org.apache.catalina.ha.deploy
Class FileMessageFactory

java.lang.Object
  org.apache.catalina.ha.deploy.FileMessageFactory

public class FileMessageFactory
extends Object

This factory is used to read files and write files by splitting them up into smaller messages. So that entire files don't have to be read into memory.
The factory can be used as a reader or writer but not both at the same time. When done reading or writing the factory will close the input or output streams and mark the factory as closed. It is not possible to use it after that.
To force a cleanup, call cleanup() from the calling object.
This class is not thread safe.

Version:

1.0

Author:

Filip Hanik

Field Summary

protected boolean	closed Once the factory is used, it can not be reused.
protected byte[]	data The bytes that we hold the data in, not thread safe.
protected File	file The file that we are reading/writing
protected FileInputStream	in When openForWrite=false, the input stream is held by this variable
protected boolean	isWriting Flag that indicates if a thread is writing messages to disk.
protected AtomicLong	lastMessageProcessed The number of the last message processed.
protected Map<Long,FileMessage>	msgBuffer Messages received out of order are held in the buffer until required.
protected int	nrOfMessagesProcessed The number of messages we have written
protected boolean	openForWrite True means that we are writing with this factory.
protected FileOutputStream	out When openForWrite=true, the output stream is held by this variable
static int	READ_SIZE The number of bytes that we read from file
protected long	size The total size of the file
protected long	totalNrOfMessages The total number of packets that we split this file into

Method Summary

protected void	checkState(boolean openForWrite) Check to make sure the factory is able to perform the function it is asked to do.
void	cleanup() Closes the factory, its streams and sets all its references to null
File	getFile()
static FileMessageFactory	getInstance(File f, boolean openForWrite) Creates a factory to read or write from a file.
static void	main(String[] args) Example usage.
FileMessage	readMessage(FileMessage f) Reads file data into the file message and sets the size, totalLength, totalNrOfMsgs and the message number If EOF is reached, the factory returns null, and closes itself, otherwise the same message is returned as was passed in.
boolean	writeMessage(FileMessage msg) Writes a message to file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

READ_SIZE

public static final int READ_SIZE

The number of bytes that we read from file

See Also:

Constant Field Values

file

protected File file

The file that we are reading/writing

openForWrite

protected boolean openForWrite

True means that we are writing with this factory. False means that we are reading with this factory

closed

protected boolean closed

Once the factory is used, it can not be reused.

in

protected FileInputStream in

When openForWrite=false, the input stream is held by this variable

out

protected FileOutputStream out

When openForWrite=true, the output stream is held by this variable

nrOfMessagesProcessed

protected int nrOfMessagesProcessed

The number of messages we have written

size

protected long size

The total size of the file

totalNrOfMessages

protected long totalNrOfMessages

The total number of packets that we split this file into

lastMessageProcessed

protected AtomicLong lastMessageProcessed

The number of the last message processed. Message IDs are 1 based.

msgBuffer

protected Map<Long,FileMessage> msgBuffer

Messages received out of order are held in the buffer until required. If everything is worked as expected, messages will spend very little time in the buffer.

data

protected byte[] data

The bytes that we hold the data in, not thread safe.

isWriting

protected boolean isWriting

Flag that indicates if a thread is writing messages to disk. Access to this flag must be synchronised.

Method Detail

getInstance

public static FileMessageFactory getInstance(File f,
                                             boolean openForWrite)
                                      throws FileNotFoundException,
                                             IOException

Creates a factory to read or write from a file. When opening for read, the readMessage can be invoked, and when opening for write the writeMessage can be invoked.

Parameters:

f - File - the file to be read or written

openForWrite - boolean - true, means we are writing to the file, false means we are reading from it

Returns:

FileMessageFactory

Throws:

FileNotFoundException - - if the file to be read doesn't exist

IOException - - if it fails to create the file that is to be written

readMessage

public FileMessage readMessage(FileMessage f)
                        throws IllegalArgumentException,
                               IOException

Reads file data into the file message and sets the size, totalLength, totalNrOfMsgs and the message number
If EOF is reached, the factory returns null, and closes itself, otherwise the same message is returned as was passed in. This makes sure that not more memory is ever used. To remember, neither the file message or the factory are thread safe. dont hand off the message to one thread and read the same with another.

Parameters:

f - FileMessage - the message to be populated with file data

Returns:

FileMessage - returns the same message passed in as a parameter, or null if EOF

Throws:

IllegalArgumentException - - if the factory is for writing or is closed

IOException - - if a file read exception occurs

writeMessage

public boolean writeMessage(FileMessage msg)
                     throws IllegalArgumentException,
                            IOException

Writes a message to file. If (msg.getMessageNumber() == msg.getTotalNrOfMsgs()) the output stream will be closed after writing.

Parameters:

msg - FileMessage - message containing data to be written

Returns:

returns true if the file is complete and outputstream is closed, false otherwise.

Throws:

IllegalArgumentException - - if the factory is opened for read or closed

IOException - - if a file write error occurs

cleanup

public void cleanup()

Closes the factory, its streams and sets all its references to null

checkState

protected void checkState(boolean openForWrite)
                   throws IllegalArgumentException

Check to make sure the factory is able to perform the function it is asked to do. Invoked by readMessage/writeMessage before those methods proceed.

Parameters:

openForWrite - boolean

Throws:

IllegalArgumentException

main

public static void main(String[] args)
                 throws Exception

Example usage.

Parameters:

args - String[], args[0] - read from filename, args[1] write to filename

Throws:

Exception

getFile

public File getFile()