How to get the line number if exception occurs in jsp page

Question

I know that in a servlet or in a normal Java file we can get the line number where the exception occurred using the printstacktrace method.

But because a JSP is converted to a servlet, I was not able get the exception line number even by using printstacktrace method. Is there any way to get the line number (where exception occurred) of the JSP file when an exception occurs.

My JSP file:

Line Number:
17:        <%
18:            try {
19:                int a[] = new int[1];
20:                System.out.println(a[3]);
21:            } catch (Exception e) {
22:                e.printStackTrace();
23:            }
24:        %>

Here the exception is actually happening at line number 20, but when I run it, it is showing an exception at line number 77, which I don't even have in my file.

SEVERE:   java.lang.ArrayIndexOutOfBoundsException: 3
at org.apache.jsp.index_jsp._jspService(index_jsp.java:77)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:344)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.glassfish.tyrus.servlet.TyrusServletFilter.doFilter(TyrusServletFilter.java:253)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:428)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:316)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:744)

Because it is converting the jsp to a servlet, it is showing the line number as 77 instead of 20, but I just want it to print the line no as 20 (where exception was occurred) instead of 77, because in a larger file, I may find it difficult to locate where the exception was happening.

Answer 1

Every JSP is converted to a servlet on runtime, which means you should look for the generated servlet code. In Tomcat it is in the work/ folder, but to make sure, search for the index.jsp.java file in your servlet container's folder.

Answer 2

This and other problems made me reduce the Java code in JSP pages to the absolute minimum. I create helper objects for everything I need to do in a JSP page which contains the meat of the Java code (which means I can unit test this code as well).

The JSP then only contains the bare minimum:

<%Helper tool = new Helper();%>

<%=tool.foo()%>

Answer 3

Sometimes it's helpful to calculate the offset of the source line of the JSP file. E.g.:

System.out.println("Line 9: line number offset: " + (new Exception().getStackTrace()[0].getLineNumber() - 9));

Of course you need to place this block after each inlcude or JSP comment since they cause the offset to change.