BackrefPropertyAccessor


1   //$Id: BackrefPropertyAccessor.java,v 1.9 2005/07/16 22:20:47 oneovthafew Exp $
2   package org.hibernate.property;
3   
4   import java.lang.reflect.Method  ;
5   import java.util.Map  ;
6   import java.io.Serializable  ;
7   
8   import org.hibernate.HibernateException;
9   import org.hibernate.engine.SessionImplementor;
10  import org.hibernate.engine.SessionFactoryImplementor;
11  
12  /**
13   * Represents a "back-reference" to the id of a collection owner.
14   *
15   * @author Gavin King
16   */
17  public class BackrefPropertyAccessor implements PropertyAccessor {
18  
19      private final String   propertyName;
20      private final String   entityName;
21  
22      /**
23       * A placeholder for a property value, indicating that
24       * we don't know the value of the back reference
25       */
26      public static final Serializable   UNKNOWN = new Serializable  () {
27          public String   toString() { return "<unknown>"; }
28          public Object   readResolve() {
29              return UNKNOWN;
30          }
31      };
32      
33      /**
34       * Constructs a new instance of BackrefPropertyAccessor.
35       *
36       * @param collectionRole The collection role which this back ref references.
37       */
38      public BackrefPropertyAccessor(String   collectionRole, String   entityName) {
39          this.propertyName = collectionRole.substring( entityName.length() + 1 );
40          this.entityName = entityName;
41      }
42  
43      public Setter getSetter(Class   theClass, String   propertyName) {
44          return new BackrefSetter();
45      }
46  
47      public Getter getGetter(Class   theClass, String   propertyName) {
48          return new BackrefGetter();
49      }
50  
51  
52      /**
53       * The Setter implementation for id backrefs.
54       */
55      public static final class BackrefSetter implements Setter {
56  
57          public Method   getMethod() {
58              return null;
59          }
60  
61          public String   getMethodName() {
62              return null;
63          }
64  
65          public void set(Object   target, Object   value, SessionFactoryImplementor factory) {
66              // this page intentionally left blank :)
67          }
68  
69      }
70  
71  
72      /**
73       * The Getter implementation for id backrefs.
74       */
75      public class BackrefGetter implements Getter {
76          
77          public Object   getForInsert(Object   target, Map   mergeMap, SessionImplementor session)
78          throws HibernateException {
79              if (session==null) {
80                  return UNKNOWN;
81              }
82              else {
83                  return session.getPersistenceContext()
84                          .getOwnerId( entityName, propertyName, target, mergeMap );
85              }
86          }
87  
88          public Object   get(Object   target)  {
89              return UNKNOWN;
90          }
91  
92          public Method   getMethod() {
93              return null;
94          }
95  
96          public String   getMethodName() {
97              return null;
98          }
99  
100         public Class   getReturnType() {
101             return Object  .class;
102         }
103     }
104 }
105 
106
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