JDBCDynaClass


1   /*
2    * $Header: /cvsroot/valuelist/valuelist/src/java/net/mlw/vlh/adapter/jdbc/dynabean/fix/JDBCDynaClass.java,v 1.2 2005/08/19 16:06:29 smarek Exp $
3    * $Revision: 1.2 $
4    * $Date: 2005/08/19 16:06:29 $
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61  
62  package net.mlw.vlh.adapter.jdbc.dynabean.fix;
63  
64  import java.io.Serializable  ;
65  import java.sql.ResultSet  ;
66  import java.sql.ResultSetMetaData  ;
67  import java.sql.SQLException  ;
68  import java.util.ArrayList  ;
69  import java.util.HashMap  ;
70  import java.util.List  ;
71  import java.util.Map  ;
72  
73  import org.apache.commons.beanutils.DynaBean;
74  import org.apache.commons.beanutils.DynaClass;
75  import org.apache.commons.beanutils.DynaProperty;
76  
77  /**
78   * <p>Provides common logic for JDBC implementations of {@link DynaClass}.</p>
79   *
80   * @author   Craig R. McClanahan
81   * @author   George Franciscus
82   * @version $Revision: 1.2 $ $Date: 2005/08/19 16:06:29 $
83   */
84  
85  abstract class JDBCDynaClass implements DynaClass, Serializable   {
86  
87      // ----------------------------------------------------- Instance Variables
88  
89      /**
90       * <p>Flag defining whether column names should be lower cased when
91       * converted to property names.</p>
92       */
93      protected boolean lowerCase = true;
94  
95      /**
96       * <p>Flag defining whether column names should be the column name
97       * or the column label.</p>
98       */
99       protected boolean useName = true;
100          
101          
102     /**
103      * <p>The set of dynamic properties that are part of this
104      * {@link DynaClass}.</p>
105      */
106     protected DynaProperty properties[] = null;
107 
108     /**
109      * <p>The set of dynamic properties that are part of this
110      * {@link DynaClass}, keyed by the property name.  Individual descriptor
111      * instances will be the same instances as those in the
112      * <code>properties</code> list.</p>
113      */
114     protected Map   propertiesMap = new HashMap  ();
115 
116     // ------------------------------------------------------ DynaClass Methods
117 
118     /**
119      * <p>Return the name of this DynaClass (analogous to the
120      * <code>getName()</code> method of <code>java.lang.Class</code), which
121      * allows the same <code>DynaClass</code> implementation class to support
122      * different dynamic classes, with different sets of properties.</p>
123      */
124     public String   getName() {
125 
126         return (this.getClass().getName());
127 
128     }
129 
130     /**
131      * <p>Return a property descriptor for the specified property, if it
132      * exists; otherwise, return <code>null</code>.</p>
133      *
134      * @param name Name of the dynamic property for which a descriptor
135      *  is requested
136      *
137      * @exception IllegalArgumentException if no property name is specified
138      */
139     public DynaProperty getDynaProperty(String   name) {
140 
141         if (name == null) {
142             throw new IllegalArgumentException  ("No property name specified");
143         }
144         return ((DynaProperty) propertiesMap.get(name));
145 
146     }
147 
148     /**
149      * <p>Return an array of <code>ProperyDescriptors</code> for the properties
150      * currently defined in this DynaClass.  If no properties are defined, a
151      * zero-length array will be returned.</p>
152      */
153     public DynaProperty[] getDynaProperties() {
154 
155         return (properties);
156 
157     }
158 
159     /**
160      * <p>Instantiate and return a new DynaBean instance, associated
161      * with this DynaClass.  <strong>NOTE</strong> - This operation is not
162      * supported, and throws an exception.</p>
163      *
164      * @exception IllegalAccessException if the Class or the appropriate
165      *  constructor is not accessible
166      * @exception InstantiationException if this Class represents an abstract
167      *  class, an array class, a primitive type, or void; or if instantiation
168      *  fails for some other reason
169      */
170     public DynaBean newInstance()
171             throws IllegalAccessException  , InstantiationException   {
172 
173         throw new UnsupportedOperationException  ("newInstance() not supported");
174 
175     }
176 
177     /**
178      * <p>Loads and returns the <code>Class</code> of the given name.
179      * By default, a load from the thread context class loader is attempted.
180      * If there is no such class loader, the class loader used to load this
181      * class will be utilized.</p>
182      *
183      * @exception SQLException if an exception was thrown trying to load
184      *  the specified class
185      */
186     protected Class   loadClass(String   className) throws SQLException   {
187 
188         try {
189             ClassLoader   cl = Thread.currentThread().getContextClassLoader();
190             if (cl == null) {
191                     cl = this.getClass().getClassLoader();
192             }
193             return (cl.loadClass(className));
194         } catch (Exception   e) {
195             throw new SQLException  (
196                     "Cannot load column class '" + className + "': " + e);
197         }
198 
199     }
200 
201     /**
202      * <p>Factory method to create a new DynaProperty for the given index
203      * into the result set metadata.</p>
204      * 
205      * @param metadata is the result set metadata
206      * @param i is the column index in the metadata
207      * @return the newly created DynaProperty instance
208      */
209     protected DynaProperty createDynaProperty(
210                                     ResultSetMetaData   metadata,
211                                     int i)
212                                     throws SQLException   {
213 
214         String   name = ( useName ) ? metadata.getColumnName(i) : metadata.getColumnLabel(i);
215                           
216         if (lowerCase) {
217                name = name.toLowerCase();
218         }
219 
220         String   className = null;
221         try {
222             className = metadata.getColumnClassName(i);
223         } catch (SQLException   e) {
224             // this is a patch for HsqlDb to ignore exceptions
225             // thrown by its metadata implementation
226         }
227 
228         // Default to Object type if no class name could be retrieved
229         // from the metadata
230         Class   clazz = Object  .class;
231         if (className != null) {
232             clazz = loadClass(className);
233         }
234         return new DynaProperty(name, clazz);
235 
236     }
237 
238     /**
239      * <p>Introspect the metadata associated with our result set, and populate
240      * the <code>properties</code> and <code>propertiesMap</code> instance
241      * variables.</p>
242      *
243      * @param resultSet The <code>resultSet</code> whose metadata is to
244      *  be introspected
245      *
246      * @exception SQLException if an error is encountered processing the
247      *  result set metadata
248      */
249     protected void introspect(ResultSet   resultSet) throws SQLException   {
250 
251         // Accumulate an ordered list of DynaProperties
252         List   list = new ArrayList  ();
253         ResultSetMetaData   metadata = resultSet.getMetaData();
254         int n = metadata.getColumnCount();
255         for (int i = 1; i <= n; i++) { // JDBC is one-relative!
256             DynaProperty dynaProperty = createDynaProperty(metadata, i);
257             if (dynaProperty != null) {
258                     list.add(dynaProperty);
259             }
260         }
261 
262         // Convert this list into the internal data structures we need
263         properties =
264             (DynaProperty[]) list.toArray(new DynaProperty[list.size()]);
265         for (int i = 0; i < properties.length; i++) {
266             propertiesMap.put(properties[i].getName(), properties[i]);
267         }
268 
269     }
270 
271 }
272
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