1 ---

     2 # Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.

     3 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4 #

     5 # This code is free software; you can redistribute it and/or modify it

     6 # under the terms of the GNU General Public License version 2 only, as

     7 # published by the Free Software Foundation.

     8 #

     9 # This code is distributed in the hope that it will be useful, but WITHOUT

    10 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11 # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12 # version 2 for more details (a copy is included in the LICENSE file that

    13 # accompanied this code).

    14 #

    15 # You should have received a copy of the GNU General Public License version

    16 # 2 along with this work; if not, write to the Free Software Foundation,

    17 # Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18 #

    19 # Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20 # or visit www.oracle.com if you need additional information or have any

    21 # questions.

    22 

    23 include-before: '[CONTENTS](index.html) | [PREV](exceptions.html) | NEXT'

    24 include-after: '[CONTENTS](index.html) | [PREV](exceptions.html) | NEXT'

    25 

    26 title: 'Java Object Serialization Specification: C - Example of Serializable Fields'

    27 ---

    28 

    29 -   [Example Alternate Implementation of

    30     java.io.File](#c.1-example-alternate-implementation-of-java.io.file)

    31 

    32 -------------------------------------------------------------------------------

    33 

    34 ## C.1 Example Alternate Implementation of java.io.File

    35 

    36 This appendix provides a brief example of how an existing class could be

    37 specified and implemented to interoperate with the existing implementation but

    38 without requiring the same assumptions about the representation of the file

    39 name as a *String*.

    40 

    41 The system class `java.io.File` represents a filename and has methods for

    42 parsing, manipulating files and directories by name. It has a single private

    43 field that contains the current file name. The semantics of the methods that

    44 parse paths depend on the current path separator which is held in a static

    45 field. This path separator is part of the serialized state of a file so that

    46 file name can be adjusted when read.

    47 

    48 The serialized state of a `File` object is defined as the serializable fields

    49 and the sequence of data values for the file. In this case, there is one of

    50 each.

    51 

    52 ```

    53 Serializable Fields:

    54     String path;     // path name with embedded separators

    55 Serializable Data:

    56     char            // path name separator for path name

    57 ```

    58 

    59 An alternate implementation might be defined as follows:

    60 

    61 ```

    62 class File implements java.io.Serializable {

    63     ...

    64     private String[] pathcomponents;

    65     // Define serializable fields with the ObjectStreamClass

    66 

    67     /**

    68      * @serialField path String

    69      *              Path components separated by separator.

    70      */

    71 

    72     private static final ObjectStreamField[] serialPersistentFields

    73         = { new ObjectStreamField("path", String.class) };

    74     ...

    75         /**

    76          * @serialData  Default fields followed by separator character.

    77          */

    78 

    79     private void writeObject(ObjectOutputStream s)

    80         throws IOException

    81     {

    82         ObjectOutputStream.PutField fields = s.putFields();

    83         StringBuffer str = new StringBuffer();

    84         for(int i = 0; i < pathcomponents; i++) {

    85             str.append(separator);

    86             str.append(pathcomponents[i]);

    87         }

    88         fields.put("path", str.toString());

    89         s.writeFields();

    90         s.writeChar(separatorChar); // Add the separator character

    91     }

    92     ...

    93 

    94     private void readObject(ObjectInputStream s)

    95         throws IOException

    96     {

    97         ObjectInputStream.GetField fields = s.readFields();

    98         String path = (String)fields.get("path", null);

    99         ...

   100         char sep = s.readChar(); // read the previous separator char

   101 

   102         // parse path into components using the separator

   103         // and store into pathcomponents array.

   104     }

   105 }

   106 ```

   107 

   108 -------------------------------------------------------------------------------

   109 

   110 *[Copyright](../../../legal/SMICopyright.html) © 2005, 2017, Oracle

   111 and/or its affiliates. All rights reserved.*