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/*
 * 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.tomcat.util.http.fileupload;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;


/**
 * An output stream which will retain data in memory until a specified
 * threshold is reached, and only then commit it to disk. If the stream is
 * closed before the threshold is reached, the data will not be written to
 * disk at all.
 * 

* This class originated in FileUpload processing. In this use case, you do * not know in advance the size of the file being uploaded. If the file is small * you want to store it in memory (for speed), but if the file is large you want * to store it to file (to avoid memory issues). */ public class DeferredFileOutputStream extends ThresholdingOutputStream { // ----------------------------------------------------------- Data members /** * The output stream to which data will be written prior to the threshold * being reached. */ private ByteArrayOutputStream memoryOutputStream; /** * The output stream to which data will be written at any given time. This * will always be one of memoryOutputStream or * diskOutputStream. */ private OutputStream currentOutputStream; /** * The file to which output will be directed if the threshold is exceeded. */ private File outputFile; /** * The temporary file prefix. */ private final String prefix; /** * The temporary file suffix. */ private final String suffix; /** * The directory to use for temporary files. */ private final File directory; // ----------------------------------------------------------- Constructors /** * Constructs an instance of this class which will trigger an event at the * specified threshold, and save data to a file beyond that point. * The initial buffer size will default to 1024 bytes which is ByteArrayOutputStream's default buffer size. * * @param threshold The number of bytes at which to trigger an event. * @param outputFile The file to which data is saved beyond the threshold. */ public DeferredFileOutputStream(final int threshold, final File outputFile) { this(threshold, outputFile, null, null, null, ByteArrayOutputStream.DEFAULT_SIZE); } /** * Constructs an instance of this class which will trigger an event at the * specified threshold, and save data either to a file beyond that point. * * @param threshold The number of bytes at which to trigger an event. * @param outputFile The file to which data is saved beyond the threshold. * @param prefix Prefix to use for the temporary file. * @param suffix Suffix to use for the temporary file. * @param directory Temporary file directory. * @param initialBufferSize The initial size of the in memory buffer. */ private DeferredFileOutputStream(final int threshold, final File outputFile, final String prefix, final String suffix, final File directory, final int initialBufferSize) { super(threshold); this.outputFile = outputFile; this.prefix = prefix; this.suffix = suffix; this.directory = directory; memoryOutputStream = new ByteArrayOutputStream(initialBufferSize); currentOutputStream = memoryOutputStream; } // --------------------------------------- ThresholdingOutputStream methods /** * Returns the current output stream. This may be memory based or disk * based, depending on the current state with respect to the threshold. * * @return The underlying output stream. * * @throws IOException if an error occurs. */ @Override protected OutputStream getStream() throws IOException { return currentOutputStream; } /** * Switches the underlying output stream from a memory based stream to one * that is backed by disk. This is the point at which we realise that too * much data is being written to keep in memory, so we elect to switch to * disk-based storage. * * @throws IOException if an error occurs. */ @Override protected void thresholdReached() throws IOException { if (prefix != null) { outputFile = File.createTempFile(prefix, suffix, directory); } FileUtils.forceMkdirParent(outputFile); final FileOutputStream fos = new FileOutputStream(outputFile); try { memoryOutputStream.writeTo(fos); } catch (final IOException e){ fos.close(); throw e; } currentOutputStream = fos; memoryOutputStream = null; } // --------------------------------------------------------- Public methods /** * Determines whether or not the data for this output stream has been * retained in memory. * * @return {@code true} if the data is available in memory; * {@code false} otherwise. */ public boolean isInMemory() { return !isThresholdExceeded(); } /** * Returns the data for this output stream as an array of bytes, assuming * that the data has been retained in memory. If the data was written to * disk, this method returns {@code null}. * * @return The data for this output stream, or {@code null} if no such * data is available. */ public byte[] getData() { if (memoryOutputStream != null) { return memoryOutputStream.toByteArray(); } return null; } /** * Returns either the output file specified in the constructor or * the temporary file created or null. *

* If the constructor specifying the file is used then it returns that * same output file, even when threshold has not been reached. *

* If constructor specifying a temporary file prefix/suffix is used * then the temporary file created once the threshold is reached is returned * If the threshold was not reached then {@code null} is returned. * * @return The file for this output stream, or {@code null} if no such * file exists. */ public File getFile() { return outputFile; } /** * Closes underlying output stream, and mark this as closed * * @throws IOException if an error occurs. */ @Override public void close() throws IOException { super.close(); } }





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