Coverage Report

Coverage Report - org.apache.ojb.odmg.locking.RepeatableReadStrategy

Classes in this File

7.5

 package org.apache.ojb.odmg.locking;
 
 /* Copyright 2002-2005 The Apache Software Foundation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 import org.apache.ojb.odmg.TransactionImpl;
 
 import java.util.Collection;
 
 /**
  * The implementation of the Repeatable Reads Locking strategy.
  * Locks are obtained for reading and modifying the database.
  * Locks on all modified objects are held until EOT.
  * Locks obtained for reading data are held until EOT.
  * Allows:
  * Phantom Reads
  *
  * @author Thomas Mahler & David Dixon-Peugh
  */
 public class RepeatableReadStrategy extends AbstractLockStrategy
 {
     /**
      * acquire a read lock on Object obj for Transaction tx.
      * @param tx the transaction requesting the lock
      * @param obj the Object to be locked
      * @return true if successful, else false
      *
      */
     public boolean readLock(TransactionImpl tx, Object obj)
     {
         LockEntry writer = getWriter(obj);
         if (writer == null)
         {
             if (addReader(tx, obj))
                 return true;
             else
                 return readLock(tx, obj);
         }
         if (writer.isOwnedBy(tx))
         {
             return true;    // If I'm the writer, I can read.
         }
         else
             return false;
 
     }
 
     /**
      * acquire a write lock on Object obj for Transaction tx.
      * @param tx the transaction requesting the lock
      * @param obj the Object to be locked
      * @return true if successful, else false
      *
      */
     public boolean writeLock(TransactionImpl tx, Object obj)
     {
         LockEntry writer = getWriter(obj);
         Collection readers = getReaders(obj);
         if (writer == null)
         {
             if (readers.size() == 0)
             {
                 if (setWriter(tx, obj))
                     return true;
                 else
                     return writeLock(tx, obj);
             }
 
             else if (readers.size() == 1)
             {
                 if (((LockEntry) readers.iterator().next()).isOwnedBy(tx))
                     return upgradeLock(tx, obj);
             }
         }
         else if (writer.isOwnedBy(tx))
         {
             return true;    // If I'm the writer, then I can write.
         }
         return false;
     }
 
 
     /**
      * acquire a lock upgrade (from read to write) lock on Object obj for Transaction tx.
      * @param tx the transaction requesting the lock
      * @param obj the Object to be locked
      * @return true if successful, else false
      *
      */
     public boolean upgradeLock(TransactionImpl tx, Object obj)
     {
         LockEntry writer = getWriter(obj);
         if (writer == null)
         {
             Collection readers = this.getReaders(obj);
             if (readers.size() == 1)
             {
                 LockEntry reader = (LockEntry) readers.iterator().next();
                 if (reader.isOwnedBy(tx))
                 {
                     if (upgradeLock(reader))
                         return true;
                     else
                         return upgradeLock(tx, obj);
                 }
             }
             else if (readers.size() == 0)
             {
                 if (setWriter(tx, obj))
                     return true;
                 else
                     return upgradeLock(tx, obj);
             }
 
 
         }
         else if (writer.isOwnedBy(tx))
         {
             return true;    // If I already have Write, then I've upgraded.
         }
 
         return false;
     }
 
     /**
      * release a lock on Object obj for Transaction tx.
      * @param tx the transaction releasing the lock
      * @param obj the Object to be unlocked
      * @return true if successful, else false
      *
      */
     public boolean releaseLock(TransactionImpl tx, Object obj)
     {
         LockEntry writer = getWriter(obj);
         if (writer != null && writer.isOwnedBy(tx))
         {
             removeWriter(writer);
             return true;
         }
         if (hasReadLock(tx, obj))
         {
             removeReader(tx, obj);
             return true;
         }
         return false;
     }
 
     /**
      * checks whether the specified Object obj is read-locked by Transaction tx.
      * @param tx the transaction
      * @param obj the Object to be checked
      * @return true if lock exists, else false
      */
     public boolean checkRead(TransactionImpl tx, Object obj)
     {
         if (hasReadLock(tx, obj))
         {
             return true;
         }
         LockEntry writer = getWriter(obj);
         if (writer != null && writer.isOwnedBy(tx))
         {
             return true;
         }
         else
             return false;
     }
 
     /**
      * checks whether the specified Object obj is write-locked by Transaction tx.
      * @param tx the transaction
      * @param obj the Object to be checked
      * @return true if lock exists, else false
      */
     public boolean checkWrite(TransactionImpl tx, Object obj)
     {
         LockEntry writer = getWriter(obj);
         return (writer != null && writer.isOwnedBy(tx));
     }
 }

