SerialBlob


1   /*
2    * @(#)SerialBlob.java  1.8 04/05/29
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.sql.rowset.serial;
9   
10  import java.sql.*;
11  import java.io.*;
12  import java.lang.reflect.*;
13  
14  
15  /**
16   * A serialized mapping in the Java programming language of an SQL 
17   * <code>BLOB</code> value. 
18   * <P>
19   * The <code>SerialBlob</code> class provides a constructor for creating
20   * an instance from a <code>Blob</code> object.  Note that the 
21   * <code>Blob</code>
22   * object should have brought the SQL <code>BLOB</code> value's data over
23   * to the client before a <code>SerialBlob</code> object
24   * is constructed from it.  The data of an SQL <code>BLOB</code> value can
25   * be materialized on the client as an array of bytes (using the method
26   * <code>Blob.getBytes</code>) or as a stream of uninterpreted bytes
27   * (using the method <code>Blob.getBinaryStream</code>).
28   * <P>
29   * <code>SerialBlob</code> methods make it possible to make a copy of a 
30   * <code>SerialBlob</code> object as an array of bytes or as a stream.
31   * They also make it possible to locate a given pattern of bytes or a
32   * <code>Blob</code> object within a <code>SerialBlob</code> object
33   * and to update or truncate a <code>Blob</code> object.
34   *
35   * @author Jonathan Bruce
36   */
37  public class SerialBlob implements Blob, Serializable, Cloneable   {
38         
39      /**  
40       * A serialized array of uninterpreted bytes representing the
41       * value of this <code>SerialBlob</code> object.
42       * @serial
43       */
44      private byte buf[];
45      
46      /**
47       * The internal representation of the <code>Blob</code> object on which this
48       * <code>SerialBlob</code> object is based.
49       */
50      private Blob blob;
51  
52      /**
53       * The number of bytes in this <code>SerialBlob</code> object's
54       * array of bytes.
55       * @serial
56       */
57      private long len;
58      
59      /**
60       * The orginal number of bytes in this <code>SerialBlob</code> object's
61       * array of bytes when it was first established.
62       * @serial
63       */
64      private long origLen;
65          
66      /**
67       * Constructs a <code>SerialBlob</code> object that is a serialized version of
68       * the given <code>byte</code> array.
69       * <p>
70       * The new <code>SerialBlob</code> object is initialized with the data from the
71       * <code>byte</code> array, thus allowing disconnected <code>RowSet</code>
72       * objects to establish serialized <code>Blob</code> objects without 
73       * touching the data source.
74       *
75       * @param b the <code>byte</code> array containing the data for the 
76       *        <code>Blob</code> object to be serialized
77       * @throws SerialException if an error occurs during serialization
78       * @throws SQLException if a SQL errors occurs
79       */
80      public SerialBlob(byte[] b) throws SerialException  , SQLException {
81          
82          len = b.length;                
83          buf = new byte[(int)len];               
84          for(int i = 0; i < len; i++) {
85             buf[i] = b[i];
86          }          
87          origLen = len;
88      }
89      
90         
91      /**      
92       * Constructs a <code>SerialBlob</code> object that is a serialized
93       * version of the given <code>Blob</code> object. 
94       * <P>
95       * The new <code>SerialBlob</code> object is initialized with the
96       * data from the <code>Blob</code> object; therefore, the 
97       * <code>Blob</code> object should have previously brought the
98       * SQL <code>BLOB</code> value's data over to the client from
99       * the database. Otherwise, the new <code>SerialBlob</code> object
100      * will contain no data.
101      * 
102      * @param blob the <code>Blob</code> object from which this
103      *     <code>SerialBlob</code> object is to be constructed;
104      *     cannot be null.
105      * @throws SerialException if an error occurs during serialization
106      * @throws SQLException if the <code>Blob</code> passed to this
107      *     to this constructor is a <code>null</code>.
