001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.lang.exception;
018
019 import java.io.PrintStream;
020 import java.io.PrintWriter;
021 import java.io.Serializable;
022 import java.io.StringWriter;
023 import java.util.ArrayList;
024 import java.util.Arrays;
025 import java.util.Collections;
026 import java.util.Iterator;
027 import java.util.List;
028
029 /**
030 * <p>A shared implementation of the nestable exception functionality.</p>
031 * <p>
032 * The code is shared between
033 * {@link org.apache.commons.lang.exception.NestableError NestableError},
034 * {@link org.apache.commons.lang.exception.NestableException NestableException} and
035 * {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
036 * </p>
037 *
038 * @author Apache Software Foundation
039 * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
040 * @author Daniel L. Rall
041 * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
042 * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
043 * @author Sean C. Sullivan
044 * @since 1.0
045 * @version $Id: NestableDelegate.java 905636 2010-02-02 14:03:32Z niallp $
046 */
047 public class NestableDelegate implements Serializable {
048
049 /**
050 * Required for serialization support.
051 *
052 * @see java.io.Serializable
053 */
054 private static final long serialVersionUID = 1L;
055
056 /**
057 * Constructor error message.
058 */
059 private transient static final String MUST_BE_THROWABLE =
060 "The Nestable implementation passed to the NestableDelegate(Nestable) "
061 + "constructor must extend java.lang.Throwable";
062
063 /**
064 * Holds the reference to the exception or error that we're
065 * wrapping (which must be a {@link
066 * org.apache.commons.lang.exception.Nestable} implementation).
067 */
068 private Throwable nestable = null;
069
070 /**
071 * Whether to print the stack trace top-down.
072 * This public flag may be set by calling code, typically in initialisation.
073 * This exists for backwards compatability, setting it to false will return
074 * the library to v1.0 behaviour (but will affect all users of the library
075 * in the classloader).
076 * @since 2.0
077 */
078 public static boolean topDown = true;
079
080 /**
081 * Whether to trim the repeated stack trace.
082 * This public flag may be set by calling code, typically in initialisation.
083 * This exists for backwards compatability, setting it to false will return
084 * the library to v1.0 behaviour (but will affect all users of the library
085 * in the classloader).
086 * @since 2.0
087 */
088 public static boolean trimStackFrames = true;
089
090 /**
091 * Whether to match subclasses via indexOf.
092 * This public flag may be set by calling code, typically in initialisation.
093 * This exists for backwards compatability, setting it to false will return
094 * the library to v2.0 behaviour (but will affect all users of the library
095 * in the classloader).
096 * @since 2.1
097 */
098 public static boolean matchSubclasses = true;
099
100 /**
101 * Constructs a new <code>NestableDelegate</code> instance to manage the
102 * specified <code>Nestable</code>.
103 *
104 * @param nestable the Nestable implementation (<i>must</i> extend
105 * {@link java.lang.Throwable})
106 * @since 2.0
107 */
108 public NestableDelegate(Nestable nestable) {
109 if (nestable instanceof Throwable) {
110 this.nestable = (Throwable) nestable;
111 } else {
112 throw new IllegalArgumentException(MUST_BE_THROWABLE);
113 }
114 }
115
116 /**
117 * Returns the error message of the <code>Throwable</code> in the chain of <code>Throwable</code>s at the
118 * specified index, numbered from 0.
119 *
120 * @param index
121 * the index of the <code>Throwable</code> in the chain of <code>Throwable</code>s
122 * @return the error message, or null if the <code>Throwable</code> at the specified index in the chain does not
123 * contain a message
124 * @throws IndexOutOfBoundsException
125 * if the <code>index</code> argument is negative or not less than the count of <code>Throwable</code>s
126 * in the chain
127 * @since 2.0
128 */
129 public String getMessage(int index) {
130 Throwable t = this.getThrowable(index);
131 if (Nestable.class.isInstance(t)) {
132 return ((Nestable) t).getMessage(0);
133 }
134 return t.getMessage();
135 }
136
137 /**
138 * Returns the full message contained by the <code>Nestable</code> and any nested <code>Throwable</code>s.
139 *
140 * @param baseMsg
141 * the base message to use when creating the full message. Should be generally be called via
142 * <code>nestableHelper.getMessage(super.getMessage())</code>, where <code>super</code> is an
143 * instance of {@link java.lang.Throwable}.
