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Java > Open Source Codes > org > archive > crawler > frontier > RecyclingSerialBinding


1 /* RecyclingSerialBinding
2 *
3 * $Id: RecyclingSerialBinding.java,v 1.1.16.1 2007/01/13 01:31:23 stack-sf Exp $
4 *
5 * Created on May 25, 2005
6 *
7 * Copyright (C) 2005 Internet Archive.
8 *
9 * This file is part of the Heritrix web crawler (crawler.archive.org).
10 *
11 * Heritrix is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU Lesser Public License as published by
13 * the Free Software Foundation; either version 2.1 of the License, or
14 * any later version.
15 *
16 * Heritrix is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser Public License
22 * along with Heritrix; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 */
25 package org.archive.crawler.frontier;
26
27 import java.io.IOException JavaDoc;
28
29 import com.sleepycat.bind.serial.ClassCatalog;
30 import com.sleepycat.bind.serial.SerialBinding;
31 import com.sleepycat.bind.serial.SerialOutput;
32 import com.sleepycat.je.DatabaseEntry;
33 import com.sleepycat.util.FastOutputStream;
34 import com.sleepycat.util.RuntimeExceptionWrapper;
35
36 /**
37  * A SerialBinding that recycles a single FastOutputStream per
38  * thread, avoiding reallocation of the internal buffer for
39  * either repeated serializations or because of mid-serialization
40  * expansions. (Cached stream's buffer will quickly grow to a size
41  * sufficient for all serialized instances.)
42  *
43  * @author gojomo
44  */
45 public class RecyclingSerialBinding extends SerialBinding {
46     /**
47      * Thread-local cache of reusable FastOutputStream
48      */
49     ThreadLocal JavaDoc<FastOutputStream> fastOutputStreamHolder
50      = new ThreadLocal JavaDoc<FastOutputStream>();
51     
52     private ClassCatalog classCatalog;
53     private Class JavaDoc baseClass;
54
55     /**
56      * Constructor. Save parameters locally, as superclass
57      * fields are private.
58      *
59      * @param classCatalog is the catalog to hold shared class information
60      *
61      * @param baseClass is the base class for serialized objects stored using
62      * this binding
63      */
64     public RecyclingSerialBinding(ClassCatalog classCatalog, Class JavaDoc baseClass) {
65         super(classCatalog, baseClass);
66         this.classCatalog = classCatalog;
67         this.baseClass = baseClass;
68     }
69
70     /**
71      * Copies superclass simply to allow different source for FastOoutputStream.
72      *
73      * @see com.sleepycat.bind.serial.SerialBinding#entryToObject
74      */
75     public void objectToEntry(Object JavaDoc object, DatabaseEntry entry) {
76
77         if (baseClass != null && !baseClass.isInstance(object)) {
78             throw new IllegalArgumentException JavaDoc(
79                         "Data object class (" + object.getClass() +
80                         ") not an instance of binding's base class (" +
81                         baseClass + ')');
82         }
83         FastOutputStream fo = getFastOutputStream();
84         try {
85             SerialOutput jos = new SerialOutput(fo, classCatalog);
86             jos.writeObject(object);
87         } catch (IOException JavaDoc e) {
88             throw new RuntimeExceptionWrapper(e);
89         }
90
91         byte[] hdr = SerialOutput.getStreamHeader();
92         entry.setData(fo.getBufferBytes(), hdr.length,
93                      fo.getBufferLength() - hdr.length);
94     }
95
96     /**
97      * Get the cached (and likely pre-grown to efficient size) FastOutputStream,
98      * creating it if necessary.
99      *
100      * @return FastOutputStream
101      */
102     private FastOutputStream getFastOutputStream() {
103         FastOutputStream fo = (FastOutputStream) fastOutputStreamHolder.get();
104         if (fo == null) {
105             fo = new FastOutputStream();
106             fastOutputStreamHolder.set(fo);
107         }
108         fo.reset();
109         return fo;
110     }
111 }
112
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