ExceptionUnwrapper


1   /*-
2    * See the file LICENSE for redistribution information.
3    *
4    * Copyright (c) 2000,2006 Oracle.  All rights reserved.
5    *
6    * $Id: ExceptionUnwrapper.java,v 1.16 2006/10/30 21:14:34 bostic Exp $
7    */
8   
9   package com.sleepycat.util;
10  
11  /**
12   * Unwraps nested exceptions by calling the {@link
13   * ExceptionWrapper#getCause()} method for exceptions that implement the
14   * {@link ExceptionWrapper} interface.  Does not currently support the Java 1.4
15   * <code>Throwable.getCause()</code> method.
16   *
17   * @author Mark Hayes
18   */
19  public class ExceptionUnwrapper {
20  
21      /**
22       * Unwraps an Exception and returns the underlying Exception, or throws an
23       * Error if the underlying Throwable is an Error.
24       *
25       * @param e is the Exception to unwrap.
26       *
27       * @return the underlying Exception.
28       *
29       * @throws Error if the underlying Throwable is an Error.
30       *
31       * @throws IllegalArgumentException if the underlying Throwable is not an
32       * Exception or an Error.
33       */
34      public static Exception   unwrap(Exception   e) {
35  
36          Throwable   t = unwrapAny(e);
37          if (t instanceof Exception  ) {
38              return (Exception  ) t;
39          } else if (t instanceof Error  ) {
40              throw (Error  ) t;
41          } else {
42              throw new IllegalArgumentException  ("Not Exception or Error: " + t);
43          }
44      }
45  
46      /**
47       * Unwraps an Exception and returns the underlying Throwable.
48       *
49       * @param e is the Exception to unwrap.
50       *
51       * @return the underlying Throwable.
52       */
53      public static Throwable   unwrapAny(Throwable   e) {
54  
55          while (true) {
56              if (e instanceof ExceptionWrapper) {
57                  Throwable   e2 = ((ExceptionWrapper) e).getCause();
58                  if (e2 == null) {
59                      return e;
60                  } else {
61                      e = e2;
62                  }
63              } else {
64                  return e;
65              }
66          }
67      }
68  }
69
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