How can I print error stack trace in JSP page?

Question

I have set my error page like this in web.xml:

 
  java.lang.Exception
  /erro         


        

Answer 1

Using JSP scriptlets is a frowned upon practice since a decade. You'd best avoid it.

If you're already on EL 2.2 or newer (Tomcat 7+, JBoss AS 6+, WildFly, GlassFish 3+, etc), with new support for method expressions of the form ${instance.method()}, then you can just use 100% EL for this.

First you need to explicitly flush the JSP writer via JspWriter#flush(), so that all preceding JSP template output really gets written to the writer of the servlet response:

${pageContext.out.flush()}

Then you can just pass ServletResponse#getWriter() to Throwable#printStackTrace().

${exception.printStackTrace(pageContext.response.writer)}

Complete example:

<%@page pageEncoding="UTF-8" isErrorPage="true" %>
...
${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}

If you're already on EL 3.0 (Tomcat 8+, WildFly, GlassFish 4+, etc), you can even make it a single expression with the new semicolon operator which separates EL statements:

<%@page pageEncoding="UTF-8" isErrorPage="true" %>
...
${pageContext.out.flush();exception.printStackTrace(pageContext.response.writer)}

If you can't use isErrorPage="true" for some reason (and thus ${exception} implicit object isn't available), then just substitute with ${requestScope['javax.servlet.error.exception']}:

<%@page pageEncoding="UTF-8" %>
...
${pageContext.out.flush()}${requestScope['javax.servlet.error.exception'].printStackTrace(pageContext.response.writer)}

If you're still not on EL 2.2, then your best bet is creating a custom EL function. Detail can be found in What is the good approach to forward the exception from servlets to a jsp page?

Below is a more complete error page example with more detail:

<%@page pageEncoding="UTF-8" isErrorPage="true" %>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
...

    
Exception: 
    
Exception type: 
    
Exception message: 
    
Request URI: 
    
Servlet name: 
    
Status code: 
    
Stack trace: 
${pageContext.out.flush()}${exception.printStackTrace(pageContext.response.writer)}