QueryFactory


1   package org.apache.ojb.broker.query;
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  import java.util.Collection  ;
19  import java.util.HashSet  ;
20  import java.util.Vector  ;
21  
22  import org.apache.ojb.broker.metadata.ClassDescriptor;
23  import org.apache.ojb.broker.metadata.DescriptorRepository;
24  import org.apache.ojb.broker.metadata.FieldDescriptor;
25  import org.apache.ojb.broker.metadata.MetadataManager;
26  
27  /**
28   * Insert the type's description here.
29   * @author <a HREF="mailto:thma@apache.org">Thomas Mahler<a>
30   * @version $Id: QueryFactory.java,v 1.17.2.1 2005/12/21 22:27:09 tomdz Exp $
31   */
32  public final class QueryFactory
33  {
34      private static DescriptorRepository getRepository()
35      {
36          return MetadataManager.getInstance().getRepository();
37      }
38  
39      /**
40       * create a new ReportQueryByCriteria
41       * @param classToSearchFrom
42       * @param criteria
43       * @param distinct
44       * @return ReportQueryByCriteria
45       */
46      public static ReportQueryByCriteria newReportQuery(Class   classToSearchFrom, String  [] columns, Criteria criteria, boolean distinct)
47      {
48          criteria = addCriteriaForOjbConcreteClasses(getRepository().getDescriptorFor(classToSearchFrom), criteria);
49          return new ReportQueryByCriteria(classToSearchFrom, columns, criteria, distinct);
50      }
51  
52      /**
53       * create a new ReportQueryByCriteria
54       * @param classToSearchFrom
55       * @param criteria
56       * @param distinct
57       * @return ReportQueryByCriteria
58       */
59      public static ReportQueryByCriteria newReportQuery(Class   classToSearchFrom, Criteria criteria, boolean distinct)
60      {
61          criteria = addCriteriaForOjbConcreteClasses(getRepository().getDescriptorFor(classToSearchFrom), criteria);
62          return newReportQuery(classToSearchFrom, null, criteria, distinct);
63      }
64  
65      /**
66       * create a new ReportQueryByCriteria
67       * @param classToSearchFrom
68       * @param criteria
69       * @return ReportQueryByCriteria
70       */
71      public static ReportQueryByCriteria newReportQuery(Class   classToSearchFrom, Criteria criteria)
72      {
73          return newReportQuery(classToSearchFrom, criteria, false);
74      }
75  
76      /**
77       * Method declaration
78       * @param classToSearchFrom
79       * @param criteria
80       * @param distinct
81       * @return QueryByCriteria
82       */
83      public static QueryByCriteria newQuery(Class   classToSearchFrom, Criteria criteria, boolean distinct)
84      {
85          criteria = addCriteriaForOjbConcreteClasses(getRepository().getDescriptorFor(classToSearchFrom), criteria);
86          return new QueryByCriteria(classToSearchFrom, criteria, distinct);
87      }
88  
89      /**
90       * Method declaration
91       * @param classToSearchFrom
92       * @param criteria
93       * @return QueryByCriteria
94       */
95      public static QueryByCriteria newQuery(Class   classToSearchFrom, Criteria criteria)
96      {
97          return newQuery(classToSearchFrom, criteria, false);
98      }
99  
100     /**
101      * Return a QueryByIdentity for example_or_identity
102      * @param example_or_identity
103      * @return QueryByIdentity
104      */
105     public static QueryByIdentity newQuery(Object   example_or_identity)
106     {
107         return newQueryByIdentity(example_or_identity);
108     }
109 
110     /**
111      * Return a QueryByIdentity for example_or_identity
112      * @param example_or_identity
113      * @return QueryByIdentity
114      */
115     public static QueryByIdentity newQueryByIdentity(Object   example_or_identity)
116     {
117         return new QueryByIdentity(example_or_identity);
118     }
119 
120     /**
121      * Return a QueryByCriteria for example
122      * <br>Use with care because building of Query is not foolproof !!!