144 * @return The concatenated message for this and all nested <code>Throwable</code>s
145 * @since 2.0
146 */
147 public String getMessage(String baseMsg) {
148 Throwable nestedCause = ExceptionUtils.getCause(this.nestable);
149 String causeMsg = nestedCause == null ? null : nestedCause.getMessage();
150 if (nestedCause == null || causeMsg == null) {
151 return baseMsg; // may be null, which is a valid result
152 }
153 if (baseMsg == null) {
154 return causeMsg;
155 }
156 return baseMsg + ": " + causeMsg;
157 }
158
159 /**
160 * Returns the error message of this and any nested <code>Throwable</code>s in an array of Strings, one element
161 * for each message. Any <code>Throwable</code> not containing a message is represented in the array by a null.
162 * This has the effect of cause the length of the returned array to be equal to the result of the
163 * {@link #getThrowableCount()} operation.
164 *
165 * @return the error messages
166 * @since 2.0
167 */
168 public String[] getMessages() {
169 Throwable[] throwables = this.getThrowables();
170 String[] msgs = new String[throwables.length];
171 for (int i = 0; i < throwables.length; i++) {
172 msgs[i] =
173 (Nestable.class.isInstance(throwables[i])
174 ? ((Nestable) throwables[i]).getMessage(0)
175 : throwables[i].getMessage());
176 }
177 return msgs;
178 }
179
180 /**
181 * Returns the <code>Throwable</code> in the chain of
182 * <code>Throwable</code>s at the specified index, numbered from 0.
183 *
184 * @param index the index, numbered from 0, of the <code>Throwable</code> in
185 * the chain of <code>Throwable</code>s
186 * @return the <code>Throwable</code>
187 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
188 * negative or not less than the count of <code>Throwable</code>s in the
189 * chain
190 * @since 2.0
191 */
192 public Throwable getThrowable(int index) {
193 if (index == 0) {
194 return this.nestable;
195 }
196 Throwable[] throwables = this.getThrowables();
197 return throwables[index];
198 }
199
200 /**
201 * Returns the number of <code>Throwable</code>s contained in the
202 * <code>Nestable</code> contained by this delegate.
203 *
204 * @return the throwable count
205 * @since 2.0
206 */
207 public int getThrowableCount() {
208 return ExceptionUtils.getThrowableCount(this.nestable);
209 }
210
211 /**
212 * Returns this delegate's <code>Nestable</code> and any nested
213 * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
214 * element for each <code>Throwable</code>.
215 *
216 * @return the <code>Throwable</code>s
217 * @since 2.0
218 */
219 public Throwable[] getThrowables() {
220 return ExceptionUtils.getThrowables(this.nestable);
221 }
222
223 /**
224 * Returns the index, numbered from 0, of the first <code>Throwable</code>
225 * that matches the specified type, or a subclass, in the chain of <code>Throwable</code>s
226 * with an index greater than or equal to the specified index.
227 * The method returns -1 if the specified type is not found in the chain.
228 * <p>
229 * NOTE: From v2.1, we have clarified the <code>Nestable</code> interface
230 * such that this method matches subclasses.
231 * If you want to NOT match subclasses, please use
232 * {@link ExceptionUtils#indexOfThrowable(Throwable, Class, int)}
233 * (which is avaiable in all versions of lang).
234 * An alternative is to use the public static flag {@link #matchSubclasses}
235 * on <code>NestableDelegate</code>, however this is not recommended.
236 *
237 * @param type the type to find, subclasses match, null returns -1
238 * @param fromIndex the index, numbered from 0, of the starting position in
239 * the chain to be searched
240 * @return index of the first occurrence of the type in the chain, or -1 if
241 * the type is not found
242 * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
243 * is negative or not less than the count of <code>Throwable</code>s in the
244 * chain
245 * @since 2.0
246 */
247 public int indexOfThrowable(Class type, int fromIndex) {
248 if (type == null) {
249 return -1;
250 }
251 if (fromIndex < 0) {
252 throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
253 }
254 Throwable[] throwables = ExceptionUtils.getThrowables(this.nestable);
255 if (fromIndex >= throwables.length) {
256 throw new IndexOutOfBoundsException("The start index was out of bounds: "
257 + fromIndex + " >= " + throwables.length);
258 }
259 if (matchSubclasses) {
260 for (int i = fromIndex; i < throwables.length; i++) {
261 if (type.isAssignableFrom(throwables[i].getClass())) {
262 return i;
263 }
264 }
265 } else {
266 for (int i = fromIndex; i < throwables.length; i++) {
267 if (type.equals(throwables[i].getClass())) {
268 return i;
269 }
270 }
271 }
272 return -1;
273 }
274
275 /**
276 * Prints the stack trace of this exception the the standar error
277 * stream.
