serialclob.java

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

/*
 * @(#)SerialClob.java	1.17 07/06/25
 *
 * 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.*;

/**
 * A serialized mapping in the Java programming language of an SQL
 * <code>CLOB</code> value.
 * <P>
 * The <code>SerialClob</code> class provides a constructor for creating
 * an instance from a <code>Clob</code> object.  Note that the <code>Clob</code>
 * object should have brought the SQL <code>CLOB</code> value's data over
 * to the client before a <code>SerialClob</code> object
 * is constructed from it.  The data of an SQL <code>CLOB</code> value can
 * be materialized on the client as a stream of Unicode characters.
 * <P>
 * <code>SerialClob</code> methods make it possible to get a substring
 * from a <code>SerialClob</code> object or to locate the start of
 * a pattern of characters.
 *
 * @author Jonathan Bruce
 */
public class SerialClob implements Clob, Serializable, Cloneable {

    /**
     * A serialized array of characters containing the data of the SQL
     * <code>CLOB</code> value that this <code>SerialClob</code> object
     * represents.
     *
     * @serial
     */
    private char buf[];
    
    /**
     * Internal Clob representation if SerialClob is intialized with a
     * Clob
     */
    private Clob clob;
    
    /**
     * The length in characters of this <code>SerialClob</code> object's
     * internal array of characters.
     *
     * @serial
     */
    private long len;
    
    /**
     * The original length in characters of tgus <code>SerialClob</code> 
     * objects internal array of characters.
     * 
     * @serial
     */
    private long origLen;          
    
    /**
     * Constructs a <code>SerialClob</code> object that is a serialized version of
     * the given <code>char</code> array.
     * <p>
     * The new <code>SerialClob</code> object is initialized with the data from the
     * <code>char</code> array, thus allowing disconnected <code>RowSet</code>
     * objects to establish a serialized <code>Clob</code> object without touching
     * the data source.
     *
     * @param ch the char array representing the <code>Clob</code> object to be
     *         serialized
     * @throws SerialException if an error occurs during serialization
     * @throws SQLException if a SQL error occurs
     */
    public SerialClob(char ch[]) throws SerialException, SQLException {
                        
        // %%% JMB. Agreed. Add code here to throw a SQLException if no 
        // support is available for locatorsUpdateCopy=false
        // Serializing locators is not supported.
        
        len = ch.length;        
        buf = new char[(int)len];                
        for (int i = 0; i < len ; i++){
           buf[i] = ch[i];
        }                                
        origLen = len;
    }
    
    /**
     * Constructs a <code>SerialClob</code> object that is a serialized
     * version of the given <code>Clob</code> object.
     * <P>
     * The new <code>SerialClob</code> object is initialized with the
     * data from the <code>Clob</code> object; therefore, the
     * <code>Clob</code> object should have previously brought the
     * SQL <code>CLOB</code> value's data over to the client from
     * the database. Otherwise, the new <code>SerialClob</code> object
     * object will contain no data.
     * <p>
     * Note: The <code>Clob</code> object supplied to this constructor cannot
     * return <code>null</code> for the <code>Clob.getCharacterStream()</code> 
     * and <code>Clob.getAsciiStream</code> methods. This <code>SerialClob</code> 
     * constructor cannot  serialize a <code>Clob</code> object in this instance
     * and will throw an <code>SQLException</code> object.
     *
     * @param  clob the <code>Clob</code> object from which this
     *     <code>SerialClob</code> object is to be constructed; cannot be null
     * @throws SerialException if an error occurs during serialization
     * @throws SQLException if a SQL error occurs in capturing the CLOB;
     *     if the <code>Clob</code> object is a null; or if both the 
     *     <code>Clob.getCharacterStream()</code> and <code>Clob.getAsciiStream()</code>
     *     methods on the <code>Clob</code> return a null
     * @see java.sql.Clob
     */
    public SerialClob(Clob clob) throws SerialException, SQLException {         
        
        if (clob == null) {
            throw new SQLException("Cannot instantiate a SerialClob " +
                "object with a null Clob object");
        }                            
        len = clob.length(); 
        this.clob = clob;
        buf = new char[(int)len];
        int read = 0;
        int offset = 0;
        