108      * @see java.sql.Blob     
109      */
110     public SerialBlob (Blob blob) throws SerialException  , SQLException {
111     
112         if (blob == null) {
113             throw new SQLException("Cannot instantiate a SerialBlob " +
114                  "object with a null Blob object");
115         }
116         
117         len = blob.length();                       
118         buf = blob.getBytes(1, (int)len );
119         this.blob = blob;
120         
121          //if ( len < 10240000)
122          // len = 10240000;          
123         origLen = len;
124     }
125     
126     /**
127      * Copies the specified number of bytes, starting at the given
128      * position, from this <code>SerialBlob</code> object to 
129      * another array of bytes.
130      * <P>
131      * Note that if the given number of bytes to be copied is larger than
132      * the length of this <code>SerialBlob</code> object's array of
133      * bytes, the given number will be shortened to the array's length.
134      *
135      * @param pos the ordinal position of the first byte in this
136      *            <code>SerialBlob</code> object to be copied;
137      *            numbering starts at <code>1</code>; must not be less 
138      *            than <code>1</code> and must be less than or equal
139      *            to the length of this <code>SerialBlob</code> object
140      * @param length the number of bytes to be copied 
141      * @return an array of bytes that is a copy of a region of this
142      *         <code>SerialBlob</code> object, starting at the given
143      *         position and containing the given number of consecutive bytes
144      * @throws SerialException if the given starting position is out of bounds
145      */
146     public byte[] getBytes(long pos, int length) throws SerialException   {
147         if (length > len) {
148             length = (int)len;                
149         }
150 
151         if (pos < 1 || length - pos < 0 ) {
152             throw new SerialException  ("Invalid arguments: position cannot be less that 1");
153         }      
154         
155         pos--; // correct pos to array index
156       
157         byte[] b = new byte[length];
158         
159         for (int i = 0; i < length; i++) {
160             b[i] = this.buf[(int)pos];
161             pos++;
162         }
163         return b;
164     }
165     
166     /**
167      * Retrieves the number of bytes in this <code>SerialBlob</code>
168      * object's array of bytes.
169      *
170      * @return a <code>long</code> indicating the length in bytes of this
171      *         <code>SerialBlob</code> object's array of bytes
172      * @throws SerialException if an error occurs
173      */
174     public long length() throws SerialException   {
175         return len;
176     }
177 
178     /**
179      * Returns this <code>SerialBlob</code> object as an input stream.
180      * Unlike the related method, <code>setBinaryStream</code>,
181      * a stream is produced regardless of whether the <code>SerialBlob</code>
182      * was created with a <code>Blob</code> object or a <code>byte</code> array.
183      *
184      * @return a <code>java.io.InputStream</code> object that contains
185      *         this <code>SerialBlob</code> object's array of bytes
186      * @throws SerialException if an error occurs     
187      * @see #setBinaryStream
188      */
189     public java.io.InputStream   getBinaryStream() throws SerialException   {            
190          InputStream stream = new ByteArrayInputStream(buf);
191          return (java.io.InputStream  )stream;
192     }
193     
194     /**     
195      * Returns the position in this <code>SerialBlob</code> object where    
196      * the given pattern of bytes begins, starting the search at the    
197      * specified position.  
198      *  
199      * @param pattern the pattern of bytes for which to search  
200      * @param start the position of the byte in this    
201      *              <code>SerialBlob</code> object from which to begin  
202      *              the search; the first position is <code>1</code>;   
203      *              must not be less than <code>1</code> nor greater than   
204      *              the length of this <code>SerialBlob</code> object   
205      * @return the position in this <code>SerialBlob</code> object  
206      *         where the given pattern begins, starting at the specified    
207      *         position; <code>-1</code> if the pattern is not found
208      *         or the given starting position is out of bounds; position
209      *         numbering for the return value starts at <code>1</code>  
210      * @throws SerialException if an error occurs when serializing the blob 
211      * @throws SQLException if there is an error accessing the <code>BLOB</code>
212      *         value from the database     
213      */
214     public long position(byte[] pattern, long start) 
215                 throws SerialException  , SQLException {                
216         if (start < 1 || start > len) {
217             return -1;
218         } 
219 
220         int pos = (int)start-1; // internally Blobs are stored as arrays. 
