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Java > Open Source Codes > org > apache > commons > lang > exception > NestableDelegate


1 /*
2  * Copyright 2002-2005 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.lang.exception;
17
18 import java.io.PrintStream JavaDoc;
19 import java.io.PrintWriter JavaDoc;
20 import java.io.Serializable JavaDoc;
21 import java.io.StringWriter JavaDoc;
22 import java.util.ArrayList JavaDoc;
23 import java.util.Arrays JavaDoc;
24 import java.util.Collections JavaDoc;
25 import java.util.Iterator JavaDoc;
26 import java.util.List JavaDoc;
27
28 /**
29  * <p>A shared implementation of the nestable exception functionality.</p>
30  * <p>
31  * The code is shared between
32  * {@link org.apache.commons.lang.exception.NestableError NestableError},
33  * {@link org.apache.commons.lang.exception.NestableException NestableException} and
34  * {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
35  * </p>
36  *
37  * @author <a HREF="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
38  * @author <a HREF="mailto:dlr@collab.net">Daniel Rall</a>
39  * @author <a HREF="mailto:knielsen@apache.org">Kasper Nielsen</a>
40  * @author <a HREF="mailto:steven@caswell.name">Steven Caswell</a>
41  * @author Sean C. Sullivan
42  * @author Stephen Colebourne
43  * @since 1.0
44  * @version $Id: NestableDelegate.java 161243 2005-04-14 04:30:28Z ggregory $
45  */
46 public class NestableDelegate implements Serializable JavaDoc {
47
48     /**
49      * Constructor error message.
50      */
51     private transient static final String JavaDoc MUST_BE_THROWABLE =
52         "The Nestable implementation passed to the NestableDelegate(Nestable) "
53             + "constructor must extend java.lang.Throwable";
54
55     /**
56      * Holds the reference to the exception or error that we're
57      * wrapping (which must be a {@link
58      * org.apache.commons.lang.exception.Nestable} implementation).
59      */
60     private Throwable JavaDoc nestable = null;
61     
62     /**
63      * Whether to print the stack trace top-down.
64      * This public flag may be set by calling code, typically in initialisation.
65      * This exists for backwards compatability, setting it to false will return
66      * the library to v1.0 behaviour (but will affect all users of the library
67      * in the classloader).
68      * @since 2.0
69      */
70     public static boolean topDown = true;
71     
72     /**
73      * Whether to trim the repeated stack trace.
74      * This public flag may be set by calling code, typically in initialisation.
75      * This exists for backwards compatability, setting it to false will return
76      * the library to v1.0 behaviour (but will affect all users of the library
77      * in the classloader).
78      * @since 2.0
79      */
80     public static boolean trimStackFrames = true;
81     
82     /**
83      * Whether to match subclasses via indexOf.
84      * This public flag may be set by calling code, typically in initialisation.
85      * This exists for backwards compatability, setting it to false will return
86      * the library to v2.0 behaviour (but will affect all users of the library
87      * in the classloader).
88      * @since 2.1
89      */
90     public static boolean matchSubclasses = true;
91
92     /**
93      * Constructs a new <code>NestableDelegate</code> instance to manage the
94      * specified <code>Nestable</code>.
95      *
96      * @param nestable the Nestable implementation (<i>must</i> extend
97      * {@link java.lang.Throwable})
98      * @since 2.0
99      */
100     public NestableDelegate(Nestable nestable) {
101         if (nestable instanceof Throwable JavaDoc) {
102             this.nestable = (Throwable JavaDoc) nestable;
103         } else {
104             throw new IllegalArgumentException JavaDoc(MUST_BE_THROWABLE);
105         }
106     }
107
108     /**
109      * Returns the error message of the <code>Throwable</code> in the chain
110      * of <code>Throwable</code>s at the specified index, numbered from 0.
111      *
112      * @param index the index of the <code>Throwable</code> in the chain of
113      * <code>Throwable</code>s
114      * @return the error message, or null if the <code>Throwable</code> at the
115      * specified index in the chain does not contain a message
116      * @throws IndexOutOfBoundsException if the <code>index</code> argument is
117      * negative or not less than the count of <code>Throwable</code>s in the
118      * chain
119      * @since 2.0
120      */
121     public String JavaDoc getMessage(int index) {
122         Throwable JavaDoc t = this.getThrowable(index);
123         if (Nestable.class.isInstance(t)) {
124             return ((Nestable) t).getMessage(0);
125         } else {
126             return t.getMessage();
127         }
128     }
129
130     /**
131      * Returns the full message contained by the <code>Nestable</code>
132      * and any nested <code>Throwable</code>s.
133      *
134      * @param baseMsg the base message to use when creating the full
135      * message. Should be generally be called via
136      * <code>nestableHelper.getMessage(super.getMessage())</code>,
137      * where <code>super</code> is an instance of {@link
138      * java.lang.Throwable}.
