Apache Tomcat 6.0.43

org.apache.catalina.ha.deploy
Class FileMessageFactory

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

public class FileMessageFactory
extends java.lang.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  java.io.File file
          The file that we are reading/writing
protected  java.io.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  java.util.concurrent.atomic.AtomicLong lastMessageProcessed
          The number of the last message procssed.
static Log log
           
protected  java.util.Map<java.lang.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  java.io.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
 java.io.File getFile()
           
static FileMessageFactory getInstance(java.io.File f, boolean openForWrite)
          Creates a factory to read or write from a file.
static void main(java.lang.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

log

public static Log log

READ_SIZE

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

See Also:
Constant Field Values

file

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


out

protected java.io.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 java.util.concurrent.atomic.AtomicLong lastMessageProcessed
The number of the last message procssed. Message IDs are 1 based.


msgBuffer

protected java.util.Map<java.lang.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(java.io.File f,
                                             boolean openForWrite)
                                      throws java.io.FileNotFoundException,
                                             java.io.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:
java.io.FileNotFoundException - - if the file to be read doesn't exist
java.io.IOException - - if it fails to create the file that is to be written

readMessage

public FileMessage readMessage(FileMessage f)
                        throws java.lang.IllegalArgumentException,
                               java.io.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:
java.lang.IllegalArgumentException - - if the factory is for writing or is closed
java.io.IOException - - if a file read exception occurs

writeMessage

public boolean writeMessage(FileMessage msg)
                     throws java.lang.IllegalArgumentException,
                            java.io.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:
java.lang.IllegalArgumentException - - if the factory is opened for read or closed
java.io.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 java.lang.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:
java.lang.IllegalArgumentException

main

public static void main(java.lang.String[] args)
                 throws java.lang.Exception
Example usage.

Parameters:
args - String[], args[0] - read from filename, args[1] write to filename
Throws:
java.lang.Exception

getFile

public java.io.File getFile()

Apache Tomcat 6.0.43

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