1 /*
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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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8  * particular file as subject to the "Classpath" exception as provided
9  * by Oracle in the LICENSE file that accompanied this code.
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11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
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19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24  */
25 
26 package java.lang;
27 
28 import java.io.IOException;
29 import java.io.ObjectInputStream;
30 import java.io.ObjectOutputStream;
31 import java.io.ObjectStreamField;
32 
33 /**
34  * Thrown when an application tries to load in a class through its
35  * string name using:
36  * <ul>
37  * <li>The <code>forName</code> method in class <code>Class</code>.
38  * <li>The <code>findSystemClass</code> method in class
39  *     <code>ClassLoader</code> .
40  * <li>The <code>loadClass</code> method in class <code>ClassLoader</code>.
41  * </ul>
42  * <p>
43  * but no definition for the class with the specified name could be found.
44  *
45  * <p>As of release 1.4, this exception has been retrofitted to conform to
46  * the general purpose exception-chaining mechanism.  The "optional exception
47  * that was raised while loading the class" that may be provided at
48  * construction time and accessed via the {@link #getException()} method is
49  * now known as the <i>cause</i>, and may be accessed via the {@link
50  * Throwable#getCause()} method, as well as the aforementioned "legacy method."
51  *
52  * @author  unascribed
53  * @see     java.lang.Class#forName(java.lang.String)
54  * @see     java.lang.ClassLoader#findSystemClass(java.lang.String)
55  * @see     java.lang.ClassLoader#loadClass(java.lang.String, boolean)
56  * @since   1.0
57  */
58 public class ClassNotFoundException extends ReflectiveOperationException {
59     /**
60      * use serialVersionUID from JDK 1.1.X for interoperability
61      */
62      private static final long serialVersionUID = 9176873029745254542L;
63 
64     /**
65      * Constructs a <code>ClassNotFoundException</code> with no detail message.
66      */
ClassNotFoundException()67     public ClassNotFoundException() {
68         super((Throwable)null);  // Disallow initCause
69     }
70 
71     /**
72      * Constructs a <code>ClassNotFoundException</code> with the
73      * specified detail message.
74      *
75      * @param   s   the detail message.
76      */
ClassNotFoundException(String s)77     public ClassNotFoundException(String s) {
78         super(s, null);  //  Disallow initCause
79     }
80 
81     /**
82      * Constructs a <code>ClassNotFoundException</code> with the
83      * specified detail message and optional exception that was
84      * raised while loading the class.
85      *
86      * @param s the detail message
87      * @param ex the exception that was raised while loading the class
88      * @since 1.2
89      */
ClassNotFoundException(String s, Throwable ex)90     public ClassNotFoundException(String s, Throwable ex) {
91         super(s, ex);  //  Disallow initCause
92     }
93 
94     /**
95      * Returns the exception that was raised if an error occurred while
96      * attempting to load the class. Otherwise, returns {@code null}.
97      *
98      * <p>This method predates the general-purpose exception chaining facility.
99      * The {@link Throwable#getCause()} method is now the preferred means of
100      * obtaining this information.
101      *
102      * @return the <code>Exception</code> that was raised while loading a class
103      * @since 1.2
104      */
getException()105     public Throwable getException() {
106         return super.getCause();
107     }
108 
109     /**
110      * Serializable fields for ClassNotFoundException.
111      *
112      * @serialField ex Throwable
113      */
114     private static final ObjectStreamField[] serialPersistentFields = {
115         new ObjectStreamField("ex", Throwable.class)
116     };
117 
118     /*
119      * Reconstitutes the ClassNotFoundException instance from a stream
120      * and initialize the cause properly when deserializing from an older
121      * version.
122      *
123      * The getException and getCause method returns the private "ex" field
124      * in the older implementation and ClassNotFoundException::cause
125      * was set to null.
126      */
readObject(ObjectInputStream s)127     private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
128         ObjectInputStream.GetField fields = s.readFields();
129         Throwable exception = (Throwable) fields.get("ex", null);
130         if (exception != null) {
131             setCause(exception);
132         }
133     }
134 
135     /*
136      * To maintain compatibility with older implementation, write a serial
137      * "ex" field with the cause as the value.
138      */
writeObject(ObjectOutputStream out)139     private void writeObject(ObjectOutputStream out) throws IOException {
140         ObjectOutputStream.PutField fields = out.putFields();
141         fields.put("ex", super.getCause());
142         out.writeFields();
143     }
144 }
145