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| 33 | PointedEar | 1 | /* |
| 2 | * Hibernate, Relational Persistence for Idiomatic Java |
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| 3 | * |
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| 4 | * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as |
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| 5 | * indicated by the @author tags or express copyright attribution |
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| 6 | * statements applied by the authors. All third-party contributions are |
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| 7 | * distributed under license by Red Hat Middleware LLC. |
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| 8 | * |
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| 9 | * This copyrighted material is made available to anyone wishing to use, modify, |
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| 10 | * copy, or redistribute it subject to the terms and conditions of the GNU |
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| 11 | * Lesser General Public License, as published by the Free Software Foundation. |
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| 12 | * |
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| 13 | * This program is distributed in the hope that it will be useful, |
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| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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| 15 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License |
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| 16 | * for more details. |
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| 17 | * |
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| 18 | * You should have received a copy of the GNU Lesser General Public License |
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| 19 | * along with this distribution; if not, write to: |
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| 20 | * Free Software Foundation, Inc. |
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| 21 | * 51 Franklin Street, Fifth Floor |
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| 22 | * Boston, MA 02110-1301 USA |
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| 23 | * |
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| 24 | */ |
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| 25 | package org.hibernate; |
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| 26 | |||
| 27 | import java.io.Serializable; |
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| 28 | import java.util.HashMap; |
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| 29 | import java.util.Map; |
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| 30 | |||
| 31 | /** |
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| 32 | * Instances represent a lock mode for a row of a relational |
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| 33 | * database table. It is not intended that users spend much |
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| 34 | * time worrying about locking since Hibernate usually |
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| 35 | * obtains exactly the right lock level automatically. |
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| 36 | * Some "advanced" users may wish to explicitly specify lock |
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| 37 | * levels. |
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| 38 | * |
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| 39 | * @see Session#lock(Object,LockMode) |
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| 40 | * @author Gavin King |
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| 41 | */ |
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| 42 | public final class LockMode implements Serializable { |
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| 43 | private final int level; |
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| 44 | private final String name; |
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| 45 | private static final Map INSTANCES = new HashMap(); |
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| 46 | |||
| 47 | private LockMode(int level, String name) { |
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| 48 | this.level=level; |
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| 49 | this.name=name; |
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| 50 | } |
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| 51 | public String toString() { |
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| 52 | return name; |
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| 53 | } |
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| 54 | /** |
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| 55 | * Check if this lock mode is more restrictive than the given lock mode. |
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| 56 | * |
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| 57 | * @param mode LockMode to check |
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| 58 | * @return true if this lock mode is more restrictive than given lock mode |
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| 59 | */ |
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| 60 | public boolean greaterThan(LockMode mode) { |
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| 61 | return level > mode.level; |
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| 62 | } |
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| 63 | /** |
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| 64 | * Check if this lock mode is less restrictive than the given lock mode. |
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| 65 | * |
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| 66 | * @param mode LockMode to check |
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| 67 | * @return true if this lock mode is less restrictive than given lock mode |
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| 68 | */ |
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| 69 | public boolean lessThan(LockMode mode) { |
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| 70 | return level < mode.level; |
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| 71 | } |
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| 72 | /** |
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| 73 | * No lock required. If an object is requested with this lock |
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| 74 | * mode, a <tt>READ</tt> lock will be obtained if it is |
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| 75 | * necessary to actually read the state from the database, |
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| 76 | * rather than pull it from a cache.<br> |
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| 77 | * <br> |
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| 78 | * This is the "default" lock mode. |
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| 79 | */ |
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| 80 | public static final LockMode NONE = new LockMode(0, "NONE"); |
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| 81 | /** |
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| 82 | * A shared lock. Objects in this lock mode were read from |
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| 83 | * the database in the current transaction, rather than being |
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| 84 | * pulled from a cache. |
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| 85 | */ |
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| 86 | public static final LockMode READ = new LockMode(5, "READ"); |
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| 87 | /** |
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| 88 | * An upgrade lock. Objects loaded in this lock mode are |
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| 89 | * materialized using an SQL <tt>select ... for update</tt>. |
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| 90 | */ |
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| 91 | public static final LockMode UPGRADE = new LockMode(10, "UPGRADE"); |
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| 92 | /** |
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| 93 | * Attempt to obtain an upgrade lock, using an Oracle-style |
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| 94 | * <tt>select for update nowait</tt>. The semantics of |
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| 95 | * this lock mode, once obtained, are the same as |
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| 96 | * <tt>UPGRADE</tt>. |
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| 97 | */ |
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| 98 | public static final LockMode UPGRADE_NOWAIT = new LockMode(10, "UPGRADE_NOWAIT"); |
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| 99 | /** |
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| 100 | * A <tt>WRITE</tt> lock is obtained when an object is updated |
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| 101 | * or inserted. This lock mode is for internal use only and is |
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| 102 | * not a valid mode for <tt>load()</tt> or <tt>lock()</tt> (both |
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| 103 | * of which throw exceptions if WRITE is specified). |
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| 104 | */ |
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| 105 | public static final LockMode WRITE = new LockMode(10, "WRITE"); |
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| 106 | |||
| 107 | /** |
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| 108 | * Similiar to {@link #UPGRADE} except that, for versioned entities, |
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| 109 | * it results in a forced version increment. |
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| 110 | */ |
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| 111 | public static final LockMode FORCE = new LockMode( 15, "FORCE" ); |
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| 112 | |||
| 113 | static { |
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| 114 | INSTANCES.put( NONE.name, NONE ); |
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| 115 | INSTANCES.put( READ.name, READ ); |
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| 116 | INSTANCES.put( UPGRADE.name, UPGRADE ); |
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| 117 | INSTANCES.put( UPGRADE_NOWAIT.name, UPGRADE_NOWAIT ); |
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| 118 | INSTANCES.put( WRITE.name, WRITE ); |
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| 119 | INSTANCES.put( FORCE.name, FORCE ); |
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| 120 | } |
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| 121 | |||
| 122 | private Object readResolve() { |
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| 123 | return parse( name ); |
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| 124 | } |
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| 125 | |||
| 126 | public static LockMode parse(String name) { |
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| 127 | return ( LockMode ) INSTANCES.get(name); |
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| 128 | } |
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| 129 | } |