System.out.println（）在Java中有副作用嗎？

當我將println（）放入DAO方法中時，程序在我調用update方法時工作。System.out.println（）在Java中有副作用嗎？

@Override 
public Post getPostById(int id) { 
    Session session = DatabaseConnection.connect().openSession(); 
    Post post = (Post) session.load(Post.class, new Integer(id)); 
    System.out.println("debug " + post); 
    session.close(); 
    return post; 
}

當我不這樣做，它給了我一個錯誤

@Override 
public Post getPostById(int id) { 
    Session session = DatabaseConnection.connect().openSession(); 
    Post post = (Post) session.load(Post.class, new Integer(id)); 

    session.close(); 
    return post; 
}

這裏的錯誤信息：

SEVERE: Invalid property 'account' of bean class [com.personal.pojo.Post_$$_jvsta3d_0]: Getter for property 'account' threw exception; nested exception is java.lang.reflect.InvocationTargetException 
org.springframework.beans.InvalidPropertyException: Invalid property 'account' of bean class [com.personal.pojo.Post_$$_jvsta3d_0]: Getter for property 'account' threw exception; nested exception is java.lang.reflect.InvocationTargetException 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:704) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getNestedPropertyAccessor(AbstractNestablePropertyAccessor.java:836) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyAccessorForPropertyPath(AbstractNestablePropertyAccessor.java:813) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:608) 
    at org.springframework.validation.AbstractPropertyBindingResult.getActualFieldValue(AbstractPropertyBindingResult.java:99) 
    at org.springframework.validation.AbstractBindingResult.getFieldValue(AbstractBindingResult.java:229) 
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:120) 
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168) 
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188) 
    at org.springframework.web.servlet.tags.form.LabelTag.autogenerateFor(LabelTag.java:130) 
    at org.springframework.web.servlet.tags.form.LabelTag.resolveFor(LabelTag.java:120) 
    at org.springframework.web.servlet.tags.form.LabelTag.writeTagContent(LabelTag.java:90) 
    at org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:84) 
    at org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80) 
    at org.apache.jsp.WEB_002dINF.jsp.edit_jsp._jspx_meth_form_005flabel_005f0(edit_jsp.java:278) 
    at org.apache.jsp.WEB_002dINF.jsp.edit_jsp._jspx_meth_form_005fform_005f0(edit_jsp.java:193) 
    at org.apache.jsp.WEB_002dINF.jsp.edit_jsp._jspService(edit_jsp.java:144) 
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438) 
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) 
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 
    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.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:719) 
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:465) 
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:390) 
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:317) 
    at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168) 
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303) 
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1243) 
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1027) 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971) 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) 
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:860) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 
    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.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:316) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:122) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:48) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:205) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213) 
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176) 
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346) 
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262) 
    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:212) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:521) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:674) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Unknown Source) 
Caused by: java.lang.reflect.InvocationTargetException 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at org.springframework.beans.BeanWrapperImpl$BeanPropertyHandler.getValue(BeanWrapperImpl.java:307) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:622) 
    ... 95 more 
Caused by: org.hibernate.LazyInitializationException: could not initialize proxy - no Session 
    at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:165) 
    at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:286) 
    at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185) 
    at com.personal.pojo.Post_$$_jvsta3d_0.getAccount(Post_$$_jvsta3d_0.java) 
    ... 101 more 

Dec 31, 2015 7:03:28 PM org.apache.catalina.core.ApplicationDispatcher invoke 
SEVERE: Servlet.service() for servlet jsp threw exception 
org.hibernate.LazyInitializationException: could not initialize proxy - no Session 
    at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:165) 
    at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:286) 
    at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185) 
    at com.personal.pojo.Post_$$_jvsta3d_0.getAccount(Post_$$_jvsta3d_0.java) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at org.springframework.beans.BeanWrapperImpl$BeanPropertyHandler.getValue(BeanWrapperImpl.java:307) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:622) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getNestedPropertyAccessor(AbstractNestablePropertyAccessor.java:836) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyAccessorForPropertyPath(AbstractNestablePropertyAccessor.java:813) 
    at org.springframework.beans.AbstractNestablePropertyAccessor.getPropertyValue(AbstractNestablePropertyAccessor.java:608) 
    at org.springframework.validation.AbstractPropertyBindingResult.getActualFieldValue(AbstractPropertyBindingResult.java:99) 
    at org.springframework.validation.AbstractBindingResult.getFieldValue(AbstractBindingResult.java:229) 
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:120) 
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168) 
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188) 
    at org.springframework.web.servlet.tags.form.LabelTag.autogenerateFor(LabelTag.java:130) 
    at org.springframework.web.servlet.tags.form.LabelTag.resolveFor(LabelTag.java:120) 
    at org.springframework.web.servlet.tags.form.LabelTag.writeTagContent(LabelTag.java:90) 
    at org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:84) 
    at org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80) 
    at org.apache.jsp.WEB_002dINF.jsp.edit_jsp._jspx_meth_form_005flabel_005f0(edit_jsp.java:278) 
    at org.apache.jsp.WEB_002dINF.jsp.edit_jsp._jspx_meth_form_005fform_005f0(edit_jsp.java:193) 
    at org.apache.jsp.WEB_002dINF.jsp.edit_jsp._jspService(edit_jsp.java:144) 
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438) 
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) 
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 
    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.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:719) 
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:465) 
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:390) 
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:317) 
    at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168) 
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303) 
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1243) 
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1027) 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971) 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) 
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:860) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 
    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.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:316) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:122) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:48) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:205) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213) 
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176) 
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346) 
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:521) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:674) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Unknown Source)

