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.lang.reflect.*; import java.util.Arrays; /** * 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. * * <h2> Thread safety </h2> * * <p> A SerialBlob is not safe for use by multiple concurrent threads. If a * SerialBlob is to be used by more than one thread then access to the SerialBlob * should be controlled by appropriate synchronization. * * @author Jonathan Bruce * @since 1.5 */ 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 original 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; 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; * if {@code free} had previously been called on this object */ public byte[] getBytes(long pos, int length) throws SerialException { isValid(); if (length > len) { length = (int) len; } if (pos < 1 || len - pos < 0) { throw new SerialException("Invalid arguments: position cannot be " + "less than 1 or greater than the length of the SerialBlob"); } 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; * if {@code free} had previously been called on this object */ public long length() throws SerialException { isValid(); 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; * if {@code free} had previously been called on this object * @see #setBinaryStream */ public java.io.InputStream getBinaryStream() throws SerialException { isValid(); InputStream stream = new ByteArrayInputStream(buf); return 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; * if {@code free} had previously been called on this object * @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 { isValid(); if (start < 1 || start > len) { return -1; } int pos = (int) start - 1; // internally Blobs are stored as arrays. 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>SerialBlob</code> object where * the given <code>Blob</code> object begins, starting the search at the * specified position. * * @param pattern the <code>Blob</code> object 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 <code>Blob</code> object 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; * if {@code free} had previously been called on this object * @throws SQLException if there is an error accessing the <code>BLOB</code> * value from the database */ public long position(Blob pattern, long start) throws SerialException, SQLException { isValid(); return position(pattern.getBytes(1, (int) (pattern.length())), start); } /** * Writes the given array of bytes to the <code>BLOB</code> value that * this <code>Blob</code> object represents, starting at position * <code>pos</code>, and returns the number of bytes written. * * @param pos the position in the SQL <code>BLOB</code> value at which * to start writing. 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. * @param bytes the array of bytes to be written to the <code>BLOB</code> * value that this <code>Blob</code> object represents * @return the number of bytes written * @throws SerialException if there is an error accessing the * <code>BLOB</code> value; or if an invalid position is set; if an * invalid offset value is set; * if {@code free} had previously been called on this object * @throws SQLException if there is an error accessing the <code>BLOB</code> * value from the database * @see #getBytes */ public int setBytes(long pos, byte[] bytes) throws SerialException, SQLException { return setBytes(pos, bytes, 0, bytes.length); } /** * Writes all or part of the given <code>byte</code> array to the * <code>BLOB</code> value that this <code>Blob</code> object represents * and returns the number of bytes written. * Writing starts at position <code>pos</code> in the <code>BLOB</code> * value; <i>len</i> bytes from the given byte array are written. * * @param pos the position in the <code>BLOB</code> object at which * to start writing. 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. * @param bytes the array of bytes to be written to the <code>BLOB</code> * value * @param offset the offset in the <code>byte</code> array at which * to start reading the bytes. The first offset position is * <code>0</code>; must not be less than <code>0</code> nor greater * than the length of the <code>byte</code> array * @param length the number of bytes to be written to the * <code>BLOB</code> value from the array of bytes <i>bytes</i>. * * @return the number of bytes written * @throws SerialException if there is an error accessing the * <code>BLOB</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>SerialBlob</code> length; or the combined * values of the length and offset is greater than the Blob buffer; * if {@code free} had previously been called on this object * @throws SQLException if there is an error accessing the <code>BLOB</code> * value from the database. * @see #getBytes */ public int setBytes(long pos, byte[] bytes, int offset, int length) throws SerialException, SQLException { isValid(); if (offset < 0 || offset > bytes.length) { throw new SerialException("Invalid offset in byte array set"); } if (pos < 1 || pos > this.length()) { throw new SerialException("Invalid position in BLOB object set"); } if ((long) (length) > origLen) { throw new SerialException("Buffer is not sufficient to hold the value"); } if ((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--; // correct to array indexing while (i < length || (offset + i + 1) < (bytes.length - offset)) { this.buf[(int) pos + i] = bytes[offset + i]; i++; } return i; } /** * Retrieves a stream that can be used