TargetError.java

/**
 *
 * This file is a part of ZOOLA - an extensible BeanShell implementation.
 * Zoola is based on original BeanShell code created by Pat Niemeyer.
 *
 * Original BeanShell code is Copyright (C) 2000 Pat Niemeyer <pat@pat.net>.
 *
 * New portions are Copyright 2012 Rafal Lewczuk <rafal.lewczuk@jitlogic.com>
 *
 * This is free software. You can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * This software is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with ZOOLA. If not, see <http://www.gnu.org/licenses/>.
 *
 */


package bsh;

import bsh.ast.SimpleNode;

import java.lang.reflect.InvocationTargetException;

import java.io.PrintStream;

/**
	TargetError is an EvalError that wraps an exception thrown by the script	
	(or by code called from the script).  TargetErrors indicate exceptions 
	which can be caught within the script itself, whereas a general EvalError 
	indicates that the script cannot be evaluated further for some reason.
	
	If the exception is caught within the script it is automatically unwrapped,
	so the code looks like normal Java code.  If the TargetError is thrown
	from the eval() or interpreter.eval() method it may be caught and unwrapped
	to determine what exception was thrown.
*/
public final class TargetError extends EvalError 
{
	private final boolean inNativeCode;

	public TargetError(
		String msg, Throwable t, SimpleNode node, CallStack callstack,
		boolean inNativeCode )
	{
		super( msg, node, callstack, t );
		this.inNativeCode = inNativeCode;
	}

	public TargetError( Throwable t, SimpleNode node, CallStack callstack )
	{
		this("TargetError", t, node, callstack, false);
	}

	public Throwable getTarget()
	{
		// check for easy mistake
		Throwable target = getCause();
		if(target instanceof InvocationTargetException)
			return((InvocationTargetException)target).getTargetException();
		else
			return target;
	}

	public String getMessage() 
	{
		return super.getMessage() 
			+ "\nTarget exception: " + 
			printTargetError( getCause() );
	}

    public void printStackTrace( boolean debug, PrintStream out ) {
		if ( debug ) {
			super.printStackTrace( out );
			out.println("--- Target Stack Trace ---");
		}
		getCause().printStackTrace( out );
	}

	/**
		Generate a printable string showing the wrapped target exception.
		If the proxy mechanism is available, allow the extended print to
		check for UndeclaredThrowableException and print that embedded error.
	*/
	private String printTargetError( Throwable t ) 
	{
		return getCause().toString() + "\n" + xPrintTargetError( t );
	}

	/**
		Extended form of print target error.
		This indirection is used to print UndeclaredThrowableExceptions 
		which are possible when the proxy mechanism is available.

		We are shielded from compile problems by using a bsh script.
		This is acceptable here because we're not in a critical path...
		Otherwise we'd need yet another dynamically loaded module just for this.
	*/
	private String xPrintTargetError( Throwable t ) 
	{
		String getTarget =
			"import java.lang.reflect.UndeclaredThrowableException;"+
			"String result=\"\";"+
			"while ( target instanceof UndeclaredThrowableException ) {"+
			"	target=target.getUndeclaredThrowable(); " +
			"	result+=\"Nested: \"+target.toString();" +
			"}"+
			"return result;";
		Interpreter i = new Interpreter();
		try {
			i.set("target", t);
			return (String)i.eval( getTarget );
		} catch ( EvalError e ) {
			throw new InterpreterError("xprintarget: "+e.toString() );
		}
	}

	/**
		Return true if the TargetError was generated from native code.
		e.g. if the script called into a compiled java class which threw
		the excpetion.  We distinguish so that we can print the stack trace
		for the native code case... the stack trace would not be useful if
		the exception was generated by the script.  e.g. if the script
		explicitly threw an exception... (the stack trace would simply point
		to the bsh internals which generated the exception).
	*/
	public boolean inNativeCode() { 
		return inNativeCode; 
	}
}