org.jvnet.staxex.StreamingDataHandler Maven / Gradle / Ivy
Show all versions of webservices-rt Show documentation
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2010-2013 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* http://glassfish.java.net/public/CDDL+GPL_1_1.html
* or packager/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
package org.jvnet.staxex;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import java.io.BufferedInputStream;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
/**
* {@link DataHandler} extended to offer better buffer management
* in a streaming environment.
*
*
* {@link DataHandler} is used commonly as a data format across
* multiple systems (such as JAXB/WS.) Unfortunately, {@link DataHandler}
* has the semantics of "read as many times as you want", so this makes
* it difficult for involving parties to handle a BLOB in a streaming fashion.
*
*
* {@link StreamingDataHandler} solves this problem by offering methods
* that enable faster bulk "consume once" read operation.
*
* @author Jitendra Kotamraju
*/
public abstract class StreamingDataHandler extends DataHandler implements Closeable {
private String hrefCid;
public StreamingDataHandler(Object o, String s) {
super(o, s);
}
public StreamingDataHandler(URL url) {
super(url);
}
public StreamingDataHandler(DataSource dataSource) {
super(dataSource);
}
/**
* Works like {@link #getInputStream()} except that this method
* can be invoked only once.
*
*
* This is used as a signal from the caller that there will
* be no further {@link #getInputStream()} invocation nor
* {@link #readOnce()} invocation on this object (which would
* result in {@link IOException}.)
*
*
* When {@link DataHandler} is backed by a streaming BLOB
* (such as an attachment in a web service read from the network),
* this allows the callee to avoid unnecessary buffering.
*
*
* Note that it is legal to call {@link #getInputStream()}
* multiple times and then call {@link #readOnce()} afterward.
* Streams created such a way can be read in any order —
* there's no requirement that streams created earlier must be read
* first.
*
* @return
* always non-null. Represents the content of this BLOB.
* The returned stream is generally not buffered, so for
* better performance read in a big batch or wrap this into
* {@link BufferedInputStream}.
* @throws IOException
* if any i/o error
*/
public abstract InputStream readOnce() throws IOException;
/**
* Obtains the BLOB into a specified file.
*
*
* Semantically, this method is roughly equivalent to the following
* code, except that the actual implementation is likely to be a lot faster.
*
*
* InputStream i = getInputStream();
* OutputStream o = new FileOutputStream(dst);
* int ch;
* while((ch=i.read())!=-1) o.write(ch);
* i.close();
* o.close();
*
*
*
* The main motivation behind this method is that often
* {@link DataHandler} that reads data from a streaming source
* will use a temporary file as a data store to hold data
* (think of commons-fileupload.) In such case this method
* can be as fast as calling {@link File#renameTo(File)}.
*
*
* This method shouldn't be called when there are any
* open streams.
*
*
* After this method is invoked, {@link #readOnce()} and
* {@link #getInputStream()} will simply open the destination
* file you've specified as an argument. So if you further
* move the file or delete this file, those methods will
* behave in undefined fashion. For a simliar reason,
* calling this method multiple times will cause
* undefined behavior.
*/
public abstract void moveTo(File dst) throws IOException;
/**
* Releases any resources associated with this DataHandler.
* (such as an attachment in a web service read from a temp
* file will be deleted.) After calling this method, it is
* illegal to call any other methods.
*/
public abstract void close() throws IOException;
public String getHrefCid() {
return hrefCid;
}
public void setHrefCid(final String cid) {
this.hrefCid = cid;
}
}