Query


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.List  ;
19  
20  /**
21   * represents Queries that can be used by the OJB PersistenceBroker
22   * to retrieve Objects from the underlying DB.
23   * Until now there are two implementations:
24   * 1. QueryByCriteria, represents SELECT * FROM ... WHERE ... queries
25   * 2. QueryByIdentity, uses Example objects or OIDs
26   * as templates for the db lookup
27   * there could additional implementations, e.g for user defined SQL
28   *
29   * For the Criteria API I reused code from the COBRA project,
30   * as you will see by their class comments.
31   *
32   * I removed all stuff that relies on knowlegde of the DataDictionary
33   * or MetaData layer. The Query and Criteria classes thus don't know
34   * how to build SQL statements, as in the COBRA original sources.
35   * I use the this classes as mere data-structures, that are
36   * processed by the OJB Accesslayer (SqlGenerator, JdbcAccess).
37   *
38   * This design will allow to reuse the org.apache.ojb.broker.query package in other
39   * projects without breaking any references. I hope this will be
40   * useful for someone.
41   *
42   * @author Thomas Mahler
43   * @version $Id: Query.java,v 1.17.2.3 2005/12/21 22:27:09 tomdz Exp $
44   */
45  public interface Query extends java.io.Serializable  
46  {
47      static final long serialVersionUID = 7616997212439931319L;
48      
49      public static final int NO_START_AT_INDEX = 0;
50      public static final int NO_END_AT_INDEX = 0;
51      public static final boolean SCROLLABLE = true;
52      public static final boolean NOT_SCROLLABLE = false;
53  
54      /**
55       * return the criteria of the query if present or null.
56       */
57      public abstract Criteria getCriteria();
58  
59      /**
60       * return the criteria of the query if present or null.
61       */
62      public abstract Criteria getHavingCriteria();
63  
64      /**
65       * return the template Object if present or null
66       */
67      public abstract Object   getExampleObject();
68  
69      /**
70       * return the target class, representing the extend to be searched
71       */
72      public abstract Class   getSearchClass();
73  
74      /**
75       * return the base class, with respect to which all paths are done
76       */
77      public abstract Class   getBaseClass();
78  
79      /**
80       *  return true if select DISTINCT should be used
81       */
82      public boolean isDistinct();
83  
84      /**
85       * Answer the orderBy of all Criteria and Sub Criteria the elements are of
86       * class FieldHelper
87       * @return List of FieldHelper
88       */
89      public List   getOrderBy();
90  
91      /**
92       * Gets the groupby for ReportQueries of all Criteria and Sub Criteria
93       * the elements are of class FieldHelper
94       * @return List of FieldHelper
95       */
96      public List   getGroupBy();
97  
98      /**
99       *
100      * @return the row at which the query should start retrieving results. 
101      * If the start at index is 0, then ignore all cursor control.
102      */
103     int getStartAtIndex();
104 
105     /**
106      * Set the row at which the query should start retrieving results, inclusive
107      * first row is 1
108      * @param startAtIndex starting index, inclusive.
109      */
110     void setStartAtIndex(int startAtIndex);
111 
112     /**
113      *
114      * @return the row at which the query should stop retrieving results. 
115      * If the end at index is 0, ignore all cursor control
116      */
117     int getEndAtIndex();
118 
119     /**
120      * Set the row at which the query should stop retrieving results, inclusive.
121      * first row is 1
122      * @param endAtIndex ending index, inclusive
123      */
124     void setEndAtIndex(int endAtIndex);
125 
126     /**
127      * Returns the names of Relationships to be prefetched
128      * @return List of Strings
129      */
130     public List   getPrefetchedRelationships();
131 
132     /**
133      * @deprecated 
134      * @param size
135      */
136     void fullSize(int size);
137     /**
138      * @deprecated use OJBIterator.fullSize()
139      * @return
140      */
141     int fullSize();
142 
143     void setWithExtents(boolean withExtents);
144     boolean getWithExtents();
145     
146     /**
147      * Answer true if start- and endIndex is set
148      * @return
149      */
150     public boolean usePaging();
151 
152     /**
153      * Set fetchSize hint for this Query. Passed to the JDBC driver on the
154      * Statement level. It is JDBC driver-dependant if this function has
155      * any effect at all, since fetchSize is only a hint.
156      * @param fetchSize the fetch size specific to this query
157      */
158     void setFetchSize(int fetchSize);
159 
160     /**
161      * Returns the fetchSize hint for this Query
162      * @return the fetch size hint specific to this query
163      * (or 0 if not set / using driver default)
164      */
165     int getFetchSize();
166 
167 }
168
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