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54 package org.jdiagnose.exception;
55
56 import java.io.PrintStream;
57 import java.io.PrintWriter;
58 import java.io.Serializable;
59 import java.io.StringWriter;
60 import java.util.ArrayList;
61 import java.util.Arrays;
62 import java.util.Collections;
63 import java.util.Iterator;
64 import java.util.List;
65
66 /***
67 * <p>A shared implementation of the nestable exception functionality.</p>
68 * <p>
69 * The code is shared between
70 * {@link org.jdiagnose.exception.NestableError NestableError},
71 * {@link org.jdiagnose.exception.NestableException NestableException} and
72 * {@link org.jdiagnose.exception.NestableRuntimeException NestableRuntimeException}.
73 * </p>
74 *
75 * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
76 * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
77 * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
78 * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
79 * @author Sean C. Sullivan
80 * @author Stephen Colebourne
81 * @since 1.0
82 * @version $Id: NestableDelegate.java,v 1.2 2005/03/02 17:07:09 dkfn Exp $
83 */
84 public class NestableDelegate implements Serializable {
85
86 /***
87 * Constructor error message.
88 */
89 private transient static final String MUST_BE_THROWABLE =
90 "The Nestable implementation passed to the NestableDelegate(Nestable) "
91 + "constructor must extend java.lang.Throwable";
92
93 /***
94 * Holds the reference to the exception or error that we're
95 * wrapping (which must be a {@link
96 * org.jdiagnose.exception.Nestable} implementation).
97 */
98 private Throwable nestable = null;
99
100 /***
101 * Whether to print the stack trace top-down.
102 * This public flag may be set by calling code, typically in initialisation.
103 * @since 2.0
104 */
105 public static boolean topDown = true;
106
107 /***
108 * Whether to trim the repeated stack trace.
109 * This public flag may be set by calling code, typically in initialisation.
110 * @since 2.0
111 */
112 public static boolean trimStackFrames = true;
113
114 /***
115 * Constructs a new <code>NestableDelegate</code> instance to manage the
116 * specified <code>Nestable</code>.
117 *
118 * @param nestable the Nestable implementation (<i>must</i> extend
119 * {@link java.lang.Throwable})
120 * @since 2.0
121 */
122 public NestableDelegate(Nestable nestable) {
123 if (nestable instanceof Throwable) {
124 this.nestable = (Throwable) nestable;
125 } else {
126 throw new IllegalArgumentException(MUST_BE_THROWABLE);
127 }
128 }
129
130 /***
131 * Returns the error message of the <code>Throwable</code> in the chain
132 * of <code>Throwable</code>s at the specified index, numbered from 0.
133 *
134 * @param index the index of the <code>Throwable</code> in the chain of
135 * <code>Throwable</code>s
136 * @return the error message, or null if the <code>Throwable</code> at the
137 * specified index in the chain does not contain a message
138 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
139 * negative or not less than the count of <code>Throwable</code>s in the
140 * chain
141 * @since 2.0
142 */
143 public String getMessage(int index) {
144 Throwable t = this.getThrowable(index);
145 if (Nestable.class.isInstance(t)) {
146 return ((Nestable) t).getMessage(0);
147 } else {
148 return t.getMessage();
149 }
150 }
151
152 /***
153 * Returns the full message contained by the <code>Nestable</code>
154 * and any nested <code>Throwable</code>s.
155 *
156 * @param baseMsg the base message to use when creating the full
157 * message. Should be generally be called via
158 * <code>nestableHelper.getMessage(super.getMessage())</code>,
159 * where <code>super</code> is an instance of {@link
160 * java.lang.Throwable}.
