AutoResetObjectOutputStream


1   /***************************************
2    *                                     *
3    *  JBoss: The OpenSource J2EE WebOS   *
4    *                                     *
5    *  Distributable under LGPL license.  *
6    *  See terms of license at gnu.org.   *
7    *                                     *
8    ***************************************/
9   
10  package org.jboss.util.stream;
11  
12  import java.io.ObjectOutputStream  ;
13  import java.io.IOException  ;
14  
15  /**
16   * An <code>ObjectOutputStream</code> that will auto reset after <i>n</i>
17   * objects have been written to the underlying stream.
18   *
19   * <h3>Concurrency</h3>
20   * This class is <b>not</b> synchronized.
21   *
22   * @version <tt>$Revision: 1.1 $</tt>
23   * @author  <a HREF="mailto:jason@planet57.com">Jason Dillon</a>
24   */
25  public class AutoResetObjectOutputStream
26     extends ObjectOutputStreamAdapter
27  {
28     /** Number of objects to write before resetting. */
29     protected int after; // = 0
30  
31     /** Number of objects written so far. */
32     protected int count; // = 0
33  
34     /**
35      * Construct a new AutoResetObjectOutputStream.
36      *
37      * @param out     An ObjectOutputStream stream.
38      * @param after   Number of objects to write before resetting.
39      *
40      * @throws IllegalArgumentException    After <= 0
41      * @throws IOException                 Any exception thrown by
42      *                                     the underlying OutputStream.
43      */
44     public AutoResetObjectOutputStream(ObjectOutputStream   out, int after)
45        throws IOException   
46     {
47        super(out);
48  
49        setResetAfter(after);
50     }
51  
52     /**
53      * Set the number of objects that must be written before resetting
54      * the stream.
55      *
56      * @param after   Number of objects to write before resetting.
57      *
58      * @throws IllegalArgumentException    After <= 0
59      */
60     public void setResetAfter(int after) {
61        if (after <= 0)
62           throw new IllegalArgumentException  ("after <= 0");
63  
64        this.after = after;
65     }
66  
67     /**
68      * Get the number of objects that must be written before resetting
69      * the stream.
70      *
71      * @return  Number of objects to write before resetting.
72      */
73     public final int getResetAfter() {
74        return after;
75     }
76  
77     /**
78      * Get the number of objects written to the stream so far.
79      *
80      * @return  The number of objects written to the stream so far.
81      */
82     public final int getCount() {
83        return count;
84     }
85  
86     /**
87      * Write the given object and reset if the number of objects written
88      * (including this one) exceeds the after count.
89      *
90      * @param obj     Object to write.
91      *
92      * @throws IOException  Any exception thrown by the underlying stream.
93      */
94     protected void writeObjectOverride(Object   obj) throws IOException   {
95        super.writeObjectOverride(obj);
96        count++;
97  
98        if (count >= after) {
99           reset();
100       }
101    }
102 
103    /**
104     * Resets the object counter as well as the nested stream.
105     *
106     * @throws IOException
107     */
108    public void reset() throws IOException   {
109       out.reset();
110       count = 0;
111    }
112 }
113
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