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Java > Open Source Codes > org > apache > jasper > runtime > PerThreadTagHandlerPool


1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements. See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License. You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17
18 package org.apache.jasper.runtime;
19
20 import java.util.Enumeration JavaDoc;
21 import java.util.Vector JavaDoc;
22
23 import javax.servlet.ServletConfig JavaDoc;
24 import javax.servlet.jsp.JspException JavaDoc;
25 import javax.servlet.jsp.tagext.Tag JavaDoc;
26
27 import org.apache.jasper.Constants;
28
29 /**
30  * Thread-local based pool of tag handlers that can be reused.
31  *
32  * @author Jan Luehe
33  * @author Costin Manolache
34  */
35 public class PerThreadTagHandlerPool extends TagHandlerPool {
36
37     private int maxSize;
38
39     // For cleanup
40 private Vector JavaDoc perThreadDataVector;
41
42     private ThreadLocal JavaDoc perThread;
43
44     private static class PerThreadData {
45         Tag JavaDoc handlers[];
46         int current;
47     }
48
49     /**
50      * Constructs a tag handler pool with the default capacity.
51      */
52     public PerThreadTagHandlerPool() {
53         super();
54         perThreadDataVector = new Vector JavaDoc();
55     }
56
57     protected void init(ServletConfig JavaDoc config) {
58         maxSize = Constants.MAX_POOL_SIZE;
59         String JavaDoc maxSizeS = getOption(config, OPTION_MAXSIZE, null);
60         if (maxSizeS != null) {
61             maxSize = Integer.parseInt(maxSizeS);
62             if (maxSize < 0) {
63                 maxSize = Constants.MAX_POOL_SIZE;
64             }
65         }
66
67         perThread = new ThreadLocal JavaDoc() {
68             protected Object JavaDoc initialValue() {
69                 PerThreadData ptd = new PerThreadData();
70                 ptd.handlers = new Tag JavaDoc[maxSize];
71                 ptd.current = -1;
72                 perThreadDataVector.addElement(ptd);
73                 return ptd;
74             }
75         };
76     }
77
78     /**
79      * Gets the next available tag handler from this tag handler pool,
80      * instantiating one if this tag handler pool is empty.
81      *
82      * @param handlerClass Tag handler class
83      *
84      * @return Reused or newly instantiated tag handler
85      *
86      * @throws JspException if a tag handler cannot be instantiated
87      */
88     public Tag JavaDoc get(Class JavaDoc handlerClass) throws JspException JavaDoc {
89         PerThreadData ptd = (PerThreadData)perThread.get();
90         if(ptd.current >=0 ) {
91             return ptd.handlers[ptd.current--];
92         } else {
93         try {
94         return (Tag JavaDoc) handlerClass.newInstance();
95         } catch (Exception JavaDoc e) {
96         throw new JspException JavaDoc(e.getMessage(), e);
97         }
98     }
99     }
100
101     /**
102      * Adds the given tag handler to this tag handler pool, unless this tag
103      * handler pool has already reached its capacity, in which case the tag
104      * handler's release() method is called.
105      *
106      * @param handler Tag handler to add to this tag handler pool
107      */
108     public void reuse(Tag JavaDoc handler) {
109         PerThreadData ptd=(PerThreadData)perThread.get();
110     if (ptd.current < (ptd.handlers.length - 1)) {
111         ptd.handlers[++ptd.current] = handler;
112         } else {
113             handler.release();
114         }
115     }
116
117     /**
118      * Calls the release() method of all tag handlers in this tag handler pool.
119      */
120     public void release() {
121         Enumeration JavaDoc enumeration = perThreadDataVector.elements();
122         while (enumeration.hasMoreElements()) {
123         PerThreadData ptd = (PerThreadData)enumeration.nextElement();
124             if (ptd.handlers != null) {
125                 for (int i=ptd.current; i>=0; i--) {
126                     if (ptd.handlers[i] != null) {
127                         ptd.handlers[i].release();
128             }
129                 }
130             }
131         }
132     }
133 }
134
135
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