        BufferedReader reader;
        if ( (((reader = new BufferedReader(clob.getCharacterStream())) == null)) && 
            (clob.getAsciiStream() == null)) {
            throw new SQLException("Invalid Clob object. Calls to getCharacterStream " +
                "and getAsciiStream return null which cannot be serialized.");
        }
        
        try {
            do {
                read = reader.read(buf, offset, (int)(len - offset));
                offset += read;
            } while (read > 0);        
            
        } catch (java.io.IOException ex) {
            throw new SerialException("SerialClob: " + ex.getMessage());
        }
                
        origLen = len;
    }

    /**
     * Retrieves the number of characters in this <code>SerialClob</code>
     * object's array of characters. 
     *
     * @return a <code>long</code> indicating the length in characters of this
     *         <code>SerialClob</code> object's array of character
     * @throws SerialException if an error occurs
     */
    public long length() throws SerialException {
        return len;
    }

    /**
     * Returns this <code>SerialClob</code> object's data as a stream
     * of Unicode characters. Unlike the related method, <code>getAsciiStream</code>,
     * a stream is produced regardless of whether the <code>SerialClob</code> object
     * was created with a <code>Clob</code> object or a <code>char</code> array.
     *
     * @return a <code>java.io.Reader</code> object containing this
     *         <code>SerialClob</code> object's data
     * @throws SerialException if an error occurs
     */
    public java.io.Reader getCharacterStream() throws SerialException {
        return (java.io.Reader) new CharArrayReader(buf);
    }
    
    /**
     * Retrieves the <code>CLOB</code> value designated by this <code>SerialClob</code>
     * object as an ascii stream. This method forwards the <code>getAsciiStream</code>
     * call to the underlying <code>Clob</code> object in the event that this 
     * <code>SerialClob</code> object is instantiated with a <code>Clob</code>
     * object. If this <code>SerialClob</code> object is instantiated with
     * a <code>char</code> array, a <code>SerialException</code> object is thrown.
     *
     * @return a <code>java.io.InputStream</code> object containing
     *     this <code>SerialClob</code> object's data
     * @throws SerialException if this <code>SerialClob</code> object was not instantiated
     *     with a <code>Clob</code> object
     * @throws SQLException if there is an error accessing the 
     *     <code>CLOB</code> value represented by the <code>Clob</code> object that was
     *     used to create this <code>SerialClob</code> object
     */
    public java.io.InputStream getAsciiStream() throws SerialException, SQLException {
       if (this.clob != null) {
             return this.clob.getAsciiStream();
         } else {
             throw new SerialException("Unsupported operation. SerialClob cannot " +
                "return a the CLOB value as an ascii stream, unless instantiated " +
                "with a fully implemented Clob object.");
         }       
    }

    /**
     * Returns a copy of the substring contained in this
     * <code>SerialClob</code> object, starting at the given position
     * and continuing for the specified number or characters.
     *
     * @param pos the position of the first character in the substring
     *            to be copied; the first character of the
     *            <code>SerialClob</code> object is at position
     *            <code>1</code>; must not be less than <code>1</code>,
     *            and the sum of the starting position and the length
     *            of the substring must be less than the length of this
     *            <code>SerialClob</code> object
     * @param length the number of characters in the substring to be
     *               returned; must not be greater than the length of
     *               this <code>SerialClob</code> object, and the
     *               sum of the starting position and the length
     *               of the substring must be less than the length of this
     *               <code>SerialClob</code> object
     * @return a <code>String</code> object containing a substring of
     *         this <code>SerialClob</code> object beginning at the
     *         given position and containing the specified number of
     *         consecutive characters
     * @throws SerialException if either of the arguments is out of bounds       
     */
    public String getSubString(long pos, int length) throws SerialException {        
       
        if (pos < 1 || pos > this.length()) {
            throw new SerialException("Invalid position in BLOB object set");
        }
        
        if ((pos-1) + length > this.length()) {
            throw new SerialException("Invalid position and substring length");
        }
        
        try {
            return new String(buf, (int)pos - 1, length);
            
        } catch (StringIndexOutOfBoundsException e) {
            throw new SerialException("StringIndexOutOfBoundsException: " +
                e.getMessage());
        }
            
    }

    /**
     * Returns the position in this <code>SerialClob</code> object
     * where the given <code>String</code> object begins, starting
     * the search at the specified position. This method returns