ColumnInfo


1   /*
2    * Copyright 2002 (C) TJDO.
3    * All rights reserved.
4    *
5    * This software is distributed under the terms of the TJDO License version 1.0.
6    * See the terms of the TJDO License in the documentation provided with this software.
7    *
8    * $Id: ColumnInfo.java,v 1.6 2003/02/05 18:15:14 jackknifebarber Exp $
9    */
10  
11  package com.triactive.jdo.store;
12  
13  import java.io.PrintWriter  ;
14  import java.io.StringWriter  ;
15  import java.sql.DatabaseMetaData  ;
16  import java.sql.ResultSet  ;
17  import java.sql.SQLException  ;
18  import java.sql.Types  ;
19  import javax.jdo.JDOFatalDataStoreException;
20  
21  
22  /**
23   * Represents the metadata of a specific table column.  This class is
24   * basically a data structure that makes accessing the JDBC column metadata
25   * easier.  Each of the items returned by 
26   * {@link DatabaseMetaData#getColumns(String,String,String,String)}
27   * is represented by a public field in this class.
28   *
29   * Subclasses of ColumnInfo can be created on a per-DBMS basis to supply missing
30   * metadata or correct faulty metadata obtained from that DBMS's JDBC driver(s).
31   *
32   * @author <a HREF="mailto:mmartin5@austin.rr.com">Mike Martin</a>
33   * @version $Revision: 1.6 $
34   *
35   * @see StoreManager#getColumnInfo
36   * @see DatabaseAdapter#newColumnInfo
37   * @see DatabaseMetaData#getColumns
38   */
39  
40  class ColumnInfo
41  {
42      /**
43       * The table catalog, which may be <tt>null</tt>.
44       */
45      public String   tableCat;
46  
47      /**
48       * The table schema, which may be <tt>null</tt>.
49       */
50      public String   tableSchem;
51  
52      /**
53       * The table name.
54       */
55      public String   tableName;
56  
57      /**
58       * The column name.
59       */
60      public String   columnName;
61  
62      /**
63       * Indicates the JDBC (SQL) data type from {@link java.sql.Types}.
64       */
65      public short dataType;
66  
67      /**
68       * The local type name used by the data source.
69       */
70      public String   typeName;
71  
72      /**
73       * Indicates the column size.  For char or date types, this is the maximum
74       * number of characters; for numeric or decimal types, this is the precision.
75       */
76      public int columnSize;
77  
78      /**
79       * Indicates the number of fractional digits.
80       */
81      public int decimalDigits;
82  
83      /**
84       * Indicates the radix, which is typically either 10 or 2.
85       */
86      public int numPrecRadix;
87  
88      /**
89       * Indicates whether the column can be NULL.
90       *
91       * @see DatabaseMetaData#columnNoNulls
92       * @see DatabaseMetaData#columnNullable
93       * @see DatabaseMetaData#columnNullableUnknown
94       */
95      public int nullable;
96  
97      /**
98       * An explanatory comment on the column; may be <tt>null</tt>.
99       */
100     public String   remarks;
101 
102     /**
103      * The default value for the column; may be <tt>null</tt>.
104      */
105     public String   columnDef;
106 
107     /**
108      * Indicates the maximum number of bytes in the column (for char types
109      * only).
110      */
111     public int charOctetLength;
112 
113     /**
114      * Indicates the index of the column in its table; the first column is 1,
115      * the second column is 2, and so on.
116      */
117     public int ordinalPosition;
118 
119     /**
120      * Either "NO" indicating that the column definitely does not allow
121      * <tt>null</tt> values, "YES" indicating that the column might allow
122      * <tt>null</tt> values, or an empty string ("") indicating that nullability
123      * is unknown.
124      */
125     public String   isNullable;
126 
127 
128     private int hash = 0;
129 
130 
131     /**
132      * Constructs a column information object from the current row of the given
133      * result set.  The {@link ResultSet} object passed must have been obtained
134      * from a call to DatabaseMetaData.getColumns().
135      *
136      * <p>This method only retrieves the values from the current row; the caller
137      * is required to advance to the next row with {@link ResultSet#next}.
138      *
139      * @param rs    The result set returned from DatabaseMetaData.getColumns().
140      *
141      * @exception JDOFatalDataStoreException
142      *      if a column of column information could not be retrieved from the
143      *      result set.
144      */
145 
146     public ColumnInfo(ResultSet   rs) throws JDOFatalDataStoreException
147     {
148         try
149         {
150             tableCat        = rs.getString(1);
151             tableSchem      = rs.getString(2);
152             tableName       = rs.getString(3);
153             columnName      = rs.getString(4);
154             dataType        = rs.getShort(5);
155             typeName        = rs.getString(6);
156             columnSize      = rs.getInt(7);
157             decimalDigits   = rs.getInt(9);
158             numPrecRadix    = rs.getInt(10);
159             nullable        = rs.getInt(11);
160             remarks         = rs.getString(12);
161             columnDef       = rs.getString(13);
162             charOctetLength = rs.getInt(16);
163             ordinalPosition = rs.getInt(17);
164             isNullable      = rs.getString(18);
165         }
166         catch (SQLException   e)
167         {
168             throw new JDOFatalDataStoreException("Can't read JDBC metadata from result set", e);
169         }
170 
171         if (dataType == Types.OTHER)
172         {
173             /*
174              * This nonsense is for drivers (like Oracle's) that inexplicably
175              * declare some columns to be of type Types.OTHER when they should
176              * obviously know better.