1		package org.apache.ojb.odmg.locking;
2
3		/* Copyright 2002-2005 The Apache Software Foundation
4		*
5		* Licensed under the Apache License, Version 2.0 (the "License");
6		* you may not use this file except in compliance with the License.
7		* 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		import org.apache.ojb.odmg.TransactionImpl;
19
20		import java.util.Collection;
21
22		/**
23		* The implementation of the Repeatable Reads Locking strategy.
24		* Locks are obtained for reading and modifying the database.
25		* Locks on all modified objects are held until EOT.
26		* Locks obtained for reading data are held until EOT.
27		* Allows:
28		* Phantom Reads
29		*
30		* @author Thomas Mahler & David Dixon-Peugh
31		*/
32		public class RepeatableReadStrategy extends AbstractLockStrategy
33		{
34		/**
35		* acquire a read lock on Object obj for Transaction tx.
36		* @param tx the transaction requesting the lock
37		* @param obj the Object to be locked
38		* @return true if successful, else false
39		*
40		*/
41		public boolean readLock(TransactionImpl tx, Object obj)
42		{
43		LockEntry writer = getWriter(obj);
44		if (writer == null)
45		{
46		if (addReader(tx, obj))
47		return true;
48		else
49		return readLock(tx, obj);
50		}
51		if (writer.isOwnedBy(tx))
52		{
53		return true; // If I'm the writer, I can read.
54		}
55		else
56		return false;
57
58		}
59
60		/**
61		* acquire a write lock on Object obj for Transaction tx.
62		* @param tx the transaction requesting the lock
63		* @param obj the Object to be locked
64		* @return true if successful, else false
65		*
66		*/
67		public boolean writeLock(TransactionImpl tx, Object obj)
68		{
69		LockEntry writer = getWriter(obj);
70		Collection readers = getReaders(obj);
71		if (writer == null)
72		{
73		if (readers.size() == 0)
74		{
75		if (setWriter(tx, obj))
76		return true;
77		else
78		return writeLock(tx, obj);
79		}
80
81		else if (readers.size() == 1)
82		{
83		if (((LockEntry) readers.iterator().next()).isOwnedBy(tx))
84		return upgradeLock(tx, obj);
85		}
86		}
87		else if (writer.isOwnedBy(tx))
88		{
89		return true; // If I'm the writer, then I can write.
90		}
91		return false;
92		}
93
94
95		/**
96		* acquire a lock upgrade (from read to write) lock on Object obj for Transaction tx.
97		* @param tx the transaction requesting the lock
98		* @param obj the Object to be locked
99		* @return true if successful, else false
100		*
101		*/
102		public boolean upgradeLock(TransactionImpl tx, Object obj)
103		{
104		LockEntry writer = getWriter(obj);
105		if (writer == null)
106		{
107		Collection readers = this.getReaders(obj);
108		if (readers.size() == 1)
109		{
110		LockEntry reader = (LockEntry) readers.iterator().next();
111		if (reader.isOwnedBy(tx))
112		{
113		if (upgradeLock(reader))
114		return true;
115		else
116		return upgradeLock(tx, obj);
117		}
118		}
119		else if (readers.size() == 0)
120		{
121		if (setWriter(tx, obj))
122		return true;
123		else
124		return upgradeLock(tx, obj);
125		}
126
127
128		}
129		else if (writer.isOwnedBy(tx))
130		{
131		return true; // If I already have Write, then I've upgraded.
132		}
133
134		return false;
135		}
136
137		/**
138		* release a lock on Object obj for Transaction tx.
139		* @param tx the transaction releasing the lock
140		* @param obj the Object to be unlocked
141		* @return true if successful, else false
142		*
143		*/
144		public boolean releaseLock(TransactionImpl tx, Object obj)
145		{
146		LockEntry writer = getWriter(obj);
147		if (writer != null && writer.isOwnedBy(tx))
148		{
149		removeWriter(writer);
150		return true;
151		}
152		if (hasReadLock(tx, obj))
153		{
154		removeReader(tx, obj);
155		return true;
156		}
157		return false;
158		}
159
160		/**
161		* checks whether the specified Object obj is read-locked by Transaction tx.
162		* @param tx the transaction
163		* @param obj the Object to be checked
164		* @return true if lock exists, else false
165		*/
166		public boolean checkRead(TransactionImpl tx, Object obj)
167		{
168		if (hasReadLock(tx, obj))
169		{
170		return true;
171		}
172		LockEntry writer = getWriter(obj);
173		if (writer != null && writer.isOwnedBy(tx))
174		{
175		return true;
176		}
177		else
178		return false;
179		}
180
181		/**
182		* checks whether the specified Object obj is write-locked by Transaction tx.
183		* @param tx the transaction
184		* @param obj the Object to be checked
185		* @return true if lock exists, else false
186		*/
187		public boolean checkWrite(TransactionImpl tx, Object obj)
188		{
189		LockEntry writer = getWriter(obj);
190		return (writer != null && writer.isOwnedBy(tx));
191		}
192		}