JDK8/Java8源码在线阅读
/*
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* 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.
*
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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.
*
* <h3> Thread safety </h3>
*
* <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
*/
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;
//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;
* 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 SeriableBlob} 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
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