to write to the <code>BLOB</code> * value that this <code>Blob</code> object represents. The stream begins * at position <code>pos</code>. This method forwards the * <code>setBinaryStream()</code> call to the underlying <code>Blob</code> in * the event that this <code>SerialBlob</code> object is instantiated with a * <code>Blob</code>. If this <code>SerialBlob</code> is instantiated with * a <code>byte</code> array, a <code>SerialException</code> is thrown. * * @param pos the position in the <code>BLOB</code> value at which * to start writing * @return a <code>java.io.OutputStream</code> object to which data can * be written * @throws SQLException if there is an error accessing the * <code>BLOB</code> value * @throws SerialException if the SerialBlob in not instantiated with a * <code>Blob</code> object that supports <code>setBinaryStream()</code>; * if {@code free} had previously been called on this object * @see #getBinaryStream */ public java.io.OutputStream setBinaryStream(long pos) throws SerialException, SQLException { isValid(); if (this.blob != null) { return this.blob.setBinaryStream(pos); } else { throw new SerialException("Unsupported operation. SerialBlob cannot " + "return a writable binary stream, unless instantiated with a Blob object " + "that provides a setBinaryStream() implementation"); } } /** * Truncates the <code>BLOB</code> value that this <code>Blob</code> * object represents to be <code>len</code> bytes in length. * * @param length the length, in bytes, to which the <code>BLOB</code> * value that this <code>Blob</code> object represents should be * truncated * @throws SerialException if there is an error accessing the Blob value; * or the length to truncate is greater that the SerialBlob length; * if {@code free} had previously been 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 if ((int) length == 0) { buf = new byte[0]; len = length; } else { len = length; buf = this.getBytes(1, (int) len); } } /** * Returns an * <code>InputStream</code> object that contains a partial * {@code Blob} value, starting with the byte specified by pos, which is * length bytes in length. * * @param pos the offset to the first byte of the partial value to be * retrieved. The first byte in the {@code Blob} is at position 1 * @param length the length in bytes of the partial value to be retrieved * @return * <code>InputStream</code> through which the partial {@code Blob} value can * be read. * @throws SQLException if pos is less than 1 or if pos is greater than the * number of bytes in the {@code Blob} or if pos + length is greater than * the number of bytes in the {@code Blob} * @throws SerialException if the {@code free} method had been previously * called on this object * * @since 1.6 */ public InputStream getBinaryStream(long pos, long length) throws SQLException { isValid(); if (pos < 1 || pos > this.length()) { throw new SerialException("Invalid position in BLOB object set"); } if (length < 1 || length > len - pos + 1) { throw new SerialException("length is < 1 or pos + length > total number of bytes"); } return new ByteArrayInputStream(buf, (int) pos - 1, (int) length); } /** * This method frees the {@code SerialBlob} 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 Blob's resources * @since 1.6 */ public void free() throws SQLException { if (buf != null) { buf = null; if (blob != null) { blob.free(); } blob = null; } } /** * Compares this SerialBlob to the specified object. The result is {@code * true} if and only if the argument is not {@code null} and is a {@code * SerialBlob} object that represents the same sequence of bytes as this * object. * * @param obj The object to compare this {@code SerialBlob} against * * @return {@code true} if the given object represents a {@code SerialBlob} * equivalent to this SerialBlob, {@code false} otherwise * */ public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof SerialBlob) { SerialBlob sb = (SerialBlob) obj; if (this.len == sb.len) { return Arrays.equals(buf, sb.buf); } } return false; } /** * Returns a hash code for this {@code SerialBlob}. * @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 SerialBlob}. The copy will contain a * reference to a clone of the internal byte array, not a reference * to the original internal byte array of this {@code SerialBlob} object. * The underlying {@code Blob} object will be set to null. * * @return a clone of this SerialBlob */ public Object clone() { try { SerialBlob sb = (SerialBlob) super.clone(); sb.buf = (buf != null) ? Arrays.copyOf(buf, (int) len) : null; sb.blob = null; return sb; } catch (CloneNotSupportedException ex) { // this shouldn't happen, since we are Cloneable throw new InternalError(); } } /** * readObject is called to restore the state of the SerialBlob from * a stream. */ private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException { ObjectInputStream.GetField fields = s.readFields(); byte[] tmp = (byte[]) 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); blob = (Blob) fields.get("blob", null); } /** * writeObject is called to save the state of the SerialBlob * 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("blob", blob instanceof Serializable ? blob : 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 " + "SerialBlob instance once free() has been called."); } } /** * The identifier that assists in the serialization of this * {@code SerialBlob} object. */ static final long serialVersionUID = -8144641928112860441L; }