LockManager


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  import org.apache.ojb.broker.Identity;
20  
21  /**
22   * This interface declares the functionality of the OJB internal Locking mechanism.
23   * A default implementaion LockManagerDefaultImpl is provided. This implementaion
24   * keeps distributed locks in the database. The locking mechanisms thus involves a
25   * lot of database lookups and writes. For some environments this solution may not
26   * be adequate. OJB allows to provide user defined implementations of this interface.
27   * To activate a user defined LockManagerDefaultImpl it must be configured in the OJB.properties file.
28   *
29   *
30   * @author thma
31   */
32  public interface LockManager
33  {
34      /**
35       * aquires a readlock for transaction tx on object obj.
36       * Returns true if successful, else false.
37       */
38      public abstract boolean readLock(TransactionImpl tx, Object   obj);
39  
40      /**
41       * aquires a readlock for transaction tx on object obj.
42       * Returns true if successful, else false.
43       */
44      public abstract boolean readLock(TransactionImpl tx, Identity oid, Object   obj);
45  
46  
47      /**
48       * aquires a writelock for transaction tx on object obj.
49       * Returns true if successful, else false.
50       */
51      public abstract boolean writeLock(TransactionImpl tx, Object   obj);
52  
53      /**
54       * aquires a writelock for transaction tx on object obj.
55       * Returns true if successful, else false.
56       */
57      public abstract boolean writeLock(TransactionImpl tx, Identity oid, Object   obj);
58  
59  
60      /**
61       * upgrades readlock for transaction tx on object obj to a writelock.
62       * If no readlock existed a writelock is acquired anyway.
63       * Returns true if successful, else false.
64       */
65      public abstract boolean upgradeLock(TransactionImpl tx, Object   obj);
66  
67      /**
68       * upgrades readlock for transaction tx on object obj to a writelock.
69       * If no readlock existed a writelock is acquired anyway.
70       * Returns true if successful, else false.
71       */
72      public abstract boolean upgradeLock(TransactionImpl tx, Identity oid, Object   obj);
73  
74  
75      /**
76       * releases a lock for transaction tx on object obj.
77       * Returns true if successful, else false.
78       */
79      public abstract boolean releaseLock(TransactionImpl tx, Object   obj);
80  
81      /**
82       * releases a lock for transaction tx on object obj.
83       * Returns true if successful, else false.
84       */
85      public abstract boolean releaseLock(TransactionImpl tx, Identity oid, Object   obj);
86  
87  
88      /**
89       * checks if there is a readlock for transaction tx on object obj.
90       * Returns true if so, else false.
91       */
92      public abstract boolean checkRead(TransactionImpl tx, Object   obj);
93  
94      /**
95       * checks if there is a readlock for transaction tx on object obj.
96       * Returns true if so, else false.
97       */
98      public abstract boolean checkRead(TransactionImpl tx, Identity oid, Object   obj);
99  
100 
101     /**
102      * checks if there is a writelock for transaction tx on object obj.
103      * Returns true if so, else false.
104      */
105     public abstract boolean checkWrite(TransactionImpl tx, Object   obj);
106 
107     /**
108      * checks if there is a writelock for transaction tx on object obj.
109      * Returns true if so, else false.
110      */
111     public abstract boolean checkWrite(TransactionImpl tx, Identity oid, Object   obj);
112 }
113
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