org.qbroker.jms

Class MessagePacket

java.lang.Object

org.qbroker.jms.MessagePacket

public class MessagePacket
extends java.lang.Object

MessagePacket handles JMS Messages IO on DatagramSocket. The DatagramSocket has to be established before using this object.

There are four methods, listen(), talk(), inquire() and reply() on packets. The method of listen() is NOT MT-Safe. The method of talk() is for asynchronous output whereas inquire() is for synchronous requests.

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
MessagePacket(java.util.Map props)

Method Summary

Modifier and Type	Method and Description
java.lang.String	getOperation()
long	inquire(XQueue xq, java.net.DatagramSocket sock) It listens to an XQueue for JMS Messages and converts the content of the message into a packet as a request.
long	listen(java.net.DatagramSocket in, XQueue xq) It listens to the DatagramSocket for incoming DatagramPackets.
long	reply(java.net.DatagramSocket sock, XQueue xq) It listens to a DatagramSocket for incoming DatagramPackets and converts the packet into a JMS message as a request.
long	talk(XQueue xq, java.net.DatagramSocket out) It continually gets a JMS Message from the XQueue, loads its content to a DatagramPacket according to the format rules and sends the packet to the DatagramSocket.

Methods inherited from class java.lang.Object

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

Constructor Detail

MessagePacket

public MessagePacket(java.util.Map props)

Method Detail

listen

public long listen(java.net.DatagramSocket in,
                   XQueue xq)
            throws java.io.IOException,
                   javax.jms.JMSException

It listens to the DatagramSocket for incoming DatagramPackets. Once receiving a DatagramPacket, it loads the payload of the packet to a JMSMessage and puts it to the XQueue as output.

Most of the IOExceptions from the stream IO operations, like receive, will be thrown to notify the caller. The caller is supposed to catch the exception, either to reset the socket or to do other stuff. It also throws JMSException from the operations regarding to the message itself, like get/set JMS properties. This does not require to reset the socket at all.

This method is NOT MT-Safe.

Throws:

java.io.IOException

javax.jms.JMSException

reply

public long reply(java.net.DatagramSocket sock,
                  XQueue xq)
           throws java.io.IOException,
                  javax.jms.JMSException

It listens to a DatagramSocket for incoming DatagramPackets and converts the packet into a JMS message as a request. Once receiving a DatagramPacket, it loads the payload of the packet to a JMSMessage and puts it to the XQueue as output. Meanwhile, it checks the XQueue for the feedback messages. Once it finds one, the content of the message will be sent out as the reply.

Most of the IOExceptions from the packet IO operations, like receive, will be thrown to notify the caller. The caller is supposed to catch the exception, either to reset the socket or to do other stuff. It also throws JMSException from the operations regarding to the message itself, like get/set JMS properties. This does not require to reset the socket at all.

This method is NOT MT-Safe.

Throws:

java.io.IOException

javax.jms.JMSException

inquire

public long inquire(XQueue xq,
                    java.net.DatagramSocket sock)
             throws java.io.IOException,
                    javax.jms.JMSException

It listens to an XQueue for JMS Messages and converts the content of the message into a packet as a request. Once receiving a message, it loads its content to a DatagramPacket according to the format rules and sends the packet to the DatagramSocket. Meanwhile, it listens to the DatagramSocket for reply packet and sends the reply back to the XQueue if there is one.

Most of the IOExceptions from the packet IO operations, like send, will be thrown to notify the caller. The caller is supposed to catch the exception, either to reset the socket or to do other stuff. It also throws JMSException from the operations regarding to the message itself, like get/set JMS properties. This does not require to reset the socket at all.

Since the inquire 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 inquirey is successful. This method will not acknowledge messages. It is up to the requester to do that.

This method is NOT MT-Safe.

Throws:

java.io.IOException

javax.jms.JMSException

talk

public long talk(XQueue xq,
                 java.net.DatagramSocket out)
          throws java.io.IOException,
                 javax.jms.JMSException

It continually gets a JMS Message from the XQueue, loads its content to a DatagramPacket according to the format rules and sends the packet to the DatagramSocket.

Most of the IOExceptions from the packet IO operations, like send, will be thrown to notify the caller. The caller is supposed to catch the exception, either to reset the socket or to do other stuff. It also throws JMSException from the operations regarding to the message itself, like get/set JMS properties. This does not require to reset the socket at all.

It will not modify the original messages. If the XQueue has enabled the EXTERNAL_XA, it will also acknowledge every messages. This method is MT-Safe.

Throws:

java.io.IOException

javax.jms.JMSException

getOperation

public java.lang.String getOperation()