278 */
279 public void printStackTrace() {
280 printStackTrace(System.err);
281 }
282
283 /**
284 * Prints the stack trace of this exception to the specified
285 * stream.
286 *
287 * @param out <code>PrintStream</code> to use for output.
288 * @see #printStackTrace(PrintWriter)
289 */
290 public void printStackTrace(PrintStream out) {
291 synchronized (out) {
292 PrintWriter pw = new PrintWriter(out, false);
293 printStackTrace(pw);
294 // Flush the PrintWriter before it's GC'ed.
295 pw.flush();
296 }
297 }
298
299 /**
300 * Prints the stack trace of this exception to the specified
301 * writer. If the Throwable class has a <code>getCause</code>
302 * method (i.e. running on jre1.4 or higher), this method just
303 * uses Throwable's printStackTrace() method. Otherwise, generates
304 * the stack-trace, by taking into account the 'topDown' and
305 * 'trimStackFrames' parameters. The topDown and trimStackFrames
306 * are set to 'true' by default (produces jre1.4-like stack trace).
307 *
308 * @param out <code>PrintWriter</code> to use for output.
309 */
310 public void printStackTrace(PrintWriter out) {
311 Throwable throwable = this.nestable;
312 // if running on jre1.4 or higher, use default printStackTrace
313 if (ExceptionUtils.isThrowableNested()) {
314 if (throwable instanceof Nestable) {
315 ((Nestable)throwable).printPartialStackTrace(out);
316 } else {
317 throwable.printStackTrace(out);
318 }
319 return;
320 }
321
322 // generating the nested stack trace
323 List stacks = new ArrayList();
324 while (throwable != null) {
325 String[] st = getStackFrames(throwable);
326 stacks.add(st);
327 throwable = ExceptionUtils.getCause(throwable);
328 }
329
330 // If NOT topDown, reverse the stack
331 String separatorLine = "Caused by: ";
332 if (!topDown) {
333 separatorLine = "Rethrown as: ";
334 Collections.reverse(stacks);
335 }
336
337 // Remove the repeated lines in the stack
338 if (trimStackFrames) {
339 trimStackFrames(stacks);
340 }
341
342 synchronized (out) {
343 for (Iterator iter=stacks.iterator(); iter.hasNext();) {
344 String[] st = (String[]) iter.next();
345 for (int i=0, len=st.length; i < len; i++) {
346 out.println(st[i]);
347 }
348 if (iter.hasNext()) {
349 out.print(separatorLine);
350 }
351 }
352 }
353 }
354
355 /**
356 * Captures the stack trace associated with the specified
357 * <code>Throwable</code> object, decomposing it into a list of
358 * stack frames.
359 *
360 * @param t The <code>Throwable</code>.
361 * @return An array of strings describing each stack frame.
362 * @since 2.0
363 */
364 protected String[] getStackFrames(Throwable t) {
365 StringWriter sw = new StringWriter();
366 PrintWriter pw = new PrintWriter(sw, true);
367
368 // Avoid infinite loop between decompose() and printStackTrace().
369 if (t instanceof Nestable) {
370 ((Nestable) t).printPartialStackTrace(pw);
371 } else {
372 t.printStackTrace(pw);
373 }
374 return ExceptionUtils.getStackFrames(sw.getBuffer().toString());
375 }
376
377 /**
378 * Trims the stack frames. The first set is left untouched. The rest
379 * of the frames are truncated from the bottom by comparing with
380 * one just on top.
381 *
382 * @param stacks The list containing String[] elements
383 * @since 2.0
384 */
385 protected void trimStackFrames(List stacks) {
386 for (int size=stacks.size(), i=size-1; i > 0; i--) {
387 String[] curr = (String[]) stacks.get(i);
388 String[] next = (String[]) stacks.get(i-1);
389
390 List currList = new ArrayList(Arrays.asList(curr));
391 List nextList = new ArrayList(Arrays.asList(next));
392 ExceptionUtils.removeCommonFrames(currList, nextList);
393
394 int trimmed = curr.length - currList.size();
395 if (trimmed > 0) {
396 currList.add("\t... "+trimmed+" more");
397 stacks.set(
398 i,
399 currList.toArray(new String[currList.size()])
400 );
401 }
402 }
403 }
404 }