TypeTag


1   /**
2    * C-JDBC: Clustered JDBC.
3    * Copyright (C) 2002-2005 Emic Networks
4    * Contact: c-jdbc@objectweb.org
5    * 
6    * This library is free software; you can redistribute it and/or modify it
7    * under the terms of the GNU Lesser General Public License as published by the
8    * Free Software Foundation; either version 2.1 of the License, or any later
9    * version.
10   * 
11   * This library is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
14   * for more details.
15   * 
16   * You should have received a copy of the GNU Lesser General Public License
17   * along with this library; if not, write to the Free Software Foundation,
18   * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
19   *
20   * Initial developer(s): Marc Herbert
21   * Contributor(s): ______________________.
22   */
23  
24  package org.objectweb.cjdbc.driver.protocol;
25  
26  import java.io.IOException  ;
27  import java.sql.Types  ;
28  
29  import org.objectweb.cjdbc.common.stream.CJDBCInputStream;
30  import org.objectweb.cjdbc.common.stream.CJDBCOutputStream;
31  
32  /**
33   * This class implements protocol type tags with an internal String, but offers
34   * an abstract interface on top of it in order to be transparently substituted
35   * some day (with enums for instance).
36   * <p>
37   * Advantages of using string types is human-readability (debugging, trace
38   * analysis, etc.) and earlier detection in case of protocol corruption.
39   * Drawback maybe a small performance cost.
40   * <p>
41   * Check "the importance of being textual" - by Eric S. Raymond.
42   * http://www.faqs.org/docs/artu/ch05s01.html
43   * 
44   * @author <a HREF="mailto:Marc.Herbert@emicnetworks.com">Marc Herbert </a>
45   * @version 1.0
46   */
47  public final class TypeTag
48  {
49    private String                internalString;
50  
51  
52    /** ** Actual Types *** */
53    private static final String   TPREFIX          = "T-";
54  
55    /* SQL "objects" */
56    /*
57     * The reference is table 47.9.3 "JDBC Types Mapped to Java Object Types" in
58     * 2nd edition (JDBC 2.1) of the book "JDBC API Tutorial and reference", or
59     * table 50.3 in the 3rd edition (JDBC 3.0). Also available online in Sun's
60     * "JDBC Technology Guide: Getting Started", section "Mapping SQL and Java
61     * Types".
62     */
63    /* unsupported are: DISTINCT, Array, Struct/SQLData, Ref, JAVA_OBJECT */
64    /* JDBC 3.0 added the type: java.net.URL, also currently unsupported */
65  
66    /** Constant for a SQL/Java type */
67    public static final TypeTag TYPE_ERROR       = new TypeTag(
68                                                     TPREFIX
69                                                         + "Type not found or unsupported");
70    /** Constant for a SQL/Java type */
71    public static final TypeTag STRING           = new TypeTag(TPREFIX + "String");
72    /** Constant for a SQL/Java type */
73    public static final TypeTag BIGDECIMAL       = new TypeTag(TPREFIX
74                                                     + "BigDecimal");
75    /** Constant for a SQL/Java type */
76    public static final TypeTag BOOLEAN          = new TypeTag(TPREFIX
77                                                     + "Boolean");
78    /** Constant for a SQL/Java type */
79    public static final TypeTag INTEGER          = new TypeTag(TPREFIX
80                                                     + "Integer");
81    /** Constant for a SQL/Java type */
82    public static final TypeTag LONG             = new TypeTag(TPREFIX + "Long");
83    /** Constant for a SQL/Java type */
84    public static final TypeTag FLOAT            = new TypeTag(TPREFIX + "Float");
85    /** Constant for a SQL/Java type */
86    public static final TypeTag DOUBLE           = new TypeTag(TPREFIX + "Double");
87    /** Constant for a SQL/Java type */
88    public static final TypeTag BYTE_ARRAY       = new TypeTag(TPREFIX + "Byte[]");
89    /** Constant for a SQL/Java type */
90    public static final TypeTag SQL_DATE         = new TypeTag(TPREFIX
91                                                     + "SqlDate");
92    /** Constant for a SQL/Java type */
93    public static final TypeTag SQL_TIME         = new TypeTag(TPREFIX
94                                                     + "SqlTime");
95    /** Constant for a SQL/Java type */
96    public static final TypeTag SQL_TIMESTAMP    = new TypeTag(TPREFIX
97                                                     + "SqlTimestamp");
98    /** Constant for a SQL/Java type */
99    public static final TypeTag CLOB             = new TypeTag(TPREFIX + "Clob");
100   /** Constant for a SQL/Java type */
101   public static final TypeTag BLOB             = new TypeTag(TPREFIX + "Blob");
102 
103   /* Structs */
104   
105   /** Constant for a SQL structure */
106   public static final TypeTag RESULTSET        = new TypeTag(TPREFIX
107                                                    + "ResultSet");
108   /** Null ResultSet */
109   public static final TypeTag NULL_RESULTSET   = new TypeTag("null ResultSet");
110 
111   /** Constant for a SQL structure */
112   public static final TypeTag FIELD            = new TypeTag(TPREFIX + "Field");
113   /** Constant for a SQL structure */
114   public static final TypeTag COL_TYPES        = new TypeTag(TPREFIX
115                                                    + "Column types");
116   /** Constant for a SQL structure */
117   public static final TypeTag ROW              = new TypeTag(TPREFIX + "Row");
118 
119   
120   /** used when there is no type ambiguity; no need to type */
121   public static final TypeTag NOT_EXCEPTION    = new TypeTag("OK");
122 
123   /** Constant for an exception */
124   public static final TypeTag EXCEPTION    = new TypeTag(TPREFIX
125                                                    + "Exception");
126   /** Constant for an exception */
127   public static final TypeTag BACKEND_EXCEPTION    = new TypeTag(TPREFIX
128                                                    + "BackendException");
129   /** Constant for an exception */
130   public static final TypeTag CORE_EXCEPTION  = new TypeTag(TPREFIX
131                                                    + "CoreException");
132 
133   /** Constant for internal protocol data */
134   public static final TypeTag CONTROLLER_READY = new TypeTag("Ready");
135 
136   private TypeTag(String   init)
137   {
138     this.internalString = init;
139   }
140 
141   /**
142    * Read/deserialize/construct a TypeTag from a stream.
