Java tutorial
/* * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.sql.rowset.serial; import java.sql.*; import java.io.*; import java.util.Arrays; /** * 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. * * <h2> Thread safety </h2> * * <p> A SerialClob is not safe for use by multiple concurrent threads. If a * SerialClob is to be used by more than one thread then access to the SerialClob * should be controlled by appropriate synchronization. * * @author Jonathan Bruce * @since 1.5 */ 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 initialized with a * Clob. Null if SerialClob is initialized with a char[]. */ 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 this <code>SerialClob</code> * object's 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; clob = null; } /** * 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 must * return non-null for both 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 either of the * <code>Clob.getCharacterStream()</code> and <code>Clob.getAsciiStream()</code> * methods on the <code>Clob</code> returns 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; try (Reader charStream = clob.getCharacterStream()) { if (charStream == null) { throw new SQLException("Invalid Clob object. The call to getCharacterStream " + "returned null which cannot be serialized."); } // Note: get an ASCII stream in order to null-check it, // even though we don't do anything with it. try (InputStream asciiStream = clob.getAsciiStream()) { if (asciiStream == null) { throw new SQLException("Invalid Clob object. The call to getAsciiStream " + "returned null which cannot be serialized."); } } try (Reader reader = new BufferedReader(charStream)) { 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; * if {@code free} had previously been called on this object */ public long length() throws SerialException { isValid(); 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; * if {@code free} had previously been called on this object */ public java.io.Reader getCharacterStream() throws SerialException { isValid(); 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} object was not * instantiated with a <code>Clob</code> object; * if {@code free} had previously been called on this 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 { isValid(); 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; * if {@code free} had previously been called on this object */ public String getSubString(long pos, int length) throws SerialException { isValid(); if (pos < 1 || pos > this.length()) { throw new SerialException("Invalid position in SerialClob 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 * <code>-1</code> if the pattern is not found. * * @param searchStr the <code>String</code> object for which to * search * @param start the position in this <code>SerialClob</code> object * at which to start 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>SerialClob</code> object * @return the position at which the given <code>String</code> object * begins, starting the search at the specified position; * <code>-1</code> if the given <code>String</code> object is * not found or the starting position is out of bounds; position * numbering for the return value starts at <code>1</code> * @throws SerialException if the {@code free} method had been * previously called on this object * @throws SQLException if there is an error accessing the Clob value * from the database. */ public long position(String searchStr, long start) throws SerialException, SQLException { isValid(); if (start < 1 || start > len) { return -1; } char pattern[] = searchStr.toCharArray(); int pos = (int) start - 1; int i = 0; long patlen = pattern.length; while (pos < len) { if (pattern[i] == buf[pos]) { if (i + 1 == patlen) { return (pos + 1) - (patlen - 1); } i++; pos++; // increment pos, and i } else if (pattern[i] != buf[pos]) { pos++; // increment pos only } } return -1; // not found } /** * Returns the position in this <code>SerialClob</code> object * where the given <code>Clob</code> signature begins, starting * the search at the specified position. This method returns * <code>-1</code> if the pattern is not found. * * @param searchStr the <code>Clob</code> object for which to search * @param start the position in this <code>SerialClob</code> object * at 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>SerialClob</code> object * @return the position at which the given <code>Clob</code> * object begins in this <code>SerialClob</code> object, * at or after the specified starting position * @throws SerialException if an error occurs locating the Clob signature; * if the {@code free} method had been previously called on this object * @throws SQLException if there is an error accessing the Clob value * from the database */ public long position(Clob searchStr, long start) throws SerialException, SQLException { isValid(); return position(searchStr.getSubString(1, (int) searchStr.length()), start); } /** * Writes the given Java <code>String</code> to the <code>CLOB</code> * value that this <code>SerialClob</code> object represents, at the position * <code>pos</code>. * * @param pos the position at which to start writing to the <code>CLOB</code> * value that this <code>SerialClob</code> object represents; the first * position is <code>1</code>; must not be less than <code>1</code> nor * greater than the length of this <code>SerialClob</code> object * @param str the string to be written to the <code>CLOB</code> * value that this <code>SerialClob</code> object represents * @return the number of characters written * @throws SerialException if there is an error accessing the * <code>CLOB</code> value; if an invalid position is set; if an * invalid offset value is set; if number of bytes to be written * is greater than the <code>SerialClob</code> length; or the combined * values of the length and offset is greater than the Clob buffer; * if the {@code free} method had been previously called on this object */ public int setString(long pos, String str) throws SerialException { return (setString(pos, str, 0, str.length())); } /** * Writes <code>len</code> characters of <code>str</code>, starting * at character <code>offset</code>, to the <code>CLOB</code> value * that this <code>Clob</code> represents. * * @param pos the position at which to start writing to the <code>CLOB</code> * value that this <code>SerialClob</code> object represents; the first * position is <code>1</code>; must not be less than <code>1</code> nor * greater than the length of this <code>SerialClob</code> object * @param str the string to be written to the <code>CLOB</code> * value that this <code>Clob</code> object represents * @param offset the offset into <code>str</code> to start reading * the characters to be written * @param length the number of characters to be written * @return the number of characters written * @throws SerialException if there is an error accessing the * <code>CLOB</code> value; if an invalid position is set; if an * invalid offset value is set; if number of bytes to be written * is greater than the <code>SerialClob</code> length; or the combined * values of the length and offset is greater than the Clob buffer; * if the {@code free} method had been previously called on this object */ public int setString(long pos, String str, int offset, int length) throws SerialException { isValid(); String temp = str.substring(offset); char cPattern[] = temp.toCharArray(); if (offset < 0 || offset > str.length()) { throw new SerialException("Invalid offset in byte array set"); } if (pos < 1 || pos > this.length()) { throw new SerialException("Invalid position in Clob object set"); } if ((long) (length) > origLen) { throw new SerialException("Buffer is not sufficient to hold the value"); } if ((length + offset) > str.length()) { // need check to ensure length + offset !> bytes.length throw new SerialException("Invalid OffSet. Cannot have combined offset " + " and length that is greater that the Blob buffer"); } int i = 0; pos--; //values in the array are at position one less while (i < length || (offset + i + 1) < (str.length() - offset)) { this.buf[(int) pos + i] = cPattern[offset + i]; i++; } return i; } /** * Retrieves a stream to be used to write Ascii characters to the * <code>CLOB</code> value that this <code>SerialClob</code> object represents, * starting at position <code>pos</code>. This method forwards the * <code>setAsciiStream()</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. * * @param pos the position at which to start writing to the * <code>CLOB</code> object * @return the stream to which ASCII encoded characters can be written * @throws SerialException if SerialClob is not instantiated with a * Clob object; * if the {@code free} method had been previously called on this object * @throws SQLException if there is an error accessing the * <code>CLOB</code> value * @see #getAsciiStream */ public java.io.OutputStream setAsciiStream(long pos) throws SerialException, SQLException { isValid(); if (this.clob != null) { return this.clob.setAsciiStream(pos); } else { throw new SerialException("Unsupported operation. SerialClob cannot " + "return a writable ascii stream\n unless instantiated with a Clob object " + "that has a setAsciiStream() implementation"); } } /** * Retrieves a stream to be used to write a stream of Unicode characters * to the <code>CLOB</code> value that this <code>SerialClob</code> object * represents, at position <code>pos</code>. This method forwards the * <code>setCharacterStream()</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> is thrown. * * @param pos the position at which to start writing to the * <code>CLOB</code> value * * @return a stream to which Unicode encoded characters can be written * @throws SerialException if the SerialClob is not instantiated with * a Clob object; * if the {@code free} method had been previously called on this object * @throws SQLException if there is an error accessing the * <code>CLOB</code> value * @see #getCharacterStream */ public java.io.Writer setCharacterStream(long pos) throws SerialException, SQLException { isValid(); if (this.clob != null) { return this.clob.setCharacterStream(pos); } else { throw new SerialException("Unsupported operation. SerialClob cannot " + "return a writable character stream\n unless instantiated with a Clob object " + "that has a setCharacterStream implementation"); } } /** * Truncates the <code>CLOB</code> value that this <code>SerialClob</code> * object represents so that it has a length of <code>len</code> * characters. * <p> * Truncating a <code>SerialClob</code> object