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Java > Open Source Codes > org > apache > torque > adapter > DBDB2App


1 package org.apache.torque.adapter;
2
3 /*
4  * Licensed to the Apache Software Foundation (ASF) under one
5  * or more contributor license agreements. See the NOTICE file
6  * distributed with this work for additional information
7  * regarding copyright ownership. The ASF licenses this file
8  * to you under the Apache License, Version 2.0 (the
9  * "License"); you may not use this file except in compliance
10  * with the License. You may obtain a copy of the License at
11  *
12  * http://www.apache.org/licenses/LICENSE-2.0
13  *
14  * Unless required by applicable law or agreed to in writing,
15  * software distributed under the License is distributed on an
16  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17  * KIND, either express or implied. See the License for the
18  * specific language governing permissions and limitations
19  * under the License.
20  */
21
22 import java.sql.Connection JavaDoc;
23 import java.sql.SQLException JavaDoc;
24
25 import org.apache.torque.util.Query;
26
27 /**
28  * This is used to connect via the Application-Driver to DB2
29  * databases.
30  *
31  * <a HREF="http://www-306.ibm.com/software/data/db2/">http://www-306.ibm.com/software/data/db2/</a>
32  *
33  * @author <a HREF="mailto:hakan42@gmx.de">Hakan Tandogan</a>
34  * @author <a HREF="mailto:vido@ldh.org">Augustin Vidovic</a>
35  * @version $Id: DBDB2App.java 473821 2006-11-11 22:37:25Z tv $
36  */
37 public class DBDB2App extends AbstractDBAdapter
38 {
39     /**
40      * Serial version
41      */
42     private static final long serialVersionUID = -3097347241360840675L;
43
44     /**
45      * Empty constructor.
46      */
47     protected DBDB2App()
48     {
49     }
50
51     /**
52      * This method is used to ignore case.
53      *
54      * @param in The string to transform to upper case.
55      * @return The upper case string.
56      */
57     public String JavaDoc toUpperCase(String JavaDoc in)
58     {
59         String JavaDoc s = new StringBuffer JavaDoc("UPPER(").append(in).append(")").toString();
60         return s;
61     }
62
63     /**
64      * This method is used to ignore case.
65      *
66      * @param in The string whose case to ignore.
67      * @return The string in a case that can be ignored.
68      */
69     public String JavaDoc ignoreCase(String JavaDoc in)
70     {
71         String JavaDoc s = new StringBuffer JavaDoc("UPPER(").append(in).append(")").toString();
72         return s;
73     }
74
75     /**
76      * @see org.apache.torque.adapter.DB#getIDMethodType()
77      */
78     public String JavaDoc getIDMethodType()
79     {
80         return NO_ID_METHOD;
81     }
82
83     /**
84      * @see org.apache.torque.adapter.DB#getIDMethodSQL(Object obj)
85      */
86     public String JavaDoc getIDMethodSQL(Object JavaDoc obj)
87     {
88         return null;
89     }
90
91     /**
92      * Locks the specified table.
93      *
94      * @param con The JDBC connection to use.
95      * @param table The name of the table to lock.
96      * @exception SQLException No Statement could be created or executed.
97      */
98     public void lockTable(Connection JavaDoc con, String JavaDoc table) throws SQLException JavaDoc
99     {
100     }
101
102     /**
103      * Unlocks the specified table.
104      *
105      * @param con The JDBC connection to use.
106      * @param table The name of the table to unlock.
107      * @exception SQLException No Statement could be created or executed.
108      */
109     public void unlockTable(Connection JavaDoc con, String JavaDoc table) throws SQLException JavaDoc
110     {
111     }
112
113     /**
114      * This method is used to check whether the database supports
115      * limiting the size of the resultset.
116      *
117      * @return LIMIT_STYLE_DB2.
118      * @deprecated This should not be exposed to the outside
119      */
120     public int getLimitStyle()
121     {
122         return DB.LIMIT_STYLE_DB2;
123     }
124
125     /**
126      * Return true for DB2
127      * @see org.apache.torque.adapter.AbstractDBAdapter#supportsNativeLimit()
128      */
129     public boolean supportsNativeLimit()
130     {
131         return true;
132     }
133
134     /**
135      * Return true for DB2
136      * @see org.apache.torque.adapter.AbstractDBAdapter#supportsNativeOffset()
137      */
138     public boolean supportsNativeOffset()
139     {
140         return true;
141     }
142
143     /**
144      * Build DB2 (OLAP) -style query with limit or offset.
145      * If the original SQL is in variable: query then the requlting
146      * SQL looks like this:
147      * <pre>
148      * SELECT B.* FROM (
149      * SELECT A.*, row_number() over() as TORQUE$ROWNUM FROM (
150      * query
151      * ) A
152      * ) B WHERE B.TORQUE$ROWNUM > offset AND B.TORQUE$ROWNUM
153      * <= offset + limit
154      * </pre>
155      *
156      * @param query The query to modify
157      * @param offset the offset Value
158      * @param limit the limit Value
159      */
160     public void generateLimits(Query query, int offset, int limit)
161     {
162         StringBuffer JavaDoc preLimit = new StringBuffer JavaDoc()
163         .append("SELECT B.* FROM ( ")
164         .append("SELECT A.*, row_number() over() AS TORQUE$ROWNUM FROM ( ");
165
166         StringBuffer JavaDoc postLimit = new StringBuffer JavaDoc()
167                 .append(" ) A ")
168                 .append(" ) B WHERE ");
169
170         if (offset > 0)
171         {
172             postLimit.append(" B.TORQUE$ROWNUM > ")
173                     .append(offset);
174
175             if (limit >= 0)
176             {
177                 postLimit.append(" AND B.TORQUE$ROWNUM <= ")
178                         .append(offset + limit);
179             }
180         }
181         else
182         {
183             postLimit.append(" B.TORQUE$ROWNUM <= ")
184                     .append(limit);
185         }
186
187         query.setPreLimit(preLimit.toString());
188         query.setPostLimit(postLimit.toString());
189         query.setLimit(null);
190     }
191 }
192
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