/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/util/ExceptionUtil.java,v 1.5 2004/10/19 18:09:46 olegk Exp $
* $Revision: 480424 $
* $Date: 2006-11-29 06:56:49 +0100 (Wed, 29 Nov 2006) $
*
* ====================================================================
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.util;
import java.io.InterruptedIOException;
import java.lang.reflect.Method;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* The home for utility methods that handle various exception-related tasks.
*
* @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
* @author <a href="mailto:laura@lwerner.org">Laura Werner</a>
*
* @since 3.0
*/
public class ExceptionUtil {
/** Log object for this class. */
private static final Log LOG = LogFactory.getLog(ExceptionUtil.class);
/** A reference to Throwable's initCause method, or null if it's not there in this JVM */
static private final Method INIT_CAUSE_METHOD = getInitCauseMethod();
/** A reference to SocketTimeoutExceptionClass class, or null if it's not there in this JVM */
static private final Class SOCKET_TIMEOUT_CLASS = SocketTimeoutExceptionClass();
/**
* Returns a <code>Method<code> allowing access to
* {@link Throwable.initCause(Throwable) initCause} method of {@link Throwable},
* or <code>null</code> if the method
* does not exist.
*
* @return A <code>Method<code> for <code>Throwable.initCause</code>, or
* <code>null</code> if unavailable.
*/
static private Method getInitCauseMethod() {
try {
Class[] paramsClasses = new Class[] { Throwable.class };
return Throwable.class.getMethod("initCause", paramsClasses);
} catch (NoSuchMethodException e) {
return null;
}
}
/**
* Returns <code>SocketTimeoutExceptionClass<code> or <code>null</code> if the class
* does not exist.
*
* @return <code>SocketTimeoutExceptionClass<code>, or <code>null</code> if unavailable.
*/
static private Class SocketTimeoutExceptionClass() {
try {
return Class.forName("java.net.SocketTimeoutException");
} catch (ClassNotFoundException e) {
return null;
}
}
/**
* If we're running on JDK 1.4 or later, initialize the cause for the given throwable.
*
* @param throwable The throwable.
* @param cause The cause of the throwable.
*/
public static void initCause(Throwable throwable, Throwable cause) {
if (INIT_CAUSE_METHOD != null) {
try {
INIT_CAUSE_METHOD.invoke(throwable, new Object[] { cause });
} catch (Exception e) {
LOG.warn("Exception invoking Throwable.initCause", e);
}
}
}
/**
* If SocketTimeoutExceptionClass is defined, returns <tt>true</tt> only if the
* exception is an instance of SocketTimeoutExceptionClass. If
* SocketTimeoutExceptionClass is undefined, always returns <tt>true</tt>.
*
* @param e an instance of InterruptedIOException class.
*
* @return <tt>true</tt> if the exception signals socket timeout, <tt>false</tt>
* otherwise.
*/
public static boolean isSocketTimeoutException(final InterruptedIOException e) {
if (SOCKET_TIMEOUT_CLASS != null) {
return SOCKET_TIMEOUT_CLASS.isInstance(e);
} else {
return true;
}
}
}