177              */
178             String   upperTypeName = typeName.toUpperCase();
179 
180             if (upperTypeName.equals("BLOB"))
181                 dataType = Types.BLOB;
182             else if (upperTypeName.equals("CLOB"))
183                 dataType = Types.CLOB;
184             else if (upperTypeName.equals("FLOAT"))
185                 dataType = Types.FLOAT;
186             else if (upperTypeName.endsWith("LONGVARBINARY"))
187                 dataType = Types.LONGVARBINARY;
188             else if (upperTypeName.endsWith("LONGVARCHAR"))
189                 dataType = Types.LONGVARCHAR;
190         }
191     }
192 
193 
194     /**
195      * Constructs a column information object from its individual attributes.
196      *
197      * <p>This can be useful to subclasses and/or custom DatabaseAdapters that
198      * need to modify and/or correct the metadata returned by the JDBC driver.
199      */
200 
201     public ColumnInfo(String   tableCat,
202                       String   tableSchem,
203                       String   tableName,
204                       String   columnName,
205                       short dataType,
206                       String   typeName,
207                       int columnSize,
208                       int decimalDigits,
209                       int numPrecRadix,
210                       int nullable,
211                       String   remarks,
212                       String   columnDef,
213                       int charOctetLength,
214                       int ordinalPosition,
215                       String   isNullable)
216     {
217         this.tableCat        = tableCat;
218         this.tableSchem      = tableSchem;
219         this.tableName       = tableName;
220         this.columnName      = columnName;
221         this.dataType        = dataType;
222         this.typeName        = typeName;
223         this.columnSize      = columnSize;
224         this.decimalDigits   = decimalDigits;
225         this.numPrecRadix    = numPrecRadix;
226         this.nullable        = nullable;
227         this.remarks         = remarks;
228         this.columnDef       = columnDef;
229         this.charOctetLength = charOctetLength;
230         this.ordinalPosition = ordinalPosition;
231         this.isNullable      = isNullable;
232     }
233 
234 
235     /**
236      * Indicates whether some object is "equal to" this one.  Two <tt>ColumnInfo
237      * </tt> objects are considered equal if their catalog, schema, table, and
238      * column names are all equal.
239      *
240      * @param   obj     the reference object with which to compare
241      *
242      * @return  <tt>true</tt> if this object is equal to the obj argument;
243      *          <tt>false</tt> otherwise.
244      */
245 
246     public final boolean equals(Object   obj)
247     {
248         if (obj == this)
249             return true;
250 
251         if (!(obj instanceof ColumnInfo))
252             return false;
253 
254         ColumnInfo ci = (ColumnInfo)obj;
255 
256         return (tableCat   == null ? ci.tableCat   == null : tableCat.equals(ci.tableCat))
257             && (tableSchem == null ? ci.tableSchem == null : tableSchem.equals(ci.tableSchem))
258             && tableName.equals(ci.tableName)
259             && columnName.equals(ci.columnName);
260     }
261 
262 
263     /**
264      * Returns a hash code value for this object.
265      *
266      * @return  a hash code value for this object.
267      */
268 
269     public final int hashCode()
270     {
271         if (hash == 0)
272         {
273             hash = (tableCat   == null ? 0 : tableCat.hashCode())
274                  ^ (tableSchem == null ? 0 : tableSchem.hashCode())
275                  ^ tableName.hashCode()
276                  ^ columnName.hashCode();
277         }
278 
279         return hash;
280     }
281 
282 
283     /**
284      * Returns the string representation of this object.
285      *
286      * @return  string representation of this object.
287      */
288 
289     public String   toString()
290     {
291         StringWriter   sw = new StringWriter  ();
292         PrintWriter    pw = new PrintWriter  (sw);
293 
294         pw.println(this.getClass().getName());
295         pw.print("  tableCat        = "); pw.println(tableCat);
296         pw.print("  tableSchem      = "); pw.println(tableSchem);
297         pw.print("  tableName       = "); pw.println(tableName);
298         pw.print("  columnName      = "); pw.println(columnName);
299         pw.print("  dataType        = "); pw.println(dataType);
300         pw.print("  typeName        = "); pw.println(typeName);
301         pw.print("  columnSize      = "); pw.println(columnSize);
302         pw.print("  decimalDigits   = "); pw.println(decimalDigits);
303         pw.print("  numPrecRadix    = "); pw.println(numPrecRadix);
304         pw.print("  nullable        = "); pw.println(nullable);
305         pw.print("  remarks         = "); pw.println(remarks);
306         pw.print("  columnDef       = "); pw.println(columnDef);
307         pw.print("  charOctetLength = "); pw.println(charOctetLength);
308         pw.print("  ordinalPosition = "); pw.println(ordinalPosition);
309         pw.print("  isNullable      = "); pw.println(isNullable);
310         pw.close();
311 
312         return sw.toString();
313     }
314 }
315
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