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1
23
24 package com.sun.enterprise.admin.common.domains.registry;
25
26 import java.io.RandomAccessFile  ;
27 import java.lang.ClassNotFoundException ;
28 import java.io.IOException ;
29 import java.io.ObjectInputStream ;
30 import java.nio.channels.FileChannel ;
31 import java.nio.channels.FileLock ;
32 import java.io.FileInputStream ;
33 import java.io.EOFException ;
34
35
36 class Unlocked implements LockingStore
37 {
38
39 private PersistentStore storeImpl;
40
41 Unlocked(PersistentStore s){
42 if (s == null) {
43 throw new NullPointerException ("store is null");
44 }
45
46 storeImpl = s;
47 }
48
49 public synchronized Object readObject() throws IOException , TimeoutException, ClassNotFoundException {
50 ObjectInputStream in = null;
51 Object o = null;
52 try{
53 in = getIn();
54 o = (in != null ? in.readObject() : null) ;
55 }
56 catch (EOFException e){
57 o = null; }
59 finally {
60 if (in != null) {
61 in.close();
62 }
63 }
64 return o;
65 }
66
67 public long lastModified(){ return 0L ;}
68 public void unlock(){}
69
70
71 public void writeObject(Object o) throws IllegalStateException , IOException , TimeoutException {
72 throw new IllegalStateException ("Unlocked state - writeObject() not allowed");
73
74 }
75
76 public void lock() throws TimeoutException, IOException {
77 final RandomAccessFile raf = new RandomAccessFile (storeImpl.getLock(),
78 "rws");
79 getWriteLock(raf.getChannel());
80 storeImpl.setState(new Locked(storeImpl, raf));
81 }
82
83 private ObjectInputStream getIn() throws IOException {
84 final FileInputStream fis = new FileInputStream (storeImpl.getStore());
85 getReadLock(fis.getChannel());
86 if (fis.available() > 0){
87 return new ObjectInputStream (fis);
88 } else {
89 fis.close();
90 return null;
91 }
92 }
93
94 private FileLock getReadLock(FileChannel ch) throws TimeoutException, IOException {
95 return obtainLock(ch, true);
96 }
97
98
101 private FileLock getWriteLock(FileChannel ch) throws TimeoutException, IOException {
102 return obtainLock(ch, false);
103 }
104
105 private FileLock obtainLock(FileChannel channel, boolean shared) throws TimeoutException, IOException {
106 FileLock lock = null;
107 int attempts = 0;
108 try{
109
110 while ((lock = channel.tryLock(0L, 0x7fffffff, shared)) == null && attempts++ < ATTEMPTS){
111 Thread.currentThread().sleep(TIMEOUT);
112 }
113 }
114 catch (InterruptedException e){
115 throw new TimeoutException();
116 }
117
118 if (lock == null) {
119 throw new TimeoutException();
120 }
121 return lock;
122 }
123
124 private static final int TIMEOUT = 3;
128
129 private static final int ATTEMPTS = 50;
131
132 }
133
134
135
136 |
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