这个问题搞了很久了,问人也问过,上网也查过,还是解决不了。这是运行时报错的。
报错如下:希望可以帮我解决的加下QQ:335334696 给疑惑的我一个解答,谢谢达人们了~java.lang.NullPointerException
at com.rjh.util.SqlHelper.executeQuery(SqlHelper.java:141)
at com.rjh.service.UsersService.checkUser(UsersService.java:94)
at com.rjh.controller.LoginClServlet.doGet(LoginClServlet.java:39)
at com.rjh.controller.LoginClServlet.doPost(LoginClServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
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.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:859)
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)
2012-10-23 10:39:54 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet LoginClServlet threw exception
java.lang.RuntimeException
at com.rjh.util.SqlHelper.executeQuery(SqlHelper.java:149)
at com.rjh.service.UsersService.checkUser(UsersService.java:94)
at com.rjh.controller.LoginClServlet.doGet(LoginClServlet.java:39)
at com.rjh.controller.LoginClServlet.doPost(LoginClServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
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.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:859)
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)
报错如下:希望可以帮我解决的加下QQ:335334696 给疑惑的我一个解答,谢谢达人们了~java.lang.NullPointerException
at com.rjh.util.SqlHelper.executeQuery(SqlHelper.java:141)
at com.rjh.service.UsersService.checkUser(UsersService.java:94)
at com.rjh.controller.LoginClServlet.doGet(LoginClServlet.java:39)
at com.rjh.controller.LoginClServlet.doPost(LoginClServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
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.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:859)
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)
2012-10-23 10:39:54 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet LoginClServlet threw exception
java.lang.RuntimeException
at com.rjh.util.SqlHelper.executeQuery(SqlHelper.java:149)
at com.rjh.service.UsersService.checkUser(UsersService.java:94)
at com.rjh.controller.LoginClServlet.doGet(LoginClServlet.java:39)
at com.rjh.controller.LoginClServlet.doPost(LoginClServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
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.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:859)
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)
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at com.rjh.service.UsersService.checkUser(UsersService.java:94)
at com.rjh.controller.LoginClServlet.doGet(LoginClServlet.java:39)
at com.rjh.controller.LoginClServlet.doPost(LoginClServlet.java:57)
这几行,仔细看一下,NullPointerException 空指针异常,对象为NULL时调用了方法出现的异常
比如 String s = null;
s.length(); 该行报错
Person p = null;
p.getName(); 该行报错
这个原因就是值没有造成的