to length 0 has the effect of * clearing its contents. * * @param length the length, in bytes, to which the <code>CLOB</code> * value should be truncated * @throws SerialException if there is an error accessing the * <code>CLOB</code> value; * if the {@code free} method had been previously called on this object */ public void truncate(long length) throws SerialException { isValid(); if (length > len) { throw new SerialException("Length more than what can be truncated"); } else { len = length; // re-size the buffer if (len == 0) { buf = new char[] {}; } else { buf = (this.getSubString(1, (int) len)).toCharArray(); } } } /** * Returns a {@code Reader} object that contains a partial * {@code SerialClob} value, starting * with the character specified by pos, which is length characters in length. * * @param pos the offset to the first character of the partial value to * be retrieved. The first character in the {@code SerialClob} is at position 1. * @param length the length in characters of the partial value to be retrieved. * @return {@code Reader} through which the partial {@code SerialClob} * value can be read. * @throws SQLException if pos is less than 1 or if pos is greater than the * number of characters in the {@code SerialClob} or if pos + length * is greater than the number of characters in the {@code SerialClob}; * @throws SerialException if the {@code free} method had been previously * called on this object * @since 1.6 */ public Reader getCharacterStream(long pos, long length) throws SQLException { isValid(); if (pos < 1 || pos > len) { throw new SerialException("Invalid position in Clob object set"); } if ((pos - 1) + length > len) { throw new SerialException("Invalid position and substring length"); } if (length <= 0) { throw new SerialException("Invalid length specified"); } return new CharArrayReader(buf, (int) pos, (int) length); } /** * This method frees the {@code SerialClob} object and releases the * resources that it holds. * The object is invalid once the {@code free} method is called. * <p> * If {@code free} is called multiple times, the subsequent * calls to {@code free} are treated as a no-op. * </P> * @throws SQLException if an error occurs releasing * the Clob's resources * @since 1.6 */ public void free() throws SQLException { if (buf != null) { buf = null; if (clob != null) { clob.free(); } clob = null; } } /** * Compares this SerialClob to the specified object. The result is {@code * true} if and only if the argument is not {@code null} and is a {@code * SerialClob} object that represents the same sequence of characters as this * object. * * @param obj The object to compare this {@code SerialClob} against * * @return {@code true} if the given object represents a {@code SerialClob} * equivalent to this SerialClob, {@code false} otherwise * */ public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof SerialClob) { SerialClob sc = (SerialClob) obj; if (this.len == sc.len) { return Arrays.equals(buf, sc.buf); } } return false; } /** * Returns a hash code for this {@code SerialClob}. * @return a hash code value for this object. */ public int hashCode() { return ((31 + Arrays.hashCode(buf)) * 31 + (int) len) * 31 + (int) origLen; } /** * Returns a clone of this {@code SerialClob}. The copy will contain a * reference to a clone of the internal character array, not a reference * to the original internal character array of this {@code SerialClob} object. * The underlying {@code Clob} object will be set to null. * * @return a clone of this SerialClob */ public Object clone() { try { SerialClob sc = (SerialClob) super.clone(); sc.buf = (buf != null) ? Arrays.copyOf(buf, (int) len) : null; sc.clob = null; return sc; } catch (CloneNotSupportedException ex) { // this shouldn't happen, since we are Cloneable throw new InternalError(); } } /** * readObject is called to restore the state of the SerialClob from * a stream. */ private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException { ObjectInputStream.GetField fields = s.readFields(); char[] tmp = (char[]) fields.get("buf", null); if (tmp == null) throw new InvalidObjectException("buf is null and should not be!"); buf = tmp.clone(); len = fields.get("len", 0L); if (buf.length != len) throw new InvalidObjectException("buf is not the expected size"); origLen = fields.get("origLen", 0L); clob = (Clob) fields.get("clob", null); } /** * writeObject is called to save the state of the SerialClob * to a stream. */ private void writeObject(ObjectOutputStream s) throws IOException { ObjectOutputStream.PutField fields = s.putFields(); fields.put("buf", buf); fields.put("len", len); fields.put("origLen", origLen); // Note: this check to see if it is an instance of Serializable // is for backwards compatibility fields.put("clob", clob instanceof Serializable ? clob : null); s.writeFields(); } /** * Check to see if this object had previously had its {@code free} method * called * * @throws SerialException */ private void isValid() throws SerialException { if (buf == null) { throw new SerialException( "Error: You cannot call a method on a " + "SerialClob instance once free() has been called."); } } /** * The identifier that assists in the serialization of this {@code SerialClob} * object. */ static final long serialVersionUID = -1662519690087375313L; }