org.apache.catalina.ha.deploy

Class 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 booleanclosed
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 Filefile
The file that we are reading/writing
protected FileInputStreamin
When openForWrite=false, the input stream is held by this variable
protected booleanisWriting
Flag that indicates if a thread is writing messages to disk.
protected AtomicLonglastMessageProcessed
The number of the last message procssed.
static Loglog
protected Map<Long,FileMessage>msgBuffer
Messages received out of order are held in the buffer until required.
protected intnrOfMessagesProcessed
The number of messages we have written
protected booleanopenForWrite
True means that we are writing with this factory.
protected FileOutputStreamout
When openForWrite=true, the output stream is held by this variable
static intREAD_SIZE
The number of bytes that we read from file
protected longsize
The total size of the file
protected longtotalNrOfMessages
The total number of packets that we split this file into
Method Summary
protected voidcheckState(boolean openForWrite)
Check to make sure the factory is able to perform the function it is asked to do.
voidcleanup()
Closes the factory, its streams and sets all its references to null
FilegetFile()
static FileMessageFactorygetInstance(File f, boolean openForWrite)
Creates a factory to read or write from a file.
static voidmain(String[] args)
Example usage.
FileMessagereadMessage(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.
booleanwriteMessage(FileMessage msg)
Writes a message to file.

Field Detail

closed

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

data

protected byte[] data
The bytes that we hold the data in, not thread safe.

file

protected File file
The file that we are reading/writing

in

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

isWriting

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

lastMessageProcessed

protected AtomicLong lastMessageProcessed
The number of the last message procssed. Message IDs are 1 based.

log

public static Log log

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.

nrOfMessagesProcessed

protected int nrOfMessagesProcessed
The number of messages we have written

openForWrite

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

out

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

READ_SIZE

public static final int READ_SIZE
The number of bytes that we read from file

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

Method Detail

checkState

protected void checkState(boolean openForWrite)
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

cleanup

public void cleanup()
Closes the factory, its streams and sets all its references to null

getFile

public File getFile()

getInstance

public static FileMessageFactory getInstance(File f, boolean openForWrite)
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

main

public static void main(String[] args)
Example usage.

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

Throws: Exception

readMessage

public 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. 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)
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

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