org.qbroker.jms

Class MessageLogger

java.lang.Object

org.qbroker.jms.MessageLogger

public class MessageLogger
extends java.lang.Object

MessageLogger handles common logs as JMS Messages.

There are three methods, fetch(), download() and append(). The former is NOT MT-Safe. During the fetch operation, the message acknowledgement and session transaction are supported via explicitly persisting reference. The method of download() is used for synchronous requests. The method of append() is used for asynchronous logging or storing.

For fetch(), there are 4 different transaction mode determined by XAMode. For XAMode = 1 or 3, the client based transcation is enabled so that the commit is done by the persister when it completes to persist the message. If XAMode = 2, the session commit is enabled so that the commit will be done when the read operation finishes and the log file is closed. The session can be forced to termination if MaxNumberMessage is larger than 0 and the total number of processed logs and dropped logs exceeds it. For XAMode = 0, the auto commit is enabled. In this case, the persistence of the state info is determined by SaveReference. By default, SaveReference is set to be true. It means the state info will be flushed to the disk on every processed log entry. If SaveReference is set to false, otherwise, the state info will not saved to the reference file.

For charSet and encoding, you can overwrite the default encoding by starting JVM with "-Dfile.encoding=UTF8 your_class".

Author:

yannanlu@yahoo.com

Constructor Summary

Constructors

Constructor and Description
MessageLogger(java.util.Map props)

Method Summary

Modifier and Type	Method and Description
void	acknowledge(long[] state)
void	append(XQueue xq) It gets a JMS Message from an XQueue and append the formatted content to the logfile continuously, or store the content to a file.
void	commit()
void	download(XQueue xq) It gets a JMS message from xq that contains a filename to be downloaded and downloads the local file.
void	fetch(XQueue xq) It fetches new log entries from the logfile and packages them into JMS Messages and add the messages to an XQueue.
java.lang.String	getOperation()
void	rollback()

Methods inherited from class java.lang.Object

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

Constructor Detail

MessageLogger

public MessageLogger(java.util.Map props)

Method Detail

fetch

public void fetch(XQueue xq)
           throws java.io.IOException,
                  javax.jms.JMSException

It fetches new log entries from the logfile and packages them into JMS Messages and add the messages to an XQueue. It has the acknowledge support or session transcation support if the XAMode is enabled. With the session transaction, the application has to call commit() explicitly to persist the reference.

For those nohit log entries, it will commit them anyway. This may break the client transaction control. So please make sure to use the correct pattern to catch all entries.

This method is NOT MT-Safe.

Throws:

java.io.IOException

javax.jms.JMSException

download

public void download(XQueue xq)
              throws java.io.IOException,
                     javax.jms.JMSException

It gets a JMS message from xq that contains a filename to be downloaded and downloads the local file. It puts the content of the file into the message body and sends it back. The requester at the other end of the xq can easily read the content out of the message.

Since the download operation relies on a request, this method will intercept the request and process it. The incoming message is required to be writeable. The method will set a String property of the message specified by the RCField with the return code, indicating the status of the process to fulfill the request. The requester is required to check the value of the property once it gets the message back. If the return code is 0, the download is successful. Otherwise, the message body will not contain the content out of download operation.

This method will not acknowledge messages. It is up to the requester to do that.

Throws:

java.io.IOException

javax.jms.JMSException

append

public void append(XQueue xq)
            throws java.io.IOException,
                   javax.jms.JMSException

It gets a JMS Message from an XQueue and append the formatted content to the logfile continuously, or store the content to a file.

The store or append operation also supports requests. If the XAMode has enabled the XA_CLIENT bit, it will treat the message as a request from the uplink. In this case, the incoming message is required to be writeable. The method will set a String property of the message specified by the RCField with the return code, indicating the status of the process to fulfill the request. The requester is supposed to check the value of the property once it gets the message back. If the return code is 0, the operation is successful. Otherwise, the request will be dropped due to failures. On the other hand, if the XA_CLIENT bit has been disabled by XAMode, the incoming message will not be modified.

If the XQueue has enabled the EXTERNAL_XA, it will also acknowledge the messages. This method is MT-Safe.

Throws:

java.io.IOException

javax.jms.JMSException

rollback

public void rollback()
              throws javax.jms.JMSException

Throws:

javax.jms.JMSException

commit

public void commit()
            throws javax.jms.JMSException

Throws:

javax.jms.JMSException

acknowledge

public void acknowledge(long[] state)
                 throws javax.jms.JMSException

Throws:

javax.jms.JMSException

getOperation

public java.lang.String getOperation()