這裏的我打電話的方法：

@RequestMapping("/edit/{id}") 
public String editPost(@PathVariable("id") int id, Model model) 
{ 
    model.addAttribute("post", RegistryDAO.getPostDAO().getPostById(id)); 
    return "edit"; 
}

這怎麼可能？

來源

2016-01-01 jarvan

的問題是與所生成的吸氣劑，並沒有表現出什麼造成了COMPLETE堆棧跟蹤'InvocationTargetException'就不可能進一步解決 –

好的，我固定它 – jarvan

可能重複：。HTTP：//計算器問題/ 21574236 /組織 - 代理http://stackoverflow.com/questions/19361963/error-org-hibernate-lazyinitializationexception-could-not-initialize-proxy- n http://stackoverflow.com/q/7654818/18157 –

System.out.println（）在Java中有副作用嗎？

是的。一個副作用是它產生輸出！

但更重要的是（在你的情況下）它可以改變計時和線程調度。如果在代碼的其他地方有一個併發錯誤，println可以防止錯誤發生。

錯誤消息不是很豐富，但它似乎是說某些對象（bean）具有account屬性，並且getter失敗。如果你能得到完整的異常棧跟蹤（例如從日誌文件），那麼應該有更多的線索。

這是（已添加從堆棧跟蹤）的根異常消息：

Caused by: org.hibernate.LazyInitializationException: 
    could not initialize proxy - no Session

吉姆警備已確定了一些基於該消息可能重複的;見上面的評論。先檢查那些。

莫非session.close（）; getPostById裏面會提前關閉會話嗎？

是的，它可能是。您需要在處理（打開和關閉）會話的過程中保持一致。

請注意，如果您「緩存」使用短期Session創建的對象，那麼當Session關閉時它們會斷開連接。如果對象被初始化，這可能會導致問題。我發現這個解釋（在Altassian documentation）：

Hibernate的會話

會話是一個Hibernate構建體用於介導與數據庫的連接。

會話在創建時會打開單個數據庫連接，並保留到會話關閉之前。 Hibernate從數據庫加載的每個對象都與會話相關聯，允許Hibernate自動保存修改的對象，並允許Hibernate實現諸如延遲加載等功能。

斷開連接的對象

如果一個對象被從其會話逐出（例如通過一個明確的，見下文），或在該對象是否仍然保持有效的會話被關閉，該對象是「斷開」來自會議。只要您不需要執行任何需要返回數據庫的操作（例如訪問延遲加載的集合），斷開連接的對象就會繼續工作。

如果您看到LazyInitializationException，這意味着Hibernate管理的對象的活期比其會話更長。

管理對象在會話之間不可移植。嘗試在一個會話中加載對象，然後將其保存到另一個會話中也會導致錯誤。（您可以使用Session.load（）或Session.get（）將對象重新引入新會話，但是要解決造成您嘗試在會話之間移動對象的任何問題。

來源

2016-01-01 00:46:14

難道是session.close（）; getPostById裏面會提前關閉會話嗎？ – jarvan

我不知道，爲什麼你會稱它爲「過早」。當session.close（）被調用時，會話關閉。所以，如果你不想這樣做，請刪除該方法調用。 – dunni

嗯，對，但是我應該把它打開，還是有比這更好的解決方案？ – jarvan

System.out.println（）在Java中有副作用嗎？

回答

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