161 * @return The concatenated message for this and all nested
162 * <code>Throwable</code>s
163 * @since 2.0
164 */
165 public String getMessage(String baseMsg) {
166 StringBuffer msg = new StringBuffer();
167 if (baseMsg != null) {
168 msg.append(baseMsg);
169 }
170
171 Throwable nestedCause = ExceptionUtils.getCause(this.nestable);
172 if (nestedCause != null) {
173 String causeMsg = nestedCause.getMessage();
174 if (causeMsg != null) {
175 if (baseMsg != null) {
176 msg.append(": ");
177 }
178 msg.append(causeMsg);
179 }
180
181 }
182 return (msg.length() > 0 ? msg.toString() : null);
183 }
184
185 /***
186 * Returns the error message of this and any nested <code>Throwable</code>s
187 * in an array of Strings, one element for each message. Any
188 * <code>Throwable</code> not containing a message is represented in the
189 * array by a null. This has the effect of cause the length of the returned
190 * array to be equal to the result of the {@link #getThrowableCount()}
191 * operation.
192 *
193 * @return the error messages
194 * @since 2.0
195 */
196 public String[] getMessages() {
197 Throwable[] throwables = this.getThrowables();
198 String[] msgs = new String[throwables.length];
199 for (int i = 0; i < throwables.length; i++) {
200 msgs[i] =
201 (Nestable.class.isInstance(throwables[i])
202 ? ((Nestable) throwables[i]).getMessage(0)
203 : throwables[i].getMessage());
204 }
205 return msgs;
206 }
207
208 /***
209 * Returns the <code>Throwable</code> in the chain of
210 * <code>Throwable</code>s at the specified index, numbered from 0.
211 *
212 * @param index the index, numbered from 0, of the <code>Throwable</code> in
213 * the chain of <code>Throwable</code>s
214 * @return the <code>Throwable</code>
215 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
216 * negative or not less than the count of <code>Throwable</code>s in the
217 * chain
218 * @since 2.0
219 */
220 public Throwable getThrowable(int index) {
221 if (index == 0) {
222 return this.nestable;
223 }
224 Throwable[] throwables = this.getThrowables();
225 return throwables[index];
226 }
227
228 /***
229 * Returns the number of <code>Throwable</code>s contained in the
230 * <code>Nestable</code> contained by this remoteResult.
231 *
232 * @return the throwable count
233 * @since 2.0
234 */
235 public int getThrowableCount() {
236 return ExceptionUtils.getThrowableCount(this.nestable);
237 }
238
239 /***
240 * Returns this remoteResult's <code>Nestable</code> and any nested
241 * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
242 * element for each <code>Throwable</code>.
243 *
244 * @return the <code>Throwable</code>s
245 * @since 2.0
246 */
247 public Throwable[] getThrowables() {
248 return ExceptionUtils.getThrowables(this.nestable);
249 }
250
251 /***
252 * Returns the index, numbered from 0, of the first <code>Throwable</code>
253 * that matches the specified type in the chain of <code>Throwable</code>s
254 * held in this remoteResult's <code>Nestable</code> with an index greater than
255 * or equal to the specified index, or -1 if the type is not found.
256 *
257 * @param type <code>Class</code> to be found
258 * @param fromIndex the index, numbered from 0, of the starting position in
259 * the chain to be searched
260 * @return index of the first occurrence of the type in the chain, or -1 if
261 * the type is not found
262 * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
263 * is negative or not less than the count of <code>Throwable</code>s in the
264 * chain
265 * @since 2.0
266 */
267 public int indexOfThrowable(Class type, int fromIndex) {
268 if (fromIndex < 0) {
269 throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
270 }
271 Throwable[] throwables = ExceptionUtils.getThrowables(this.nestable);
272 if (fromIndex >= throwables.length) {
273 throw new IndexOutOfBoundsException("The start index was out of bounds: "
274 + fromIndex + " >= " + throwables.length);
275 }
276 for (int i = fromIndex; i < throwables.length; i++) {
277 if (throwables[i].getClass().equals(type)) {
278 return i;
279 }
280 }
281 return -1;
282 }
283
284 /***
285 * Prints the stack trace of this exception the the standar error
286 * stream.
