为什么servlet会抛出这个servlet .service()异常?

Question

我使用Netbeans。当运行从会话bean调用方法的servlet时，我得到了以下异常:

ApplicationDispatcher[/TheLibrarySystem-war] PWC1231: Servlet.service() for servlet       ListReservations threw exception
java.lang.NullPointerException
    at org.apache.jsp.ListReservations_jsp._jspService(ListReservations_jsp.java from   :68)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:389)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:486)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:380)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
    at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:427)
    at org.apache.catalina.core.ApplicationDispatcher.doInvoke(ApplicationDispatcher.java:873)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:723)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:558)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:456)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:382)
    at servlet.TheLibrarySystemServlet.processRequest(TheLibrarySystemServlet.java:86)
    at servlet.TheLibrarySystemServlet.doGet(TheLibrarySystemServlet.java:185)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
    at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:427)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:315)
    at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:287)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:218)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:94)
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:98)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:222)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
    at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1093)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:166)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
    at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1093)
    at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:291)
    at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:666)
    at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:597)
    at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:872)
    at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:341)
    at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:263)
    at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:214)
    at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:264)
    at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)
PWC1412: WebModule[/TheLibrarySystem-war] ServletContext.log():TheLibrarySystemServlet: Exception in TheLibrarySystemServlet.processRequest()

会话bean中的方法显然工作良好，并将正确的值返回给servlet端。

代码在:调度员。提出(请求、响应);

谷歌周围，似乎这不是一个代码问题，任何想法是什么导致它和如何解决?

Answer 1

通常在存在类路径错误时出现此异常。请检查您的构建路径。它不应该包含jsp-api*.jar。如有，请删除