org.qbroker.jms

Class NNTPMessenger

java.lang.Object

org.qbroker.net.NNTPConnector

org.qbroker.jms.NNTPMessenger

All Implemented Interfaces:

Connector

public class NNTPMessenger
extends NNTPConnector

NNTPMessenger connects to an NNTP server and initializes one of the operations, such as fetch, retrieve and post. It carries out the operation with JMS Messages.

There are three methods, fetch(), retrieve(), list() and post(). The first method, fetch(), is used to fetch new articles from NNTP servers. The method of retrieve() is used for synchronous requests. The method of post() is used for asynchronous posting content to the NNTP server.

This is NOT MT-Safe. Therefore, you need to use multiple instances to achieve your MT goal.

Author:

yannanlu@yahoo.com

Field Summary

Fields inherited from class org.qbroker.net.NNTPConnector

ARTICLE_ALL, ARTICLE_BODY, ARTICLE_HEADER, hostname, isConnected, maxArticle, password, port, timeout, uri, username

Constructor Summary

Constructors

Constructor and Description
NNTPMessenger(java.util.Map props) Creates new NNTPMessenger

Method Summary

Modifier and Type	Method and Description
void	fetch(XQueue xq) It fetches new articles of a news group from the NNTP server and puts them to the XQ.
java.lang.String	getOperation()
void	list(XQueue xq) It gets a JMS message from xq that contains a newsgroup name for listing articles in it and gets the list via nntp.
void	post(XQueue xq) It gets a JMS Message from the XQueue and posts its content into the NNTP server continuously.
void	retrieve(XQueue xq) It gets a JMS message from xq that contains the information about an article to be retrieved and retrieves the article via nntp.

Methods inherited from class org.qbroker.net.NNTPConnector

close, connect, getArticleInfo, getArticleInfo, getArticleInfo, getDate, getNNTPClient, getReplyString, getURI, isAllowedToPost, isConnected, main, nntpGet, nntpGet, nntpListArticles, nntpListGroups, nntpPost, nntpPost, reconnect, setNewsgroup

Methods inherited from class java.lang.Object

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

Constructor Detail

NNTPMessenger

public NNTPMessenger(java.util.Map props)
              throws java.io.IOException

Creates new NNTPMessenger

Throws:

java.io.IOException

Method Detail

fetch

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

It fetches new articles of a news group from the NNTP server and puts them to the XQ. It is NOT reentry safe.

Throws:

java.io.IOException

javax.jms.JMSException

retrieve

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

It gets a JMS message from xq that contains the information about an article to be retrieved and retrieves the article via nntp. It puts the header info into the message header and puts the content of the article into the message body and sends it back. The requester at the other end of the XQueue can easily read the content out of the message.

Since the retrieve 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 retrieve is successful. Otherwise, the message body will not contain the content out of retrieve operation.

If the MaxIdleTime is set to none-zero, it will monitor the idle time and will throw TimeoutException once the idle time exceeds MaxIdleTime. it is up to the caller to handle this exception.

Throws:

java.io.IOException

TimeoutException

javax.jms.JMSException

list

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

It gets a JMS message from xq that contains a newsgroup name for listing articles in it and gets the list via nntp. It puts the list of articles into the message body one articleID per line and sends it back. The requester at the other end of the XQueue can easily read the list out of the message.

Since the list 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 list is successful. Otherwise, the message body will not contain the content out of the list operation.

If the MaxIdleTime is set to none-zero, it will monitor the idle time and will throw TimeoutException once the idle time exceeds MaxIdleTime. it is up to the caller to handle this exception.

Throws:

java.io.IOException

TimeoutException

javax.jms.JMSException

post

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

It gets a JMS Message from the XQueue and posts its content into the NNTP server continuously.

It will always try to retrieve the header info from the message based on HeaderField property. If the message does not contain the header info, the method will use the default header.

The post operation also supports the 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 MaxIdleTime is set to none-zero, it will monitor the idle time and will throw TimeoutException once the idle time exceeds MaxIdleTime. it is up to the caller to handle this exception.

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

Throws:

java.io.IOException

TimeoutException

javax.jms.JMSException

getOperation

public java.lang.String getOperation()