Exception handling --- suggestion for improvements ---- (e.g., template tag masks original exception) correction in sample code

[Rick Hightower <ri...@eblox.com>]

We have been using struts for a good while. We really dig the framework,
but...

Often times the struts tags catch the original exception (e.g.,
ClassCastException), and then throw a JspException; thus, losing the
original stack trace. This hides\masks the original exception. Hiding the
orginal stack trace makes it harder to debug the problem.

I wrote a JSPWrapperException that preserves the orginal stack trace for
debugging.
JSPWrapperException extends JspWrapper; however, like ServletException, it
captures the original stack trace and displays it for debugging, i.e., the
JSPWrapperException prints out the original stack trace of the original
exception. This is a real boon for debugging.

I modified 50 or so files in our copy of the struts code base (a 1.0
derivative with some bug fixes and extra error handing) to use the
JSPWrapperException instead of the JspException.

It cost about an hour to make the changes, but I feel it will save us hours
of debugging in the future.

There is an ant build file with struts so making the changes and creating
struts.jar was easy.



I search the struts code base for code like this.... (example code)

try{
}
catch(XYZException e){
	throw new JspException(e.getMessage());
}

to code that looks like this
try{
}
catch(XYZException e){
	throw new JspWrapperException(e, e.getMessage());
}


BTW Here is the code for JspWrapperException....

Enjoy.....

/*
 * JspWrapperException.java
 *
 * Created on November 15, 2001, 11:14 PM
 */

package org.apache.struts.util;
import javax.servlet.jsp.JspException;

/**
 *
 * @author  rick
 */
public class JspWrapperException extends JspException  {

        Exception e;

    /**
     * @param     Exception e
     * @param     String message
     */
    public JspWrapperException(Exception e, String message) {
        super(message);
        this.e = e;
    }

    /**
     */
    public void printStackTrace () {
        super.printStackTrace();
        String sep = System.getProperty("line.separator", "\r\n");
        if (e != null) {
            System.err.println("--------------- extended Exception
nest ----------- ");
            e.printStackTrace();
        }
    }

    /**
     * @param ps
     */
    public void printStackTrace (java.io.PrintStream ps) {
        super.printStackTrace(ps);
        String sep = System.getProperty("line.separator", "\r\n");
        if (e != null) {
            ps.println("--------------- extended Exception nest -----------
");
            e.printStackTrace(ps);
        }
    }

    /**
     * @param pw
     */
    public void printStackTrace (java.io.PrintWriter pw) {
        super.printStackTrace(pw);
        String sep = System.getProperty("line.separator", "\r\n");
            //
            //Nested exception
        if (e != null) {
            pw.println("--------------- extended Exception nest -----------
");
            e.printStackTrace(pw);
        }
    }

    /**
     * @return
     */
    public String getMessage () {
        StringBuffer message = new StringBuffer(150);
        message.append(super.getMessage());

            //
            //add Line separator
        String sep = System.getProperty("line.separator", "\r\n");
        message.append(sep);

            //
            //Add the nested exception
        if (e != null) {
            message.append(e.getMessage());
            //char = props["line.separator"]
        }
        return  message.toString();
    }
}



Rick Hightower
Director of Development
eBlox, Inc.

Check out our new website!
www.eblox.com

Contact Info:
eBlox Tucson
phone: 520-615-9345 x103
fax: 520-529-5774

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