084-exec-34] org.apache.catalina.core.ContainerBase.addChildInternal ContainerBase.addChild: start: 
 org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/my-app]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:726)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:702)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:697)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:579)
    at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:455)
    at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1554)
    at sun.reflect.GeneratedMethodAccessor170.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at org.apache.catalina.manager.ManagerServlet.check(ManagerServlet.java:1428)
    at org.apache.catalina.manager.ManagerServlet.deploy(ManagerServlet.java:885)
    at org.apache.catalina.manager.ManagerServlet.doGet(ManagerServlet.java:343)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:301)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:108)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:615)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:136)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:74)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1015)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:652)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1575)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1533)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'myController': Unsatisfied dependency expressed through field 'mailSender'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'my.app.mail.MailSender' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:592)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:370)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1219)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:551)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:754)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:761)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:371)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at org.springframework.boot.web.support.SpringBootServletInitializer.run(SpringBootServletInitializer.java:151)
    at org.springframework.boot.web.support.SpringBootServletInitializer.createRootApplicationContext(SpringBootServletInitializer.java:131)
    at org.springframework.boot.web.support.SpringBootServletInitializer.onStartup(SpringBootServletInitializer.java:86)
    at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:169)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5147)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 44 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'my.app.mail.MailSender' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1466)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1097)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1059)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:589)
    ... 66 more

@ComponentScan({"my.app"}) 有效，因为其他类已正确自动装配。

现在，如果我在 MailSender2 或 MailService 中重命名类 MailSender，它会按预期工作。

为什么 Spring Boot (1.4.2.RELEASE) 不能自动装配这个类？名称MailSender 是不能用于自动连线的保留名称吗？

【问题讨论】：

S.B启动时您没有记录与问题相关的信息？
在上面添加了登录帖子。
Spring Boot 默认注册JavaMailSender，它使用名称mailSender 创建。由于您有一个名为MailSender 的类，因此派生的bean 名称是mailSender，它与自动配置的邮件发送器冲突。只需在@Service 中明确输入名称，例如@Service("myMailSender")。
很奇怪。您没有关于重复 bean id 的错误。如果您使用 S.B actuator，我建议您浏览 /beans 服务并搜索 id 为 mailSender 的 bean 是否存在。如果是这样，你就有答案了。
@M. Deinum，你有参考吗？我很感兴趣。在我找到的文档（docs.spring.io/spring/docs/current/spring-framework-reference/… 和 docs.spring.io/spring/docs/4.3.4.RELEASE/…）上没有明确说明。

标签： java spring-boot autowired

【解决方案1】：

在您的控制器中尝试删除import org.springframework.mail.MailSender 或等效导入，这些导入导入除您尝试自动装配的邮件之外的任何其他 MailSender。只需导入您自己的 MailSender，自动装配就可以按预期工作。如果没有，你可以看看@Qualifier注解。

【讨论】：

【解决方案2】：

在您的服务中使用限定符，如下所示：

@Service
@Qualifier("springBootMailService")

【讨论】：