139      * @return The concatenated message for this and all nested
140      * <code>Throwable</code>s
141      * @since 2.0
142      */
143     public String JavaDoc getMessage(String JavaDoc baseMsg) {
144         StringBuffer JavaDoc msg = new StringBuffer JavaDoc();
145         if (baseMsg != null) {
146             msg.append(baseMsg);
147         }
148
149         Throwable JavaDoc nestedCause = ExceptionUtils.getCause(this.nestable);
150         if (nestedCause != null) {
151             String JavaDoc causeMsg = nestedCause.getMessage();
152             if (causeMsg != null) {
153                 if (baseMsg != null) {
154                     msg.append(": ");
155                 }
156                 msg.append(causeMsg);
157             }
158
159         }
160         return msg.length() > 0 ? msg.toString() : null;
161     }
162
163     /**
164      * Returns the error message of this and any nested <code>Throwable</code>s
165      * in an array of Strings, one element for each message. Any
166      * <code>Throwable</code> not containing a message is represented in the
167      * array by a null. This has the effect of cause the length of the returned
168      * array to be equal to the result of the {@link #getThrowableCount()}
169      * operation.
170      *
171      * @return the error messages
172      * @since 2.0
173      */
174     public String JavaDoc[] getMessages() {
175         Throwable JavaDoc[] throwables = this.getThrowables();
176         String JavaDoc[] msgs = new String JavaDoc[throwables.length];
177         for (int i = 0; i < throwables.length; i++) {
178             msgs[i] =
179                 (Nestable.class.isInstance(throwables[i])
180                     ? ((Nestable) throwables[i]).getMessage(0)
181                     : throwables[i].getMessage());
182         }
183         return msgs;
184     }
185
186     /**
187      * Returns the <code>Throwable</code> in the chain of
188      * <code>Throwable</code>s at the specified index, numbered from 0.
189      *
190      * @param index the index, numbered from 0, of the <code>Throwable</code> in
191      * the chain of <code>Throwable</code>s
192      * @return the <code>Throwable</code>
193      * @throws IndexOutOfBoundsException if the <code>index</code> argument is
194      * negative or not less than the count of <code>Throwable</code>s in the
195      * chain
196      * @since 2.0
197      */
198     public Throwable JavaDoc getThrowable(int index) {
199         if (index == 0) {
200             return this.nestable;
201         }
202         Throwable JavaDoc[] throwables = this.getThrowables();
203         return throwables[index];
204     }
205
206     /**
207      * Returns the number of <code>Throwable</code>s contained in the
208      * <code>Nestable</code> contained by this delegate.
209      *
210      * @return the throwable count
211      * @since 2.0
212      */
213     public int getThrowableCount() {
214         return ExceptionUtils.getThrowableCount(this.nestable);
215     }
216
217     /**
218      * Returns this delegate's <code>Nestable</code> and any nested
219      * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
220      * element for each <code>Throwable</code>.
221      *
222      * @return the <code>Throwable</code>s
223      * @since 2.0
224      */
225     public Throwable JavaDoc[] getThrowables() {
226         return ExceptionUtils.getThrowables(this.nestable);
227     }
228
229     /**
230      * Returns the index, numbered from 0, of the first <code>Throwable</code>
231      * that matches the specified type, or a subclass, in the chain of <code>Throwable</code>s
232      * with an index greater than or equal to the specified index.
233      * The method returns -1 if the specified type is not found in the chain.
234      * <p>
235      * NOTE: From v2.1, we have clarified the <code>Nestable</code> interface
236      * such that this method matches subclasses.
237      * If you want to NOT match subclasses, please use
238      * {@link ExceptionUtils#indexOfThrowable(Throwable, Class, int)}
239      * (which is avaiable in all versions of lang).
240      * An alternative is to use the public static flag {@link #matchSubclasses}
241      * on <code>NestableDelegate</code>, however this is not recommended.
242      *
243      * @param type the type to find, subclasses match, null returns -1
244      * @param fromIndex the index, numbered from 0, of the starting position in
245      * the chain to be searched
246      * @return index of the first occurrence of the type in the chain, or -1 if
247      * the type is not found
248      * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
249      * is negative or not less than the count of <code>Throwable</code>s in the
250      * chain
251      * @since 2.0
252      */
253     public int indexOfThrowable(Class JavaDoc type, int fromIndex) {
254         if (type == null) {
255             return -1;
256         }
257         if (fromIndex < 0) {
258             throw new IndexOutOfBoundsException JavaDoc("The start index was out of bounds: " + fromIndex);
259         }
260         Throwable JavaDoc[] throwables = ExceptionUtils.getThrowables(this.nestable);
261         if (fromIndex >= throwables.length) {
262             throw new IndexOutOfBoundsException JavaDoc("The start index was out of bounds: "
263                 + fromIndex + " >= " + throwables.length);
264         }
265         if (matchSubclasses) {
266             for (int i = fromIndex; i < throwables.length; i++) {
267                 if (type.isAssignableFrom(throwables[i].getClass())) {
268                     return i;
269                 }
270             }
271         } else {
272             for (int i = fromIndex; i < throwables.length; i++) {
273                 if (type.equals(throwables[i].getClass())) {
274                     return i;
275                 }
276             }
277         }
278         return -1;
279     }
280
281     /**
282      * Prints the stack trace of this exception the the standar error
283      * stream.
