Hibernate中通过传入实体的主键id来使用get方法获取整个实体的内容问题

Bertha 。 2022-05-14 01:48 54阅读 0赞

做老项目的一个需求变更，遇到一个问题，我直接调用封装好的dao中的get方法，传入参数这个实体的主键，结果报下面的错误：

八月 31, 2018 11:14:49 上午 org.apache.catalina.core.StandardWrapperValve invoke
    严重: Servlet.service() for servlet [springServlet] in context with path [/JKGL2] threw exception [Request processing failed; nested exception is org.hibernate.MappingException: Unknown entity: java.lang.Object] with root cause
    org.hibernate.MappingException: Unknown entity: java.lang.Object
    	at org.hibernate.internal.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:1131)
    	at org.hibernate.internal.SessionImpl.locateEntityPersister(SessionImpl.java:2484)
    	at org.hibernate.internal.SessionImpl.access$1900(SessionImpl.java:174)
    	at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.<init>(SessionImpl.java:2426)
    	at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.<init>(SessionImpl.java:2430)
    	at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.<init>(SessionImpl.java:2417)
    	at org.hibernate.internal.SessionImpl.byId(SessionImpl.java:1064)
    	at org.hibernate.internal.SessionImpl.get(SessionImpl.java:987)
    	at com.wonders.ph.common.persistence.AbstractDao.get(AbstractDao.java:185)
    	at com.wonders.ph.jksite.modules.mg.service.MgUpdateYypbSelectService.queryData(MgUpdateYypbSelectService.java:39)
    	at com.wonders.ph.jksite.modules.mg.service.MgUpdateYypbSelectService$$FastClassByCGLIB$$2b6629d1.invoke(<generated>)
    	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
    	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
    	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
    	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
    	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    	at com.wonders.ph.jksite.modules.mg.service.MgUpdateYypbSelectService$$EnhancerByCGLIB$$877fe5d4.queryData(<generated>)
    	at com.wonders.ph.jksite.modules.mg.service.MgUpdateYypbSelectService$$FastClassByCGLIB$$2b6629d1.invoke(<generated>)
    	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
    	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
    	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
    	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
    	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:631)
    	at com.wonders.ph.jksite.modules.mg.service.MgUpdateYypbSelectService$$EnhancerByCGLIB$$a880b7aa.queryData(<generated>)
    	at com.wonders.ph.jksite.modules.mg.MgUpdateYypbSelectController.init(MgUpdateYypbSelectController.java:36)
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    	at java.lang.reflect.Method.invoke(Method.java:606)
    	at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at com.wonders.ph.jksite.modules.common.filter.XssFilter.doFilter(XssFilter.java:33)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
    	at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
    	at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
    	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    	at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
    	at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
    	at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
    	at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
    	at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
    	at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)
    	at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
    	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    	at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
    	at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at org.springframework.orm.hibernate4.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:149)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at org.springframework.orm.hibernate4.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:149)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
    	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1082)
    	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:623)
    	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    	at java.lang.Thread.run(Thread.java:744)

我原来代码是这样写的：

entity po = (entity)dao.get(id);

查了一下出错原因：  
（1）系统封装好的dao继承了basedao，而basedao的泛型类型为Objec  
（2）我直接传进去的是一个字符串id，也就是该实体的主键，但是看里层的代码，是`getSession().get(Entity.class,id);`，所以如果使用系统的dao，且只传字符串id，那么是无法识别该Entity，所以会报unknown Entity异常  
（3）上网查了一下，有的人说是配置文件，映射有问题，我检查了不存在问题；有人说是因为需要将那个值set到实体，传进去一个对象，我试了也不可以，还是报unknown Entity异常  
解决办法：  
我没有使用dao.get(id)的形式，如果要使用这个形式，那么dao应该是我自定义，不是使用系统封装好的dao，并且我定义dao需要继承basedao且泛型参数为我的对应实体，因为我一次需要操作三张表，所以我没有自定义DAO，还是使用封装好的，只不过使用方法有些区别：

dao.getSession.get(Entity.class,id);

这样的话就不再报unknown Entity的异常了。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70]: /images/20220514/b7d177219c654d9a8448847469787db1.png