IdentifierValue


1   //$Id: IdentifierValue.java,v 1.1 2005/06/05 04:31:33 oneovthafew Exp $
2   package org.hibernate.engine;
3   
4   import java.io.Serializable  ;
5   
6   import org.apache.commons.logging.Log;
7   import org.apache.commons.logging.LogFactory;
8   
9   /**
10   * A strategy for determining if an identifier value is an identifier of
11   * a new transient instance or a previously persistent transient instance.
12   * The strategy is determined by the <tt>unsaved-value</tt> attribute in
13   * the mapping file.
14   * 
15   * @author Gavin King
16   */
17  public class IdentifierValue {
18  
19      private static final Log log = LogFactory.getLog(IdentifierValue.class);
20      
21      private final Serializable   value;
22      
23      /**
24       * Always assume the transient instance is newly instantiated
25       */
26      public static final IdentifierValue ANY = new IdentifierValue() {
27          public final Boolean   isUnsaved(Serializable   id) {
28              log.trace("id unsaved-value strategy ANY");
29              return Boolean.TRUE;
30          }
31          public Serializable   getDefaultValue(Serializable   currentValue) {
32              return currentValue;
33          }
34          public String   toString() {
35              return "SAVE_ANY";
36          }
37      };
38      
39      /**
40       * Never assume the transient instance is newly instantiated
41       */
42      public static final IdentifierValue NONE = new IdentifierValue() {
43          public final Boolean   isUnsaved(Serializable   id) {
44              log.trace("id unsaved-value strategy NONE");
45              return Boolean.FALSE;
46          }
47          public Serializable   getDefaultValue(Serializable   currentValue) {
48              return currentValue;
49          }
50          public String   toString() {
51              return "SAVE_NONE";
52          }
53      };
54      
55      /**
56       * Assume the transient instance is newly instantiated if the identifier
57       * is null.
58       */
59      public static final IdentifierValue NULL = new IdentifierValue() {
60          public final Boolean   isUnsaved(Serializable   id) {
61              log.trace("id unsaved-value strategy NULL");
62              return id==null ? Boolean.TRUE : Boolean.FALSE;
63          }
64          public Serializable   getDefaultValue(Serializable   currentValue) {
65              return null;
66          }
67          public String   toString() {
68              return "SAVE_NULL";
69          }
70      };
71      
72      /**
73       * Assume nothing.
74       */
75      public static final IdentifierValue UNDEFINED = new IdentifierValue() {
76          public final Boolean   isUnsaved(Serializable   id) {
77              log.trace("id unsaved-value strategy UNDEFINED");
78              return null;
79          }
80          public Serializable   getDefaultValue(Serializable   currentValue) {
81              return null;
82          }
83          public String   toString() {
84              return "UNDEFINED";
85          }
86      };
87      
88      protected IdentifierValue() {
89          this.value = null;
90      }
91      
92      /**
93       * Assume the transient instance is newly instantiated if
94       * its identifier is null or equal to <tt>value</tt>
95       */
96      public IdentifierValue(Serializable   value) {
97          this.value = value;
98      }
99      
100     /**
101      * Does the given identifier belong to a new instance?
102      */
103     public Boolean   isUnsaved(Serializable   id) {
104         if ( log.isTraceEnabled() ) log.trace("id unsaved-value: " + value);
105         return id==null || id.equals(value) ? Boolean.TRUE : Boolean.FALSE;
106     }
107     
108     public Serializable   getDefaultValue(Serializable   currentValue) {
109         return value;
110     }
111     
112     public String   toString() {
113         return "identifier unsaved-value: " + value;
114     }
115 }
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