fop/src/sandbox/org/apache/fop/render/afp/exceptions/NestedRuntimeException.java

/*
 * Copyright 2006 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* $Id$ */
package org.apache.fop.render.afp.exceptions;

import java.io.PrintStream;
import java.io.PrintWriter;

/**
 * Handy class for wrapping runtime Exceptions with a root cause.
 * This technique is no longer necessary in Java 1.4, which provides
 * built-in support for exception nesting. Thus exceptions in applications
 * written to use Java 1.4 need not extend this class.
 *
 */
public abstract class NestedRuntimeException extends RuntimeException {

	/** Root cause of this nested exception */
	private Throwable _underlyingException;

	/**
	 * Construct a <code>NestedRuntimeException</code> with the specified detail message.
	 * @param msg The detail message.
	 */
	public NestedRuntimeException(String msg) {
		super(msg);
	}

	/**
	 * Construct a <code>NestedRuntimeException</code> with the specified
	 * detail message and nested exception.
	 * @param msg The detail message.
	 * @param t The nested exception.
	 */
	public NestedRuntimeException(String msg, Throwable t) {
		super(msg);
		_underlyingException = t;

	}

	/**
	 * Gets the original triggering exception
	 * @return The original exception as a throwable.
	 */
	public Throwable getUnderlyingException() {

		return _underlyingException;

	}

	/**
	 * Return the detail message, including the message from the nested
	 * exception if there is one.
	 * @return The detail message.
	 */
	public String getMessage() {

		if (_underlyingException == null) {
			return super.getMessage();
		} else {
			return super.getMessage()
				+ "; nested exception is "
				+ _underlyingException.getClass().getName();
		}

	}

	/**
	 * Print the composite message and the embedded stack trace to the specified stream.
	 * @param ps the print stream
	 */
	public void printStackTrace(PrintStream ps) {
		if (_underlyingException == null) {
			super.printStackTrace(ps);
		} else {
			ps.println(this);
			_underlyingException.printStackTrace(ps);
		}
	}

	/**
	 * Print the composite message and the embedded stack trace to the specified writer.
	 * @param pw the print writer
	 */
	public void printStackTrace(PrintWriter pw) {
		if (_underlyingException == null) {
			super.printStackTrace(pw);
		} else {
			pw.println(this);
			_underlyingException.printStackTrace(pw);
		}
	}

}