/*
 * $Header: /home/cvs/jakarta-commons/httpclient/src/java/org/apache/commons/httpclient/HttpException.java,v 1.18 2004/05/13 04:03:24 mbecke Exp $
 * $Revision: 1.18 $
 * $Date: 2004/05/13 04:03:24 $
 *
 * ====================================================================
 *
 *  Copyright 1999-2004 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.commons.httpclient;

import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.lang.reflect.Method;

/**
 * Signals that an HTTP or HttpClient exception has occurred.
 * 
 * @author Laura Werner
 * 
 * @version $Revision: 1.18 $ $Date: 2004/05/13 04:03:24 $
 */
public class HttpException extends IOException {

    /**
     * Creates a new HttpException with a <tt>null</tt> detail message.
     */
    public HttpException() {
        super();
        this.cause = null;
    }

    /**
     * Creates a new HttpException with the specified detail message.
     *
     * @param message the exception detail message
     */
    public HttpException(String message) {
        super(message);
        this.cause = null;
    }

    /**
     * Creates a new HttpException with the specified detail message and cause.
     * 
     * @param message the exception detail message
     * @param cause the <tt>Throwable</tt> that caused this exception, or <tt>null</tt>
     * if the cause is unavailable, unknown, or not a <tt>Throwable</tt>
     * 
     * @since 3.0
     */
    public HttpException(String message, Throwable cause) {
        super(message);
        this.cause = cause;
        
        // If we're running on JDK 1.4 or later, tell Throwable what the cause was
        try {
            Class[] paramsClasses = new Class[] { Throwable.class };
            Method initCause = Throwable.class.getMethod("initCause", paramsClasses);
            initCause.invoke(this, new Object[] { cause });
        } catch (Exception e) {
            // The setCause method must not be available
        }
    }

    /**
     * Return the <tt>Throwable</tt> that caused this exception, or <tt>null</tt>
     *         if the cause is unavailable, unknown, or not a <tt>Throwable</tt>.
     * 
     * @return the <tt>Throwable</tt> that caused this exception, or <tt>null</tt>
     *         if the cause is unavailable, unknown, or not a <tt>Throwable</tt>
     * 
     * @since 3.0
     */
    public Throwable getCause() {
        return cause;
    }

    /**
     * Print this HttpException and its stack trace to the standard error stream.
     * 
     * @since 3.0
     */
    public void printStackTrace() {
        printStackTrace(System.err);
    }

    /**
     * Print this HttpException and its stack trace to the specified print stream.
     * 
     * @param s the <tt>PrintStream</tt> to which the exception and its stack trace
     * should be written
     * 
     * @since 3.0
     */
    public void printStackTrace(PrintStream s) {
        try {
            // JDK 1.4 has a nice printStackTrace method that prints the cause's stack
            // trace too and prunes out duplicate stack frames.  Call it if possible,
            // which is determined by checking whether JDK 1.4's getStackTrace method is present 
            Class[] paramsClasses = new Class[] {  };
            this.getClass().getMethod("getStackTrace", paramsClasses);
            super.printStackTrace(s);
        } catch (Exception ex) {
            // If that didn't work, print it out ourselves
            // First print this exception's stack trace.
            super.printStackTrace(s);
            if (cause != null) {
                // Print out the exception that caused this one.
                // This will recurse if the cause is another HttpException.
                s.print("Caused by: ");
                cause.printStackTrace(s);
            }
        }
    }

    /**
     * Print this HttpException and its stack trace to the specified print writer.
     * 
     * @param s the <tt>PrintWriter</tt> to which the exception and its stack trace
     * should be written
     * 
     * @since 3.0
     */
    public void printStackTrace(PrintWriter s) {
        try {
            // JDK 1.4 has a nice printStackTrace method that prints the cause's stack
            // trace too and prunes out duplicate stack frames.  Call it if possible,
            // which is determined by checking whether JDK 1.4's getStackTrace method is present 
            Class[] paramsClasses = new Class[] {  };
            this.getClass().getMethod("getStackTrace", paramsClasses);
            super.printStackTrace(s);
        } catch (Exception ex) {
            // If that didn't work, print it out ourselves
            // First print this exception's stack trace.
            super.printStackTrace(s);
            if (cause != null) {
                // Print out the exception that caused this one.
                // This will recurse if the cause is another HttpException.
                s.print("Caused by: ");
                cause.printStackTrace(s);
            }
        }
    }

    /** The original Throwable representing the cause of this error */
    private final Throwable cause;
}