123      * @param example
124      * @return QueryByCriteria
125      */
126     public static QueryByCriteria newQueryByExample(Object   example)
127     {
128         return new QueryByCriteria(example);
129     }
130 
131     /**
132      * @param classToSearchFrom
133      * @param indirectionTable
134      * @param criteria
135      * @param distinct
136      * @return QueryByMtoNCriteria
137      */
138     public static QueryByMtoNCriteria newQuery(Class   classToSearchFrom, String   indirectionTable, Criteria criteria, boolean distinct)
139     {
140         criteria = addCriteriaForOjbConcreteClasses(getRepository().getDescriptorFor(classToSearchFrom), criteria);
141         return new QueryByMtoNCriteria(classToSearchFrom, indirectionTable, criteria, distinct);
142     }
143 
144     /**
145      * @param classToSearchFrom
146      * @param indirectionTable
147      * @param criteria
148      * @return QueryByCriteria
149      */
150     public static QueryByCriteria newQuery(Class   classToSearchFrom, String   indirectionTable, Criteria criteria)
151     {
152         criteria = addCriteriaForOjbConcreteClasses(getRepository().getDescriptorFor(classToSearchFrom), criteria);
153         return new QueryByMtoNCriteria(classToSearchFrom, indirectionTable, criteria);
154     }
155 
156     /**
157      * Factory method for QueryBySQL
158      * @param classToSearchFrom
159      * @param anSqlStatement
160      * @return QueryBySQL
161      */
162     public static QueryBySQL newQuery(Class   classToSearchFrom, String   anSqlStatement)
163     {
164         return new QueryBySQL(classToSearchFrom, anSqlStatement);
165     }
166 
167     /**
168      * Searches the class descriptor for the ojbConcrete class attribute
169      * if it finds the concrete class attribute, append a where clause which
170      * specifies we can load all classes that are this type or extents of this type.
171      * @param cld
172      * @return the extent classes
173      */
174     private static Collection   getExtentClasses(ClassDescriptor cld)
175     {
176         /**
177          * 1. check if this class has a ojbConcreteClass attribute
178          */
179         FieldDescriptor fd = cld.getFieldDescriptorByName(ClassDescriptor.OJB_CONCRETE_CLASS);
180         Collection   classes = new HashSet  ();  // use same class only once
181         if (fd != null)
182         {
183             classes.add(cld.getClassOfObject().getName());
184         }
185 
186         /**
187          * 2. if this class has extents/is an extent search for all extents
188          */
189         if (cld.isExtent())
190         {
191             Vector   extentClasses = cld.getExtentClasses();
192 
193             /**
194              * 3. get all extents for this class
195              */
196             for (int i = 0; i < extentClasses.size(); i++)
197             {
198                 Class   ec = (Class  ) extentClasses.get(i);
199                 ClassDescriptor extCld = cld.getRepository().getDescriptorFor(ec);
200                 classes.addAll(getExtentClasses(extCld));
201             }
202         }
203 
204         return classes;
205     }
206 
207     /**
208      * Searches the class descriptor for the ojbConcrete class attribute
209      * if it finds the concrete class attribute, append a where clause which
210      * specifies we can load all classes that are this type or extents of this type.
211      * @param cld
212      * @param crit
213      * @return the passed in Criteria object + optionally and'ed criteria with OR'd class
214      * type discriminators.
215      */
216     private static Criteria addCriteriaForOjbConcreteClasses(ClassDescriptor cld, Criteria crit)
217     {
218         /**
219          * 1. check if this class has a ojbConcreteClass attribute
220          */
221         Criteria concreteClassDiscriminator = null;
222         Collection   classes = getExtentClasses(cld);
223 
224         /**
225          * 1. create a new Criteria for objConcreteClass
226          */
227         if (!classes.isEmpty())
228         {
229             concreteClassDiscriminator = new Criteria();
230             if (classes.size() > 1)
231             {
232                 concreteClassDiscriminator = new Criteria();
233                 concreteClassDiscriminator.addIn(ClassDescriptor.OJB_CONCRETE_CLASS, classes);
234             }
235             else
236             {
237                 concreteClassDiscriminator.addEqualTo(ClassDescriptor.OJB_CONCRETE_CLASS, classes.toArray()[0]);
238             }
239         }
240 
241         /**
242          * 2. only add the AND (objConcreteClass = "some.class" OR....) if we've actually found concrete
243          * classes.
244          */
245         if (concreteClassDiscriminator != null)
246         {
247             /**
248              * it's possible there is no criteria attached to the query, and in this
249              * case we still have to add the IN/EqualTo criteria for the concrete class type
250              * so check if the crit is null and then create a blank one if needed.
251              */
252             if (crit == null)
253             {
254                 crit = new Criteria();
255             }
256  
257             crit.addAndCriteria(concreteClassDiscriminator);
258         }
259         /**
260          * will just return the passed in criteria if no OJB concrete class is attribute is found.
261          */
262         return crit;
263     }
264 
265 }
266
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