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java.lang.NullPointerException 老是出现这个错误怎么回事？
java.lang.NullPointerException 老是出现这个错误怎么回事？
09-09-08 & 发布
一直察看是否server端有消息传入,当没有消息传入的时候这句is = socket.getInputStream();is就为null,所以在初始化br的时候br = new BufferedReader(new InputStreamReader(is,&DB2312&)); br也为空.string= br.readLine(); 这里你调用了br的方法,因为br是null,所以出现空指向异常
请登录后再发表评论!出现java.lang.NullPointerException这个错误，网页登陆时。出现java.lang.NullPointerExcepti-知识宝库
你可能对下面的信息感兴趣查看:8357|回复：13
public List search(Class cls,List&String[]& lis,int begin,int size){
& && &&&String className=cls.getName();
& && &&&Session session=sessionFactory.getCurrentSession();
& && &&&StringBuffer hql=new StringBuffer(&from &+className+& objcls where 1=1&);
& && &&&hql.append(createHQL( lis));
& && &&&System.out.println(hql);
& && &&&Query query=session.createQuery(hql.toString());
& && &&&query.setFirstResult(begin);
& && &&&query.setMaxResults(size);
& && &&&List returnlis=query.list();
运行到：List returnlis=query.list();时
出现：java.lang.NullPointerException异常
我用的数据库是mysql
我的表里有俩个外键：
& & 如何解决？
trade_ibfk_1& & & & releaId& & & & huanmie& & & & user_info& & & & User_Id& & & & SET NULL& & & & CASCADE& & & &
trade_ibfk_2& & & & buyId& & & & huanmie& & & & user_info& & & & User_Id& & & & SET NULL& & & & CASCADE& & & &
都是关联user_info表的主键
中级工程师
Just do it
是分页的么？那语句真心不是很懂，classname后面的是什么- -！
11:23:50 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet default threw exception
java.lang.NullPointerException
& & & & at org.hibernate.persister.entity.AbstractEntityPersister.loadByUniqueKey(AbstractEntityPersister.java:1672)
& & & & at org.hibernate.type.EntityType.loadByUniqueKey(EntityType.java:641)
& & & & at org.hibernate.type.EntityType.resolve(EntityType.java:415)
& & & & at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139)
& & & & at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:877)
& & & & at org.hibernate.loader.Loader.doQuery(Loader.java:752)
& & & & at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
& & & & at org.hibernate.loader.Loader.loadEntity(Loader.java:1881)
& & & & at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:71)
& & & & at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:65)
& & & & at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3072)
& & & & at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:434)
& & & & at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:415)
& & & & at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:165)
& & & & at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:223)
& & & & at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:126)
& & & & at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:905)
& & & & at org.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:873)
& & & & at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:590)
& & & & at org.hibernate.type.EntityType.resolve(EntityType.java:412)
& & & & at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139)
& & & & at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:877)
& & & & at org.hibernate.loader.Loader.doQuery(Loader.java:752)
& & & & at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
& & & & at org.hibernate.loader.Loader.doList(Loader.java:2228)
& & & & at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2125)
& & & & at org.hibernate.loader.Loader.list(Loader.java:2120)
& & & & at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
& & & & at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:361)
& & & & at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
& & & & at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1148)
& & & & at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
& & & & at com.huanmie.tools.dao.BaseDao.search(BaseDao.java:80)
& & & & at com.huanmie.tools.dao.impl.TradeDaoImpl.selectTrade(TradeDaoImpl.java:92)
& & & & at com.huanmie.tools.service.impl.TradeServiceImpl.selectTrade(TradeServiceImpl.java:35)
& & & & at com.huanmie.tools.service.impl.TradeServiceImpl$$FastClassByCGLIB$$bbf7a807.invoke(&generated&)
& & & & at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
& & & & at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:700)
& & & & at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
& & & & at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
& & & & at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
& & & & at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
& & & & at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
& & & & at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:635)
& & & & at com.huanmie.tools.service.impl.TradeServiceImpl$$EnhancerByCGLIB$$43167f12.selectTrade(&generated&)
& & & & at com.huanmie.tools.action.TradeAction.selectTrade(TradeAction.java:24)
& & & & at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
& & & & at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
& & & & at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
& & & & at java.lang.reflect.Method.invoke(Method.java:597)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:267)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:229)
& & & & at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:221)
& & & & at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:150)
& & & & at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:48)
& & & & at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:123)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:184)
& & & & at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:105)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:83)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:207)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:74)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:127)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:107)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:206)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:115)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:143)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:121)
& & & & at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:170)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:123)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
& & & & at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
& & & & at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
& & & & at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:50)
& & & & at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:504)
& & & & at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:422)
& & & & at com.huanmie.tools.filter.MyStrutsFilterDispatcher.doFilter(MyStrutsFilterDispatcher.java:50)
& & & & at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
& & & & at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
& & & & at com.huanmie.tools.util.AuthorityFilter.doFilter(AuthorityFilter.java:86)
& & & & at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
& & & & at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
& & & & at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
& & & & at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
& & & & at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
& & & & at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
& & & & at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
& & & & at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
& & & & at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
& & & & at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
& & & & at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
& & & & at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
& & & & at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
& & & & at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
& & & & at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
& & & & at java.lang.Thread.run(Thread.java:662)
className是得到类名
就是hql语句：from Table(表名)
表名Table就是类名 className
本帖最后由 huang丶xz 于
11:31 编辑
是hql语句：from Table
小洋(on my way)
查询不到结果。。。。建议楼主把完整代码贴出来，我看了半天也不知道你想查询什么！
51CTOjava板块讨论QQ群：【1000人群】2群：【可加】 & && && &欢迎热爱JAVA的来讨论^_^
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我又从头做一遍，重建表，查询没问题
但是，我本来建的俩个外键，变成四个了，然后删除多出来的，又报这个错误
我怀疑是外键的问题
我用的是mysql数据库，工具是：Navicat 8
这个怎么解决啊？
中级工程师
Just do it
引用:原帖由 huang丶xz 于
11:29 发表
是hql语句：from Table className后面的objcls是什么意思吖？
见识短了，没有见过- -！
不会是as xxx这个吧？
还有你输出的hql里面的className正确么？外键问题的话，应该是不存在问题吧？你都是hql喔。
都是实体类来查找字段的。
本帖最后由 davenzeng 于
17:49 编辑
className后面的objcls就是你说的意思
Session session=sessionFactory.getCurrentSession();
& & & & & & & & StringBuffer hql=new StringBuffer(&from Trade&);
& & & & & & & &
& & & & & & & & System.out.println(hql);
& & & & & & & & Query query=session.createQuery(hql.toString());
& & & & & & & &
& & & & & & & & query.setFirstResult(begin);
& & & & & & & & query.setMaxResults(size);
& & & & & & & & List returnlis=query.list();
& & & & & & & &
我这样写也出现这个问题
运行到这部List returnlis=query.list();出现的这个错
中级工程师
Just do it
引用:原帖由 huang丶xz 于
18:18 发表
Session session=sessionFactory.getCurrentSession();
StringBuffer hql=new StringBuffer(&from Trade&);
System.out.println(hql);
Query query=session.createQuery(hql.toString());
query.setFi ... 你是想实现分页呢还是需要怎么样吖？下班了，明天帮你看下。
分页的话很简单的。}