143    * 
144    * @param in input stream
145    * @throws IOException stream error
146    */
147   public TypeTag(CJDBCInputStream in) throws IOException  
148   {
149     this(in.readUTF());
150   }
151 
152   /**
153    * Serialize "this" tag on the stream.
154    * 
155    * @param out output stream
156    * @throws IOException stream error
157    */
158   public void sendToStream(CJDBCOutputStream out) throws IOException  
159   {
160     out.writeUTF(this.internalString);
161   }
162 
163   /**
164    * Calling this method is a bug, check the type of your argument.
165    * 
166    * @param o compared object (which should be a TypeTag!)
167    * @return a buggy result
168    * @see java.lang.Object#equals(java.lang.Object)
169    * @deprecated
170    */
171   public boolean equals(Object   o)
172   {
173     System.err
174         .println("internal bug: TypeTag was compared with something else at:");
175     (new Throwable  ()).printStackTrace();
176     return false;
177   }
178 
179   /**
180    * Compares two TypeTags.
181    * 
182    * @param b compared TypeTag
183    * @return true if same value
184    */
185   public boolean equals(TypeTag b)
186   {
187     /**
188      * Even if the constants above are static, we cannot use "==" since we also
189      * have to consider objects built from the stream
190      * {@link #TypeTag(CJDBCInputStream)}
191      */
192     /*
193      * We could reimplement String.equals here without the instanceof in order
194      * to get back a couple of CPU cycles.
195      */
196     return this.internalString.equals(b.internalString);
197   }
198 
199   /**
200    * Returns a string representation, useful for logging and debugging.
201    * 
202    * @return string representation of the tag
203    */
204   public String   toSring()
205   {
206     return internalString;
207   }
208 
209   /**
210    * Gives the standard JDBC type to Java Object type conversion according to
211    * table "JDBC type to Java Object Type" of the JDBC reference book. (Table
212    * 47.9.3 in 2nd Edition, table 50.3 in 3rd edition). This is the conversion
213    * that the getObject() method of every JDBC driver should perform by default.
214    * 
215    * @param jdbcType the JDBC type to convert
216    * @return the Java Object type resulting from the standard type conversion.
217    * @see java.sql.Types
218    */
219 
220   public static TypeTag jdbcToJavaObjectType(int jdbcType)
221   {
222     switch (jdbcType)
223     {
224 
225       case Types.CHAR :
226       case Types.VARCHAR :
227       case Types.LONGVARCHAR :
228         return TypeTag.STRING;
229 
230       case Types.NUMERIC :
231       case Types.DECIMAL :
232         return TypeTag.BIGDECIMAL;
233 
234       case Types.BIT :
235         return TypeTag.BOOLEAN;
236 
237       case Types.TINYINT :
238       case Types.SMALLINT :
239       case Types.INTEGER :
240         return TypeTag.INTEGER;
241 
242       case Types.BIGINT :
243         return TypeTag.LONG;
244 
245       case Types.REAL :
246         return TypeTag.FLOAT;
247 
248       case Types.FLOAT :
249       case Types.DOUBLE :
250         return TypeTag.DOUBLE;
251 
252       case Types.BINARY :
253       case Types.VARBINARY :
254       case Types.LONGVARBINARY :
255         return TypeTag.BYTE_ARRAY;
256 
257       case Types.DATE :
258         return TypeTag.SQL_DATE;
259 
260       case Types.TIME :
261         return TypeTag.SQL_TIME;
262 
263       case Types.TIMESTAMP :
264         return TypeTag.SQL_TIMESTAMP;
265 
266       // DISTINCT unsupported
267 
268       case Types.CLOB :
269         return TypeTag.CLOB;
270 
271       case Types.BLOB :
272         return TypeTag.BLOB;
273 
274       // ARRAY, STRUCT/SQLData, REF, JAVA_OBJECT unsupported
275 
276       // JDBC 3.0 java.net.URL unsupported
277       
278       default :
279         return TypeTag.TYPE_ERROR;
280     }
281   }
282 }
283
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