221         int i = 0;        
222         long patlen = pattern.length;                
223         
224         while (pos < len) {     
225             if (pattern[i] == buf[pos]) {                
226                 if (i + 1 == patlen) {
227                     return (pos + 1) - (patlen - 1);
228                 }
229                 i++; pos++; // increment pos, and i
230             } else if (pattern[i] != buf[pos]) {
231                 pos++; // increment pos only
232             }                                    
233         }        
234         return -1; // not found
235     }
236         
237     /**      
238      * Returns the position in this <code>SerialBlob</code> object where    
239      * the given <code>Blob</code> object begins, starting the search at the    
240      * specified position.  
241      *  
242      * @param pattern the <code>Blob</code> object for which to search;     
243      * @param start the position of the byte in this    
244      *              <code>SerialBlob</code> object from which to begin  
245      *              the search; the first position is <code>1</code>;   
246      *              must not be less than <code>1</code> nor greater than   
247      *              the length of this <code>SerialBlob</code> object   
248      * @return the position in this <code>SerialBlob</code> object  
249      *         where the given <code>Blob</code> object begins, starting    
250      *         at the specified position; <code>-1</code> if the pattern is 
251      *         not found or the given starting position is out of bounds;        
252      *         position numbering for the return value starts at <code>1</code>     
253      * @throws SerialException if an error occurs when serializing the blob
254      * @throws SQLException if there is an error accessing the <code>BLOB</code>
255      *         value from the database     
256      */
257     public long position(Blob pattern, long start) 
258        throws SerialException  , SQLException {
259         return position(pattern.getBytes(1, (int)(pattern.length())), start);
260     }
261     
262     /**
263      * Writes the given array of bytes to the <code>BLOB</code> value that
264      * this <code>Blob</code> object represents, starting at position 
265      * <code>pos</code>, and returns the number of bytes written.
266      *
267      * @param pos the position in the SQL <code>BLOB</code> value at which
268      *     to start writing. The first position is <code>1</code>;  
269      *     must not be less than <code>1</code> nor greater than    
270      *     the length of this <code>SerialBlob</code> object.
271      * @param bytes the array of bytes to be written to the <code>BLOB</code>
272      *        value that this <code>Blob</code> object represents
273      * @return the number of bytes written
274      * @throws SerialException if there is an error accessing the
275      *     <code>BLOB</code> value; or if an invalid position is set; if an 
276      *     invalid offset value is set
277      * @throws SQLException if there is an error accessing the <code>BLOB</code>
278      *         value from the database     
279      * @see #getBytes
280      */
281     public int setBytes(long pos, byte[] bytes) 
282         throws SerialException  , SQLException {
283         return (setBytes(pos, bytes, 0, bytes.length));
284     }
285     
286     /**
287      * Writes all or part of the given <code>byte</code> array to the
288      * <code>BLOB</code> value that this <code>Blob</code> object represents
289      * and returns the number of bytes written.
290      * Writing starts at position <code>pos</code> in the <code>BLOB</code>
291      * value; <i>len</i> bytes from the given byte array are written.
292      *
293      * @param pos the position in the <code>BLOB</code> object at which
294      *     to start writing. The first position is <code>1</code>;  
295      *     must not be less than <code>1</code> nor greater than    
296      *     the length of this <code>SerialBlob</code> object.
297      * @param bytes the array of bytes to be written to the <code>BLOB</code>
298      *     value
299      * @param offset the offset in the <code>byte</code> array at which
300      *     to start reading the bytes. The first offset position is
301      *     <code>0</code>; must not be less than <code>0</code> nor greater
302      *     than the length of the <code>byte</code> array
303      * @param length the number of bytes to be written to the 
304      *     <code>BLOB</code> value from the array of bytes <i>bytes</i>.
