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Java > Open Source Codes > org > apache > commons > httpclient > util > ExceptionUtil


1 /*
2  * $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 $
3  * $Revision: 480424 $
4  * $Date: 2006-11-29 05:56:49 +0000 (Wed, 29 Nov 2006) $
5  *
6  * ====================================================================
7  *
8  * Licensed to the Apache Software Foundation (ASF) under one or more
9  * contributor license agreements. See the NOTICE file distributed with
10  * this work for additional information regarding copyright ownership.
11  * The ASF licenses this file to You under the Apache License, Version 2.0
12  * (the "License"); you may not use this file except in compliance with
13  * the License. You may obtain a copy of the License at
14  *
15  * http://www.apache.org/licenses/LICENSE-2.0
16  *
17  * Unless required by applicable law or agreed to in writing, software
18  * distributed under the License is distributed on an "AS IS" BASIS,
19  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
20  * See the License for the specific language governing permissions and
21  * limitations under the License.
22  * ====================================================================
23  *
24  * This software consists of voluntary contributions made by many
25  * individuals on behalf of the Apache Software Foundation. For more
26  * information on the Apache Software Foundation, please see
27  * <http://www.apache.org/>.
28  *
29  */
30 package org.apache.commons.httpclient.util;
31
32 import java.io.InterruptedIOException JavaDoc;
33 import java.lang.reflect.Method JavaDoc;
34
35 import org.apache.commons.logging.Log;
36 import org.apache.commons.logging.LogFactory;
37
38 /**
39  * The home for utility methods that handle various exception-related tasks.
40  *
41  * @author <a HREF="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
42  * @author <a HREF="mailto:laura@lwerner.org">Laura Werner</a>
43  *
44  * @since 3.0
45  */
46 public class ExceptionUtil {
47
48     /** Log object for this class. */
49     private static final Log LOG = LogFactory.getLog(ExceptionUtil.class);
50
51     /** A reference to Throwable's initCause method, or null if it's not there in this JVM */
52     static private final Method JavaDoc INIT_CAUSE_METHOD = getInitCauseMethod();
53
54     /** A reference to SocketTimeoutExceptionClass class, or null if it's not there in this JVM */
55     static private final Class JavaDoc SOCKET_TIMEOUT_CLASS = SocketTimeoutExceptionClass();
56     
57     /**
58      * Returns a <code>Method<code> allowing access to
59      * {@link Throwable.initCause(Throwable) initCause} method of {@link Throwable},
60      * or <code>null</code> if the method
61      * does not exist.
62      *
63      * @return A <code>Method<code> for <code>Throwable.initCause</code>, or
64      * <code>null</code> if unavailable.
65      */
66     static private Method JavaDoc getInitCauseMethod() {
67         try {
68             Class JavaDoc[] paramsClasses = new Class JavaDoc[] { Throwable JavaDoc.class };
69             return Throwable JavaDoc.class.getMethod("initCause", paramsClasses);
70         } catch (NoSuchMethodException JavaDoc e) {
71             return null;
72         }
73     }
74     
75     /**
76      * Returns <code>SocketTimeoutExceptionClass<code> or <code>null</code> if the class
77      * does not exist.
78      *
79      * @return <code>SocketTimeoutExceptionClass<code>, or <code>null</code> if unavailable.
80      */
81     static private Class JavaDoc SocketTimeoutExceptionClass() {
82         try {
83             return Class.forName("java.net.SocketTimeoutException");
84         } catch (ClassNotFoundException JavaDoc e) {
85             return null;
86         }
87     }
88     
89     /**
90      * If we're running on JDK 1.4 or later, initialize the cause for the given throwable.
91      *
92      * @param throwable The throwable.
93      * @param cause The cause of the throwable.
94      */
95     public static void initCause(Throwable JavaDoc throwable, Throwable JavaDoc cause) {
96         if (INIT_CAUSE_METHOD != null) {
97             try {
98                 INIT_CAUSE_METHOD.invoke(throwable, new Object JavaDoc[] { cause });
99             } catch (Exception JavaDoc e) {
100                 LOG.warn("Exception invoking Throwable.initCause", e);
101             }
102         }
103     }
104
105     /**
106      * If SocketTimeoutExceptionClass is defined, returns <tt>true</tt> only if the
107      * exception is an instance of SocketTimeoutExceptionClass. If
108      * SocketTimeoutExceptionClass is undefined, always returns <tt>true</tt>.
109      *
110      * @param e an instance of InterruptedIOException class.
111      *
112      * @return <tt>true</tt> if the exception signals socket timeout, <tt>false</tt>
113      * otherwise.
114      */
115     public static boolean isSocketTimeoutException(final InterruptedIOException JavaDoc e) {
116         if (SOCKET_TIMEOUT_CLASS != null) {
117             return SOCKET_TIMEOUT_CLASS.isInstance(e);
118         } else {
119             return true;
120         }
121     }
122 }
123
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