/*
Derby - Class org.apache.derby.client.am.UpdateSensitiveBlobLocatorInputStream
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package org.apache.derby.client.am;
import java.io.BufferedInputStream;
import java.io.InputStream;
/**
* This class extends from the UpdateSensitiveLOBLocatorInputStream
* and creates and returns an implementation of the Blob specific
* locator InputStream. It also over-rides the reCreateStream method
* which re-creates the underlying Blob locator stream whenever a
* update happens on the Blob object associated with this stream.
*/
public class UpdateSensitiveBlobLocatorInputStream
extends UpdateSensitiveLOBLocatorInputStream {
//Stores the Blob instance associated with
//this InputStream.
private Blob blob = null;
/**
* Creates an instance of the BlobLocatorInputStream
* and and calls the super class constructors with
* appropriate initializers.
*
* @param con connection to be used to read the
* <code>Blob</code> value from the server
* @param blob <code>Blob</code> object that contains locator for
* the <code>Blob</code> value on the server.
*
* @throws SqlException If any exception occurs during stream
* creation.
*/
public UpdateSensitiveBlobLocatorInputStream(Connection con, Blob blob)
throws SqlException {
super(con, blob, new BlobLocatorInputStream(con, blob));
this.blob = blob;
}
/**
* Creates an instance of the BlobLocatorInputStream.
*
* @param con connection to be used to read the
* <code>Blob</code> value from the server
* @param blob <code>Blob</code> object that contains locator for
* the <code>Blob</code> value on the server.
* @param position the position in the <code>Blob</code> of the first
* byte to read.
* @param length the maximum number of bytes to read from
* the <code>Blob</code>.
*
* @throws SqlException If any exception occurs during stream
* creation.
*/
public UpdateSensitiveBlobLocatorInputStream(Connection con, Blob blob,
long position, long length) throws SqlException {
super(con, blob,
new BlobLocatorInputStream(con, blob, position, length),
position, length);
this.blob = blob;
}
/**
* Re-creates the underlying Locator stream
* with the current position and the length
* values if specified.
*
* @throws SqlException If any exception occurs while
* re-creating the underlying streams.
*/
protected InputStream reCreateStream() throws SqlException {
InputStream is_ = null;
//Verify if a subset of the underlying
//LOB data was requested.
if(length != -1) {
//The length information is available.
//It should be used while re-creating
//the stream.
is_ = new BlobLocatorInputStream(con, blob, currentPos,
length - currentPos +1);
}
else {
//The length information is not
//available.
is_ = new BlobLocatorInputStream(con, blob, currentPos, -1);
}
return is_;
}
}
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