javaweb程序一登陆就出错，无法跳转到另一个页面

全是错误报告，不知道哪里出来问题，登陆之后应该跳转到下一个页面的结果也没有跳转，刚学要写课设，级求大神解决

严重: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.jsp.admin_jsp._jspService(admin_jsp.java:156)
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:292)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at filter.EncodingFilter2.doFilter(EncodingFilter2.java:39)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:716)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
at servlet.Login.doGet(Login.java:36)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at filter.EncodingFilter2.doFilter(EncodingFilter2.java:39)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
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:620)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2527)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2516)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
org.apache.jasper.JasperException: An exception occurred processing JSP page /admin.jsp at line 35

32: %>
33: 34: function confirmapply(){ 35: document.getElementById("showFrame").src="confirm.jsp?dno=<%=worker.getDno()%>&eno=<%=worker.getEno()%>"; 36: } 37: function dnoworker(){ 38: document.getElementById("showFrame").src="dnoworkers.jsp?dno=<%=worker.getDno()%>"; Stacktrace: at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:579) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476) 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:292) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at filter.EncodingFilter2.doFilter(EncodingFilter2.java:39) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:716) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318) at servlet.Login.doGet(Login.java:36) at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at filter.EncodingFilter2.doFilter(EncodingFilter2.java:39) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504) 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:620) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2527) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2516) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.NullPointerException at org.apache.jsp.admin_jsp._jspService(admin_jsp.java:156) 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) ... 42 more

java.lang.NullPointerException空指针问题从错误报告自上到下找到你自己写的类就可以找到错误

public class Login extends HttpServlet{
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
String uno=request.getParameter("account");
String pwd=request.getParameter("password");//password
String id=request.getParameter("id");//id
Service w=new Service();
try {
if(w.login(uno,id)!=null)
{
if(w.login(uno,id).getPassword().trim().equals(pwd))
{
System.out.println("登录成功");
if(id.equals("worker")){
request.setAttribute("uno",uno);
ServletContext application=this.getServletContext();
RequestDispatcher rd=application.getRequestDispatcher("/worker.jsp");
rd.forward(request, response);
}
else
{
request.setAttribute("uno",uno);
ServletContext application=this.getServletContext();
RequestDispatcher rd=application.getRequestDispatcher("/admin.jsp");
rd.forward(request, response);
}
}

                loginservlet的代码

你看看是不是你要跳转的页面路径写错了？？我以前就犯过类似的错误的

at servlet.Login.doGet(Login.java:36) 这行取得值应该是空的 debug模式打断点看下

可以将你的错误截个图发出来吗？

看看你是否有获取request重定向或者转发的时候错误

你看看你的类有没有被实例化

是你的admin.jsp里报的错, 找到那个编译生成的admin_jsp.java,

看156行有什么问题

1.新手在开发过程中要先了解一些会常遇到的异常种类，这样遇到问题了首先清楚是怎么回事了，才能对症下药。
可以参考：
2.知道是什么异常了（java.lang.NullPointerException 空指针异常），就可以在刚才运行的方法中在执行的第一步打断点一步一步排查下去问题应该就能找到了。如果还是找不到可以在下面的错误日志中查找看问题是出在哪个类的哪个方法中（如图中的 at servlet.Login.doGet(Login.java:36) ，这一行就说明你的Login中的doGet方法的第36行报空指针）。

以上是个人的一点建议，希望可以帮助你在以后的开发中能够及时定位到问题，解决问题。

异常参考：https://www.cnblogs.com/cvst/p/5822373.html

你这是空指针了，
你去java1234.com看看吧，这里面有毕业设计的例子

你重写了init()方法？就是写了init(ServletConfig config)这个？

页面应该跳的是500错误吧，你看一下admin.jsp里边，有一个变量你应该是接受并转型了，但这个值没接收到。图片说明

空指针了，有没实例化的变量在使用。

第一行错误就说了空异常了。

报错信息提示，你的前端页面出现空指针，你可以根据错误信息去定位，要学会debug啊

先看下是不是从service跳到admin.jsp的35那里写错了，如果不是，调试跳到程序中看下是不是service哪里写错了。

图片说明
admin.jsp调用java代码了，能贴出来看看嘛

密码和账号参数值没有接受到，或者没有account 和password 这两个参数

图片说明

你看看是不是你要跳转的页面路径写错了？？我以前就犯过类似的错误的