MethodClassExtractor


1   /*
2    * The contents of this file are subject to the terms 
3    * of the Common Development and Distribution License 
4    * (the "License").  You may not use this file except 
5    * in compliance with the License.
6    * 
7    * You can obtain a copy of the license at 
8    * glassfish/bootstrap/legal/CDDLv1.0.txt or 
9    * https://glassfish.dev.java.net/public/CDDLv1.0.html. 
10   * See the License for the specific language governing 
11   * permissions and limitations under the License.
12   * 
13   * When distributing Covered Code, include this CDDL 
14   * HEADER in each file and include the License file at 
15   * glassfish/bootstrap/legal/CDDLv1.0.txt.  If applicable, 
16   * add the following below this CDDL HEADER, with the 
17   * fields enclosed by brackets "[]" replaced with your 
18   * own identifying information: Portions Copyright [yyyy] 
19   * [name of copyright owner]
20   */
21  // Copyright (c) 1998, 2006, Oracle. All rights reserved.  
22  package oracle.toplink.essentials.descriptors;
23  
24  import java.lang.reflect.*;
25  import java.security.AccessController  ;
26  import java.security.PrivilegedActionException  ;
27  
28  import oracle.toplink.essentials.internal.helper.*;
29  import oracle.toplink.essentials.exceptions.*;
30  import oracle.toplink.essentials.descriptors.ClassDescriptor;
31  import oracle.toplink.essentials.internal.sessions.AbstractRecord;
32  import oracle.toplink.essentials.sessions.Session;
33  import oracle.toplink.essentials.sessions.Record;
34  import oracle.toplink.essentials.internal.security.*;
35  
36  /**
37   * <p><b>Purpose</b>:
38   * Used to allow complex inheritance support.  Typically class indicators are used to define inheritance in the database,
39   * however in complex cases the class type may be determined through another mechanism.
40   * The method calls a static method on the descriptor class to determine the class to use for the database row.
41   *
42   * @see oracle.toplink.essentials.descriptors.InheritancePolicy#setClassExtractor(ClassExtrator)
43   */
44  public class MethodClassExtractor extends ClassExtractor {
45      protected transient ClassDescriptor descriptor;
46      protected String   classExtractionMethodName;
47      protected transient Method classExtractionMethod;
48  
49      /**
50       * INTERNAL:
51       * Return all the classExtractionMethod
52       */
53      public Method getClassExtractionMethod() {
54          return classExtractionMethod;
55      }
56  
57      /**
58       * PUBLIC:
59       * A class extraction method can be registered with the descriptor to override the default inheritance mechanism.
60       * This allows for the class indicator field to not be used, and a user defined one instead.
61       * The method registered must be a static method on the class that the descriptor is for,
62       * the method must take DatabaseRow as argument, and must return the class to use for that row.
63       * This method will be used to decide which class to instantiate when reading from the database.
64       * It is the application's responsiblity to populate any typing information in the database required
65       * to determine the class from the row.
66       * If this method is used then the class indicator field and mapping cannot be used,
67       * also the descriptor's withAllSubclasses and onlyInstances expressions must also be setup correctly.
68       */
69      public String   getClassExtractionMethodName() {
70          return classExtractionMethodName;
71      }
72  
73      /**
74       * INTERNAL:
75       */
76      protected void setClassExtractionMethod(Method classExtractionMethod) {
77          this.classExtractionMethod = classExtractionMethod;
78      }
79  
80      /**
81       * PUBLIC:
82       * A class extraction method can be registered with the descriptor to override the default inheritance mechanism.
83       * This allows for the class indicator field to not be used, and a user defined one instead.
84       * The method registered must be a static method on the class that the descriptor is for,
85       * the method must take DatabaseRow as argument, and must return the class to use for that row.
86       * This method will be used to decide which class to instantiate when reading from the database.
87       * It is the application's responsiblity to populate any typing information in the database required
88       * to determine the class from the row.
89       * If this method is used then the class indicator field and mapping cannot be used,
90       * also the descriptor's withAllSubclasses and onlyInstances expressions must also be setup correctly.
