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1 /* ====================================================================
2 * License:
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in
13 * the documentation and/or other materials provided with the
14 * distribution.
15 *
16 * 3. The end-user documentation included with the redistribution,
17 * if any, must include the following acknowledgment:
18 * "This product includes software developed by
19 * Robert Half International (http://www.rhi.com/)."
20 * Alternately, this acknowledgment may appear in the software itself,
21 * if and wherever such third-party acknowledgments normally appear.
22 *
23 * 4. The names "Parc", "RHI", and "Robert Half International" must
24 * not be used to endorse or promote products derived from this
25 * software without prior written permission. For written
26 * permission, please contact pete.mckinstry@rhi.com.
27 *
28 * 5. Products derived from this software may not be called "PARC",
29 * nor may "PARC" appear in their name, without prior written
30 * permission of Robert Half International.
31 *
32 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
33 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
34 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
35 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
36 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
37 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
38 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
39 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
40 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
41 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
42 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
43 * SUCH DAMAGE.
44 * ====================================================================
45 *
46 */
47 package com.rhi.architecture.parc;
48
49 import java.util.ArrayList;
50 import java.util.List;
51
52 /***
53 * The handler class is designed for critical failures during
54 * filter processing. Since Filters are executed w/in one or
55 * more threads, they cannot propagate errors up the call
56 * stack to the main thread. To remedy this problem, the
57 * ExceptionHandler is made available to Filters to report
58 * critical FATAL processing errors. It is shared by all the
59 * threads (including the main thread running the pipeline)
60 * and is checked @ the end of each cycle so that application
61 * shutdown can happen cleanly as soon as possible.
62 * This is a common pattern for error reporting in a multi-
63 * threaded environment.
64 *
65 * @author Pete McKinstry
66 * @copyright 2002, Robert Half Int'l., Inc. All rights reserved.
67 *
68 * @since 1.0
69 */
70 public class ExceptionHandler {
71
72 /***
73 * list of reported exceptions. Normally the pipeline will
74 * shutdown as soon as a fatal error occurs, but the timing
75 * may allow for multiple exceptions to be reported before
76 * the pipeline is notified and/or can react. Therefore a list
77 * is maintained to store any subsequent errors reporting
78 * during the interim.
79 */
80 private List exceptions = new ArrayList();
81
82 // lock for thread safety.
83 private Object lock = new Object();
84
85 private boolean hasError = false;
86
87 /***
88 * Default constructor
89 *
90 * @since 1.0
91 */
92 public ExceptionHandler() {
93 super();
94 }
95
96 /***
97 * Method used by Filters to report a fatal error.
98 *
99 * @param e
100 * @since 1.0
101 */
102 public void reportException(ProcessingException e) {
103 synchronized (lock) {
104 exceptions.add(e);
105 hasError = true;
106 }
107 }
108
109 /***
110 * Rethrow the first reported exception.
111 *
112 * @throws ProcessingException
113 * @since 1.0
114 */
115 public void rethrowException() throws ProcessingException {
116
117 synchronized (lock) {
118 // locks are re-entrant, it's ok that hasError is
119 // synchronized on 'lock' also.
120 if (hasError()) {
121 // get first exception
122 throw (ProcessingException) exceptions.get(0);
123 }
124 }
125 }
126
127 /***
128 * True/False flag allowing the pipeline components to recognize
129 * when a fatal error has been reported.
130 * @return boolean
131 *
132 * @since 1.0
133 */
134 public boolean hasError() {
135 synchronized (lock) {
136 return this.hasError;
137 }
138 }
139
140 }
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