serialblob.java

Mobile 应用程序使用 Java Micro Edition (Java ME) 平台

/*
 * @(#)SerialBlob.java	1.11 06/04/07
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.sql.rowset.serial;

import java.sql.*;
import java.io.*;
import java.lang.reflect.*;


/**
 * A serialized mapping in the Java programming language of an SQL 
 * <code>BLOB</code> value. 
 * <P>
 * The <code>SerialBlob</code> class provides a constructor for creating
 * an instance from a <code>Blob</code> object.  Note that the 
 * <code>Blob</code>
 * object should have brought the SQL <code>BLOB</code> value's data over
 * to the client before a <code>SerialBlob</code> object
 * is constructed from it.  The data of an SQL <code>BLOB</code> value can
 * be materialized on the client as an array of bytes (using the method
 * <code>Blob.getBytes</code>) or as a stream of uninterpreted bytes
 * (using the method <code>Blob.getBinaryStream</code>).
 * <P>
 * <code>SerialBlob</code> methods make it possible to make a copy of a 
 * <code>SerialBlob</code> object as an array of bytes or as a stream.
 * They also make it possible to locate a given pattern of bytes or a
 * <code>Blob</code> object within a <code>SerialBlob</code> object
 * and to update or truncate a <code>Blob</code> object.
 *
 * @author Jonathan Bruce
 */
public class SerialBlob implements Blob, Serializable, Cloneable {
       
    /**	 
     * A serialized array of uninterpreted bytes representing the
     * value of this <code>SerialBlob</code> object.
     * @serial
     */
    private byte buf[];
    
    /**
     * The internal representation of the <code>Blob</code> object on which this
     * <code>SerialBlob</code> object is based.
     */
    private Blob blob;

    /**
     * The number of bytes in this <code>SerialBlob</code> object's
     * array of bytes.
     * @serial
     */
    private long len;
	
    /**
     * The orginal number of bytes in this <code>SerialBlob</code> object's
     * array of bytes when it was first established.
     * @serial
     */
    private long origLen;
        
    /**
     * Constructs a <code>SerialBlob</code> object that is a serialized version of
     * the given <code>byte</code> array.
     * <p>
     * The new <code>SerialBlob</code> object is initialized with the data from the
     * <code>byte</code> array, thus allowing disconnected <code>RowSet</code>
     * objects to establish serialized <code>Blob</code> objects without 
     * touching the data source.
     *
     * @param b the <code>byte</code> array containing the data for the 
     *        <code>Blob</code> object to be serialized
     * @throws SerialException if an error occurs during serialization
     * @throws SQLException if a SQL errors occurs
     */
    public SerialBlob(byte[] b) throws SerialException, SQLException {
    	
        len = b.length;                
        buf = new byte[(int)len];               
        for(int i = 0; i < len; i++) {
           buf[i] = b[i];
        }          
        origLen = len;
    }
    
       
    /** 	 
     * Constructs a <code>SerialBlob</code> object that is a serialized
     * version of the given <code>Blob</code> object. 
     * <P>
     * The new <code>SerialBlob</code> object is initialized with the
     * data from the <code>Blob</code> object; therefore, the 
     * <code>Blob</code> object should have previously brought the
     * SQL <code>BLOB</code> value's data over to the client from
     * the database. Otherwise, the new <code>SerialBlob</code> object
     * will contain no data.
     * 
     * @param blob the <code>Blob</code> object from which this
     *     <code>SerialBlob</code> object is to be constructed;
     *     cannot be null.
     * @throws SerialException if an error occurs during serialization
     * @throws SQLException if the <code>Blob</code> passed to this
     *     to this constructor is a <code>null</code>.
     * @see java.sql.Blob     
     */
    public SerialBlob (Blob blob) throws SerialException, SQLException {
    
        if (blob == null) {
            throw new SQLException("Cannot instantiate a SerialBlob " +
                 "object with a null Blob object");
        }
        
        len = blob.length();                       
        buf = blob.getBytes(1, (int)len );
        this.blob = blob;
        
         //if ( len < 10240000)
         // len = 10240000;          
        origLen = len;
    }
    
    /**
     * Copies the specified number of bytes, starting at the given
     * position, from this <code>SerialBlob</code> object to 
     * another array of bytes.
     * <P>
     * Note that if the given number of bytes to be copied is larger than
     * the length of this <code>SerialBlob</code> object's array of
     * bytes, the given number will be shortened to the array's length.
     *
     * @param pos the ordinal position of the first byte in this
     *            <code>SerialBlob</code> object to be copied;
     *            numbering starts at <code>1</code>; must not be less 
     *            than <code>1</code> and must be less than or equal
     *            to the length of this <code>SerialBlob</code> object
     * @param length the number of bytes to be copied 
     * @return an array of bytes that is a copy of a region of this
     *         <code>SerialBlob</code> object, starting at the given
     *         position and containing the given number of consecutive bytes
     * @throws SerialException if the given starting position is out of bounds
     */
    public byte[] getBytes(long pos, int length) throws SerialException {
        if (length > len) {
            length = (int)len;                
        }

        if (pos < 1 || length - pos < 0 ) {
            throw new SerialException("Invalid arguments: position cannot be less that 1");
        }      
        
        pos--; // correct pos to array index
      
        byte[] b = new byte[length];
        
        for (int i = 0; i < length; i++) {
            b[i] = this.buf[(int)pos];
            pos++;
        }
        return b;
    }
	
    /**
     * Retrieves the number of bytes in this <code>SerialBlob</code>
     * object's array of bytes.
     *
     * @return a <code>long</code> indicating the length in bytes of this
     *         <code>SerialBlob</code> object's array of bytes
     * @throws SerialException if an error occurs
     */
    public long length() throws SerialException {
        return len;
    }

    /**
     * Returns this <code>SerialBlob</code> object as an input stream.
     * Unlike the related method, <code>setBinaryStream</code>,
     * a stream is produced regardless of whether the <code>SerialBlob</code>
     * was created with a <code>Blob</code> object or a <code>byte</code> array.
     *
     * @return a <code>java.io.InputStream</code> object that contains
     *         this <code>SerialBlob</code> object's array of bytes
     * @throws SerialException if an error occurs     
     * @see #setBinaryStream
     */
    public java.io.InputStream getBinaryStream() throws SerialException {            
         InputStream stream = new ByteArrayInputStream(buf);
         return (java.io.InputStream)stream;
    }
	
    /** 	
     * Returns the position in this <code>SerialBlob</code> object where	
     * the given pattern of bytes begins, starting the search at the	
     * specified position.	
     *	
     * @param pattern the pattern of bytes for which to search 	
     * @param start the position of the byte in this	
     *              <code>SerialBlob</code> object from which to begin 	
     *              the search; the first position is <code>1</code>;	
     *              must not be less than <code>1</code> nor greater than	
     *              the length of this <code>SerialBlob</code> object	
     * @return the position in this <code>SerialBlob</code> object	
     *         where the given pattern begins, starting at the specified	
     *         position; <code>-1</code> if the pattern is not found
     *         or the given starting position is out of bounds; position
     *         numbering for the return value starts at <code>1</code>	
     * @throws SerialException if an error occurs when serializing the blob	
     * @throws SQLException if there is an error accessing the <code>BLOB</code>
     *         value from the database     
     */
    public long position(byte[] pattern, long start) 
                throws SerialException, SQLException {                
        if (start < 1 || start > len) {
            return -1;
        } 

        int pos = (int)start-1; // internally Blobs are stored as arrays.