1 package org.apache.ojb.broker.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 /**
19 * This interface defines the lock isolation level constants used by
20 * OJB locking api. It contains numeric constants and literal constants
21 * representing all known isolation levels.
22 * <p/>
23 * NOTE: The lock isolation levels are labeled like the database transaction level but
24 * the definition of the levels is different - take care of that.
25 *
26 * @version $Id: IsolationLevels.java,v 1.1 2007-08-24 22:17:41 ewestfal Exp $
27 */
28 public interface IsolationLevels
29 {
30 /**
31 * Numeric constant representing an no-op isolation level.
32 * <p/>
33 * The lock manager completely ignores locking.
34 * <p/>
35 * Allows:<br/>
36 * all possible concurrent side-effects<br/>
37 */
38 public final static int IL_NONE = -1;
39
40 /**
41 * Numeric constant representing the uncommited read isolation level.
42 * <p/>
43 * Obtaining two concurrent write locks on a given object is not
44 * allowed. Obtaining read locks is allowed even if
45 * another transaction is writing to that object
46 * (Thats why this level is also called "dirty reads").
47 * <p/>
48 * Allows:<br/>
49 * Dirty Reads<br/>
50 * Non-Repeatable Reads<br/>
51 * Phantom Reads<br/>
52 */
53 public final static int IL_READ_UNCOMMITTED = 2;
54
55 /**
56 * Numeric constant representing the commited read isolation level.
57 * <p/>
58 * Obtaining two concurrent write locks on a given object is not allowed.
59 * Obtaining read locks is allowed only if there is no write lock on
60 * the given object.
61 * <p/>
62 * Allows:<br/>
63 * Non-Repeatable Reads<br/>
64 * Phantom Reads<br/>
65 */
66 public final static int IL_READ_COMMITTED = 3;
67
68 /**
69 * Numeric constant representing the repeatable read isolation level.
70 * <p/>
71 * As commited reads, but obtaining a write lock on an object that has
72 * been locked for reading by another transaction is not allowed.
73 * <p/>
74 * Allows:<br/>
75 * Phantom Reads<br/>
76 */
77 public final static int IL_REPEATABLE_READ = 5;
78
79 /**
80 * Numeric constant representing the serializable transactions isolation level.
81 * <p/>
82 * As Repeatable Reads, but it is even not allowed to have multiple
83 * read locks on a given object.
84 * <p/>
85 * Allows:<br/>
86 * -<br/>
87 */
88 public final static int IL_SERIALIZABLE = 7;
89
90 /**
91 * Numeric constant representing the optimistic locking isolation level.
92 * <p/>
93 * The lock manager does not perform any pessimistic locking action. Normally
94 * it's not needed to declare this isolation level in persistent object metadata,
95 * because OJB will automatically detect an enabled optimistic locking.
96 * <br/>
97 * NOTE: Usage of this isolation level needs an specific optimistic locking
98 * declaration for the specified object. This declaration is <strong>not</strong>
99 * automatically handled by OJB and need setting of configuration properties - see OJB docs.
100 */
101 public final static int IL_OPTIMISTIC = 4;
102
103 /**
104 * Numeric constant representing the default isolation level used by
105 * OJB - current used default level is {@link #IL_READ_UNCOMMITTED}.
106 */
107 public final static int IL_DEFAULT = IL_READ_UNCOMMITTED;
108
109 /**
110 * Literal constant representing the uncommited read isolation level.
111 */
112 public final static String LITERAL_IL_NONE = "none";
113
114 /**
115 * Literal constant representing the uncommited read isolation level.
116 */
117 public final static String LITERAL_IL_READ_UNCOMMITTED = "read-uncommitted";
118
119 /**
120 * Literal constant representing the commited read isolation level.
121 */
122 public final static String LITERAL_IL_READ_COMMITTED = "read-committed";
123
124 /**
125 * Literal constant representing the repeatable read isolation level.
126 */
127 public final static String LITERAL_IL_REPEATABLE_READ = "repeatable-read";
128
129 /**
130 * Literal constant representing the serializable transactions isolation level.
131 */
132 public final static String LITERAL_IL_SERIALIZABLE = "serializable";
133
134 /**
135 * Literal constant representing the optimistic locking isolation level.
136 */
137 public final static String LITERAL_IL_OPTIMISTIC = "optimistic";
138 }