空指针异常

Question

@RequestMapping("/transformer/recommend/transRecommendRankTag/add.do")
public void add(Model model) {
TransRecommendGroup recommendGroup = recommendRankTagBo.getById(TransRecommendGroup.class, 1L);
TransRecommendType recommendType = recommendGroup.getRecommendType();
CriteriaInfo ci = new CriteriaInfo();
ci.eq("recommendType", recommendType);
List<TransRecommendTypeEntity> recommendTypeEntityList = recommendRankTagBo.getEntitiesByCriteriaInfo(TransRecommendTypeEntity.class, ci);
model.addAttribute("recommendGroup", recommendGroup);
model.addAttribute("recommendTypeEntityList", recommendTypeEntityList);
出现的异常：
严重: Servlet.service() for servlet appServlet threw exception
java.lang.NullPointerException
at com.uusee.transformer.recommend.controller.TransRecommendRankTagController.add(TransRecommendRankTagController.java:112)
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 org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:175)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:421)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:409)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:774)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
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.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
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:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)

Answer 1

很可能是recommendGroup==null，没有id为1的记录
也可能是recommendRankTagBo==null
看报错在哪一行就知道了

Answer 2

TransRecommendRankTagController.java:112
这一行在哪？你都不注明哪一行出现的异常，那我们怎么找呢？

Answer 3

at com.uusee.transformer.recommend.controller.TransRecommendRankTagController.add(TransRecommendRankTagController.java:112)这个是你的代码 ？
如果是的话，就查查，为什么抛出空指针异常

Answer 4

楼主的代码里应该多些错误校验哦，别全是写void函数

Answer 5

recommendGroup 这个查找出来应该是NULL 所以出现空指针异常了。