287 */
288 public void printStackTrace() {
289 printStackTrace(System.err);
290 }
291
292 /***
293 * Prints the stack trace of this exception to the specified
294 * stream.
295 *
296 * @param out <code>PrintStream</code> to use for output.
297 * @see #printStackTrace(PrintWriter)
298 */
299 public void printStackTrace(PrintStream out) {
300 synchronized (out) {
301 PrintWriter pw = new PrintWriter(out, false);
302 printStackTrace(pw);
303
304 pw.flush();
305 }
306 }
307
308 /***
309 * Prints the stack trace of this exception to the specified
310 * writer. If the Throwable class has a <code>getCause</code>
311 * method (i.e. running on jre1.4 or higher), this method just
312 * uses Throwable's printStackTrace() method. Otherwise, generates
313 * the stack-trace, by taking into account the 'topDown' and
314 * 'trimStackFrames' parameters. The topDown and trimStackFrames
315 * are set to 'true' by default (produces jre1.4-like stack trace).
316 *
317 * @param out <code>PrintWriter</code> to use for output.
318 */
319 public void printStackTrace(PrintWriter out) {
320 Throwable throwable = this.nestable;
321
322 if (ExceptionUtils.isThrowableNested()) {
323 if (throwable instanceof Nestable) {
324 ((Nestable)throwable).printPartialStackTrace(out);
325 } else {
326 throwable.printStackTrace(out);
327 }
328 return;
329 }
330
331
332 List stacks = new ArrayList();
333 while (throwable != null) {
334 String[] st = getStackFrames(throwable);
335 stacks.add(st);
336 throwable = ExceptionUtils.getCause(throwable);
337 }
338
339
340 String separatorLine = "Caused by: ";
341 if (!topDown) {
342 separatorLine = "Rethrown as: ";
343 Collections.reverse(stacks);
344 }
345
346
347 if (trimStackFrames) {
348 trimStackFrames(stacks);
349 }
350
351 synchronized (out) {
352 for (Iterator iter=stacks.iterator(); iter.hasNext();) {
353 String[] st = (String[]) iter.next();
354 for (int i=0, len=st.length; i < len; i++) {
355 out.println(st[i]);
356 }
357 if (iter.hasNext()) {
358 out.print(separatorLine);
359 }
360 }
361 }
362 }
363
364 /***
365 * Captures the stack trace associated with the specified
366 * <code>Throwable</code> object, decomposing it into a list of
367 * stack frames.
368 *
369 * @param t The <code>Throwable</code>.
370 * @return An array of strings describing each stack frame.
371 * @since 2.0
372 */
373 protected String[] getStackFrames(Throwable t) {
374 StringWriter sw = new StringWriter();
375 PrintWriter pw = new PrintWriter(sw, true);
376
377
378 if (t instanceof Nestable) {
379 ((Nestable) t).printPartialStackTrace(pw);
380 } else {
381 t.printStackTrace(pw);
382 }
383 return ExceptionUtils.getStackFrames(sw.getBuffer().toString());
384 }
385
386 /***
387 * Trims the stack frames. The first set is left untouched. The rest
388 * of the frames are truncated from the bottom by comparing with
389 * one just on top.
390 *
391 * @param stacks The list containing String[] elements
392 * @since 2.0
393 */
394 protected void trimStackFrames(List stacks) {
395 for (int size=stacks.size(), i=size-1; i > 0; i--) {
396 String[] curr = (String[]) stacks.get(i);
397 String[] next = (String[]) stacks.get(i-1);
398
399 List currList = new ArrayList(Arrays.asList(curr));
400 List nextList = new ArrayList(Arrays.asList(next));
401 ExceptionUtils.removeCommonFrames(currList, nextList);
402
403 int trimmed = curr.length - currList.size();
404 if (trimmed > 0) {
405 currList.add("\t... "+trimmed+" more");
406 stacks.set(
407 i,
408 currList.toArray(new String[currList.size()])
409 );
410 }
411 }
412 }
413 }