91       */
92      public void setClassExtractionMethodName(String   staticClassClassExtractionMethod) {
93          this.classExtractionMethodName = staticClassClassExtractionMethod;
94      }
95  
96      /**
97       * INTERNAL:
98       * Setup the default classExtractionMethod, or if one was specified by the user make sure it is valid.
99       */
100     public void initialize(ClassDescriptor descriptor, Session session) throws DescriptorException {
101         setDescriptor(descriptor);
102         Class  [] declarationParameters = new Class  [1];
103         declarationParameters[0] = ClassConstants.DatabaseRow_Class;
104 
105         try {
106             setClassExtractionMethod(Helper.getDeclaredMethod(descriptor.getJavaClass(), getClassExtractionMethodName(), declarationParameters));
107         } catch (NoSuchMethodException   ignore) {
108             declarationParameters[0] = ClassConstants.Record_Class;
109             try {
110                 setClassExtractionMethod(Helper.getDeclaredMethod(descriptor.getJavaClass(), getClassExtractionMethodName(), declarationParameters));
111             } catch (NoSuchMethodException   exception) {
112                 throw DescriptorException.noSuchMethodWhileInitializingClassExtractionMethod(getClassExtractionMethodName(), descriptor, exception);
113             }
114         } catch (SecurityException   exception) {
115             throw DescriptorException.securityWhileInitializingClassExtractionMethod(getClassExtractionMethodName(), descriptor, exception);
116         }
117 
118         // CR#2818667 Ensure the method is static.
119         if (!Modifier.isStatic(getClassExtractionMethod().getModifiers())) {
120             throw DescriptorException.classExtractionMethodMustBeStatic(getClassExtractionMethodName(), descriptor);
121         }
122     }
123 
124     /**
125      * INTERNAL
126      * Extract/compute the class from the database row and return the class.
127      * Map is used as the public interface to database row, the key is the field name,
128      * the value is the database value.
129      */
130     public Class   extractClassFromRow(Record row, oracle.toplink.essentials.sessions.Session session) {
131         Class   classForRow;
132 
133         try {
134             Object  [] arguments = new Object  [1];
135             arguments[0] = row;
136             if (PrivilegedAccessHelper.shouldUsePrivilegedAccess()){
137                 try {
138                     classForRow = (Class  )AccessController.doPrivileged(new PrivilegedMethodInvoker(getClassExtractionMethod(), null, arguments));
139                 } catch (PrivilegedActionException   exception) {
140                     Exception   throwableException = exception.getException();
141                     if (throwableException instanceof IllegalAccessException  ) {
142                         throw DescriptorException.illegalAccessWhileInvokingRowExtractionMethod((AbstractRecord)row, getClassExtractionMethod(), getDescriptor(), throwableException);
143                     } else {
144                         throw DescriptorException.targetInvocationWhileInvokingRowExtractionMethod((AbstractRecord)row, getClassExtractionMethod(), getDescriptor(), throwableException);
145                     }
146                 }
147             } else {
148                 classForRow = (Class  )PrivilegedAccessHelper.invokeMethod(getClassExtractionMethod(), null, arguments);
149             }
150         } catch (IllegalAccessException   exception) {
151             throw DescriptorException.illegalAccessWhileInvokingRowExtractionMethod((AbstractRecord)row, getClassExtractionMethod(), getDescriptor(), exception);
152         } catch (InvocationTargetException exception) {
153             throw DescriptorException.targetInvocationWhileInvokingRowExtractionMethod((AbstractRecord)row, getClassExtractionMethod(), getDescriptor(), exception);
154         }
155 
156         return classForRow;
157     }
158 
159     /**
160      * INTERNAL:
161      * Return the descriptor.
162      */
163     protected ClassDescriptor getDescriptor() {
164         return descriptor;
165     }
166 
167     /**
168      * INTERNAL:
169      * Set the descriptor.
170      */
171     protected void setDescriptor(ClassDescriptor descriptor) {
172         this.descriptor = descriptor;
173     }
174 }
175
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags