详细错误：
1 严重: Context initialization failed 2 org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'studentController': Unsatisfied dependency expressed through field 'studentServiceImpl'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'studentServiceImpl': Unsatisfied dependency expressed through field 'studentDaoImpl'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'cn.mgy.dao.StudentDao' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} 3 at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) 4 at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) 5 at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) 6 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1268) 7 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) 8 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) 9 at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312) 10 at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) 11 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308) 12 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) 13 at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) 14 at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) 15 at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) 16 at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:668) 17 at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:634) 18 at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:682) 19 at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:553) 20 at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:494) 21 at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:171) 22 at javax.servlet.GenericServlet.init(GenericServlet.java:158) 23 at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1144) 24 at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1091) 25 at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:773) 26 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134) 27 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) 28 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) 29 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) 30 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) 31 at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650) 32 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) 33 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) 34 at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) 35 at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) 36 at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) 37 at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) 38 at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) 39 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) 40 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) 41 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 42 at java.lang.Thread.run(Thread.java:748)
解决方案：
public class StudentDaoImpl implements StudentDao 类忘记加 @Repository 注解，加上就可以解决问题了