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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 static org.jboss.web.FileUploadMessages.MESSAGES;
 
 import java.io.File;
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).

Author(s):
Martin Cooper
gaxzerow
Version:
$Id: DeferredFileOutputStream.java 1281 2009-11-20 23:18:44Z remy.maucherat@jboss.com $
 
     extends ThresholdingOutputStream
 {
 
     // ----------------------------------------------------------- Data members
 

    
The output stream to which data will be written prior to the theshold 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 String prefix;

    
The temporary file suffix.
 
     private String suffix;

    
The directory to use for temporary files.
 
     private File directory;

    
    
True when close() has been called successfully.
 
     private boolean closed = false;
 
     // ----------------------------------------------------------- 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.

Parameters:
threshold The number of bytes at which to trigger an event.
outputFile The file to which data is saved beyond the threshold.
    public DeferredFileOutputStream(int thresholdFile outputFile)
    {
        super(threshold);
        this. = outputFile;
         = new ByteArrayOutputStream();
    }


    
Constructs an instance of this class which will trigger an event at the specified threshold, and save data to a temporary file beyond that point.

Parameters:
threshold The number of bytes at which to trigger an event.
prefix Prefix to use for the temporary file.
suffix Suffix to use for the temporary file.
directory Temporary file directory.
Since:
Commons IO 1.4
    public DeferredFileOutputStream(int thresholdString prefixString suffixFile directory)
    {
        this(threshold, (File)null);
        if (prefix == null) {
            throw .missingTemporaryFilePrefix();
        }
        this. = prefix;
        this. = suffix;
        this. = directory;
    }
    // --------------------------------------- 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.

Returns:
The underlying output stream.
Throws:
java.io.IOException if an error occurs.
    @Override
    protected OutputStream getStream() throws IOException
    {
        return ;
    }


    
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:
java.io.IOException if an error occurs.
    @Override
    protected void thresholdReached() throws IOException
    {
        if ( != null) {
             = File.createTempFile();
        }
        FileOutputStream fos = new FileOutputStream();
        .writeTo(fos);
         = fos;
         = null;
    }
    // --------------------------------------------------------- Public methods


    
Determines whether or not the data for this output stream has been retained in memory.

Returns:
true if the data is available in memory; 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 null.

Returns:
The data for this output stream, or null if no such data is available.
    public byte[] getData()
    {
        if ( != null)
        {
            return .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 threashold has not been reached.

If constructor specifying a temporary file prefix/suffix is used then the temporary file created once the threashold is reached is returned If the threshold was not reached then null is returned.

Returns:
The file for this output stream, or null if no such file exists.
    public File getFile()
    {
        return ;
    }
    
        
    
Closes underlying output stream, and mark this as closed

Throws:
java.io.IOException if an error occurs.
    @Override
    public void close() throws IOException
    {
        super.close();
         = true;
    }
    
    
    
Writes the data from this output stream to the specified output stream, after it has been closed.

Parameters:
out output stream to write to.
Throws:
java.io.IOException if this stream is not yet closed or an error occurs.
    public void writeTo(OutputStream outthrows IOException 
    {
        // we may only need to check if this is closed if we are working with a file
        // but we should force the habit of closing wether we are working with
        // a file or memory.
        if (!)
        {
            throw new IOException(.streamNotClosed());
        }
        
        if(isInMemory())
        {
            .writeTo(out);
        }
        else
        {
            FileInputStream fis = new FileInputStream();
            try {
                IOUtils.copy(fisout);
            } finally {
                IOUtils.closeQuietly(fis);
            }
        }
    }
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