305      *        
306      * @return the number of bytes written
307      * @throws SerialException if there is an error accessing the 
308      *     <code>BLOB</code> value; if an invalid position is set; if an 
309      *     invalid offset value is set; if number of bytes to be written
310      *     is greater than the <code>SerialBlob</code> length; or the combined
311      *     values of the length and offset is greater than the Blob buffer
312      * @throws SQLException if there is an error accessing the <code>BLOB</code>
313      *         value from the database.     
314      * @see #getBytes
315      */
316     public int setBytes(long pos, byte[] bytes, int offset, int length) 
317         throws SerialException  , SQLException {
318         
319         if (offset < 0 || offset > bytes.length) {
320             throw new SerialException  ("Invalid offset in byte array set");
321         }            
322         
323         if (pos < 1 || pos > this.length()) {
324             throw new SerialException  ("Invalid position in BLOB object set");
325         }
326                     
327         if ((long)(length) > origLen) {
328         throw new SerialException  ("Buffer is not sufficient to hold the value");
329     }    
330         
331         if ((length + offset) > bytes.length) {  
332             throw new SerialException  ("Invalid OffSet. Cannot have combined offset " +
333                 "and length that is greater that the Blob buffer");            
334         }                                       
335         
336         int i = 0;
337         pos--; // correct to array indexing
338         while ( i < length || (offset + i +1) < (bytes.length-offset) ) {
339             this.buf[(int)pos + i] = bytes[offset + i ]; 
340             i++;
341         }
342         return i;        
343     }
344     
345     /**
346      * Retrieves a stream that can be used to write to the <code>BLOB</code> 
347      * value that this <code>Blob</code> object represents.  The stream begins
348      * at position <code>pos</code>. This method forwards the 
349      * <code>setBinaryStream()</code> call to the underlying <code>Blob</code> in 
350      * the event that this <code>SerialBlob</code> object is instantiated with a 
351      * <code>Blob</code>. If this <code>SerialBlob</code> is instantiated with
352      * a <code>byte</code> array, a <code>SerialException</code> is thrown.
353      *
354      * @param pos the position in the <code>BLOB</code> value at which
355      *        to start writing
356      * @return a <code>java.io.OutputStream</code> object to which data can 
357      *         be written
358      * @throws SQLException if there is an error accessing the
359      *            <code>BLOB</code> value
360      * @throws SerialException if the SerialBlob in not instantiated with a 
361      *     <code>Blob</code> object that supports <code>setBinaryStream()</code>
362      * @see #getBinaryStream
363      */
364     public java.io.OutputStream   setBinaryStream(long pos) 
365         throws SerialException  , SQLException {       
366         if (this.blob.setBinaryStream(pos) != null) {
367             return this.blob.setBinaryStream(pos);
368         } else {
369             throw new SerialException  ("Unsupported operation. SerialBlob cannot " +
370                 "return a writable binary stream, unless instantiated with a Blob object " +
371                 "that provides a setBinaryStream() implementation");
372         }        
373     }
374     
375     /**
376      * Truncates the <code>BLOB</code> value that this <code>Blob</code>
377      * object represents to be <code>len</code> bytes in length.
378      *
379      * @param length the length, in bytes, to which the <code>BLOB</code>
380      *        value that this <code>Blob</code> object represents should be 
381      *        truncated
382      * @throws SerialException if there is an error accessing the Blob value;
383      *     or the length to truncate is greater that the SerialBlob length     
384      */
385     public void truncate(long length) throws SerialException   {
386          
387          if (length > len) {
388             throw new SerialException  
389                ("Length more than what can be truncated");
390          } else if((int)length == 0) { 
391               buf = new byte[0];
392               len = length;
393          } else {      
394               len = length;              
395               buf = this.getBytes(1, (int)len);
396          }  
397     }
398 
399     
400     /**
401      * The identifier that assists in the serialization of this <code>SerialBlob</code>
402      * object.
403      */
404 
405     static final long serialVersionUID = -8144641928112860441L;
406 }
407
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