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Java > Open Source Codes > org > apache > commons > beanutils > ResultSetDynaClass


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17
18 package org.apache.commons.beanutils;
19
20
21 import java.sql.ResultSet JavaDoc;
22 import java.sql.SQLException JavaDoc;
23 import java.util.HashMap JavaDoc;
24 import java.util.Iterator JavaDoc;
25
26
27 /**
28  * <p>Implementation of <code>DynaClass</code> for DynaBeans that wrap the
29  * <code>java.sql.Row</code> objects of a <code>java.sql.ResultSet</code>.
30  * The normal usage pattern is something like:</p>
31  * <pre>
32  * ResultSet rs = ...;
33  * ResultSetDynaClass rsdc = new ResultSetDynaClass(rs);
34  * Iterator rows = rsdc.iterator();
35  * while (rows.hasNext()) {
36  * DynaBean row = (DynaBean) rows.next();
37  * ... process this row ...
38  * }
39  * rs.close();
40  * </pre>
41  *
42  * <p>Each column in the result set will be represented as a DynaBean
43  * property of the corresponding name (optionally forced to lower case
44  * for portability).</p>
45  *
46  * <p><strong>WARNING</strong> - Any {@link DynaBean} instance returned by
47  * this class, or from the <code>Iterator</code> returned by the
48  * <code>iterator()</code> method, is directly linked to the row that the
49  * underlying result set is currently positioned at. This has the following
50  * implications:</p>
51  * <ul>
52  * <li>Once you retrieve a different {@link DynaBean} instance, you should
53  * no longer use any previous instance.</li>
54  * <li>Changing the position of the underlying result set will change the
55  * data that the {@link DynaBean} references.</li>
56  * <li>Once the underlying result set is closed, the {@link DynaBean}
57  * instance may no longer be used.</li>
58  * </ul>
59  *
60  * <p>Any database data that you wish to utilize outside the context of the
61  * current row of an open result set must be copied. For example, you could
62  * use the following code to create standalone copies of the information in
63  * a result set:</p>
64  * <pre>
65  * ArrayList results = new ArrayList(); // To hold copied list
66  * ResultSetDynaClass rsdc = ...;
67  * DynaProperty properties[] = rsdc.getDynaProperties();
68  * BasicDynaClass bdc =
69  * new BasicDynaClass("foo", BasicDynaBean.class,
70  * rsdc.getDynaProperties());
71  * Iterator rows = rsdc.iterator();
72  * while (rows.hasNext()) {
73  * DynaBean oldRow = (DynaBean) rows.next();
74  * DynaBean newRow = bdc.newInstance();
75  * PropertyUtils.copyProperties(newRow, oldRow);
76  * results.add(newRow);
77  * }
78  * </pre>
79  *
80  * @author Craig R. McClanahan
81  * @version $Revision: 1.15 $ $Date: 2004/02/28 13:18:33 $
82  */
83
84 public class ResultSetDynaClass extends JDBCDynaClass implements DynaClass {
85
86
87     // ----------------------------------------------------------- Constructors
88
89
90     /**
91      * <p>Construct a new ResultSetDynaClass for the specified
92      * <code>ResultSet</code>. The property names corresponding
93      * to column names in the result set will be lower cased.</p>
94      *
95      * @param resultSet The result set to be wrapped
96      *
97      * @exception NullPointerException if <code>resultSet</code>
98      * is <code>null</code>
99      * @exception SQLException if the metadata for this result set
100      * cannot be introspected
101      */
102     public ResultSetDynaClass(ResultSet JavaDoc resultSet) throws SQLException JavaDoc {
103
104         this(resultSet, true);
105
106     }
107
108
109     /**
110      * <p>Construct a new ResultSetDynaClass for the specified
111      * <code>ResultSet</code>. The property names corresponding
112      * to the column names in the result set will be lower cased or not,
113      * depending on the specified <code>lowerCase</code> value.</p>
114      *
115      * <p><strong>WARNING</strong> - If you specify <code>false</code>
116      * for <code>lowerCase</code>, the returned property names will
117      * exactly match the column names returned by your JDBC driver.
118      * Because different drivers might return column names in different
119      * cases, the property names seen by your application will vary
120      * depending on which JDBC driver you are using.</p>
121      *
122      * @param resultSet The result set to be wrapped
123      * @param lowerCase Should property names be lower cased?
124      *
125      * @exception NullPointerException if <code>resultSet</code>
126      * is <code>null</code>
127      * @exception SQLException if the metadata for this result set
128      * cannot be introspected
129      */
130     public ResultSetDynaClass(ResultSet JavaDoc resultSet, boolean lowerCase)
131         throws SQLException JavaDoc {
132
133         if (resultSet == null) {
134             throw new NullPointerException JavaDoc();
135         }
136         this.resultSet = resultSet;
137         this.lowerCase = lowerCase;
138         introspect(resultSet);
139
140     }
141
142
143     // ----------------------------------------------------- Instance Variables
144
145
146     /**
147      * <p>The <code>ResultSet</code> we are wrapping.</p>
148      */
149     protected ResultSet JavaDoc resultSet = null;
150
151
152     // --------------------------------------------------------- Public Methods
153
154
155     /**
156      * <p>Return an <code>Iterator</code> of {@link DynaBean} instances for
157      * each row of the wrapped <code>ResultSet</code>, in "forward" order.
158      * Unless the underlying result set supports scrolling, this method
159      * should be called only once.</p>
160      */
161     public Iterator JavaDoc iterator() {
162
163         return (new ResultSetIterator(this));
164
165     }
166
167
168     // -------------------------------------------------------- Package Methods
169
170
171     /**
172      * <p>Return the result set we are wrapping.</p>
173      */
174     ResultSet JavaDoc getResultSet() {
175
176         return (this.resultSet);
177
178     }
179
180
181     // ------------------------------------------------------ Protected Methods
182
183     /**
184      * <p>Loads the class of the given name which by default uses the class loader used
185      * to load this library.
186      * Dervations of this class could implement alternative class loading policies such as
187      * using custom ClassLoader or using the Threads's context class loader etc.
188      * </p>
189      */
190     protected Class JavaDoc loadClass(String JavaDoc className) throws SQLException JavaDoc {
191
192         try {
193             return getClass().getClassLoader().loadClass(className);
194         }
195         catch (Exception JavaDoc e) {
196             throw new SQLException JavaDoc("Cannot load column class '" +
197                                    className + "': " + e);
198         }
199     }
200 }
201
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