284      */
285     public void printStackTrace() {
286         printStackTrace(System.err);
287     }
288
289     /**
290      * Prints the stack trace of this exception to the specified
291      * stream.
292      *
293      * @param out <code>PrintStream</code> to use for output.
294      * @see #printStackTrace(PrintWriter)
295      */
296     public void printStackTrace(PrintStream JavaDoc out) {
297         synchronized (out) {
298             PrintWriter JavaDoc pw = new PrintWriter JavaDoc(out, false);
299             printStackTrace(pw);
300             // Flush the PrintWriter before it's GC'ed.
301 pw.flush();
302         }
303     }
304
305     /**
306      * Prints the stack trace of this exception to the specified
307      * writer. If the Throwable class has a <code>getCause</code>
308      * method (i.e. running on jre1.4 or higher), this method just
309      * uses Throwable's printStackTrace() method. Otherwise, generates
310      * the stack-trace, by taking into account the 'topDown' and
311      * 'trimStackFrames' parameters. The topDown and trimStackFrames
312      * are set to 'true' by default (produces jre1.4-like stack trace).
313      *
314      * @param out <code>PrintWriter</code> to use for output.
315      */
316     public void printStackTrace(PrintWriter JavaDoc out) {
317         Throwable JavaDoc throwable = this.nestable;
318         // if running on jre1.4 or higher, use default printStackTrace
319 if (ExceptionUtils.isThrowableNested()) {
320             if (throwable instanceof Nestable) {
321                 ((Nestable)throwable).printPartialStackTrace(out);
322             } else {
323                 throwable.printStackTrace(out);
324             }
325             return;
326         }
327
328         // generating the nested stack trace
329 List JavaDoc stacks = new ArrayList JavaDoc();
330         while (throwable != null) {
331             String JavaDoc[] st = getStackFrames(throwable);
332             stacks.add(st);
333             throwable = ExceptionUtils.getCause(throwable);
334         }
335
336         // If NOT topDown, reverse the stack
337 String JavaDoc separatorLine = "Caused by: ";
338         if (!topDown) {
339             separatorLine = "Rethrown as: ";
340             Collections.reverse(stacks);
341         }
342
343         // Remove the repeated lines in the stack
344 if (trimStackFrames) {
345           trimStackFrames(stacks);
346         }
347
348         synchronized (out) {
349             for (Iterator JavaDoc iter=stacks.iterator(); iter.hasNext();) {
350                 String JavaDoc[] st = (String JavaDoc[]) iter.next();
351                 for (int i=0, len=st.length; i < len; i++) {
352                     out.println(st[i]);
353                 }
354                 if (iter.hasNext()) {
355                     out.print(separatorLine);
356                 }
357             }
358         }
359     }
360
361     /**
362      * Captures the stack trace associated with the specified
363      * <code>Throwable</code> object, decomposing it into a list of
364      * stack frames.
365      *
366      * @param t The <code>Throwable</code>.
367      * @return An array of strings describing each stack frame.
368      * @since 2.0
369      */
370     protected String JavaDoc[] getStackFrames(Throwable JavaDoc t) {
371         StringWriter JavaDoc sw = new StringWriter JavaDoc();
372         PrintWriter JavaDoc pw = new PrintWriter JavaDoc(sw, true);
373
374         // Avoid infinite loop between decompose() and printStackTrace().
375 if (t instanceof Nestable) {
376             ((Nestable) t).printPartialStackTrace(pw);
377         } else {
378             t.printStackTrace(pw);
379         }
380         return ExceptionUtils.getStackFrames(sw.getBuffer().toString());
381     }
382     
383     /**
384      * Trims the stack frames. The first set is left untouched. The rest
385      * of the frames are truncated from the bottom by comparing with
386      * one just on top.
387      *
388      * @param stacks The list containing String[] elements
389      * @since 2.0
390      */
391     protected void trimStackFrames(List JavaDoc stacks) {
392          for (int size=stacks.size(), i=size-1; i > 0; i--) {
393              String JavaDoc[] curr = (String JavaDoc[]) stacks.get(i);
394              String JavaDoc[] next = (String JavaDoc[]) stacks.get(i-1);
395              
396              List JavaDoc currList = new ArrayList JavaDoc(Arrays.asList(curr));
397              List JavaDoc nextList = new ArrayList JavaDoc(Arrays.asList(next));
398              ExceptionUtils.removeCommonFrames(currList, nextList);
399
400              int trimmed = curr.length - currList.size();
401              if (trimmed > 0) {
402                  currList.add("\t... "+trimmed+" more");
403                  stacks.set(
404                      i,
405                      currList.toArray(new String JavaDoc[currList.size()])
406                  );
407              }
408          }
409      }
410 }
411
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