For information.
>Delivered-To: [EMAIL PROTECTED]
>From: Mark Womack <[EMAIL PROTECTED]>
>To: 'Ceki Gülcü' <[EMAIL PROTECTED]>
>Subject: RE: New Watchdog
>Date: Mon, 7 Jan 2002 11:48:50 -0800
>X-Mailer: Internet Mail Service (5.5.2655.55)
>
>Ceki,
>
>Enclosed is an HTTPWatcher class which watches a URL, and when the
>last-modified header changes, the url as a source for the reconfiguration
>data. I wrote it last night.
>
>One other point that I did not make very strongly in my last email, is that
>with the new Watchdog class, the developer can specify the type of Watchdog
>they want to use instead of only relying on what is provided by the
>configurator class. Right now, Property and DOM configurator
>configureAndWatch() methods require a file for the FileWatchdog. But, now
>we can just as easily support different watchdog types simply by creating
>the watchdog, giving it the configurator class to use, and then starting it.
>I don't know if you really need any configuration methods on the
>configurators at all and would never need to add a method to support a
>specific type of Watchdog.
>
>hope to hear from you,
>-Mark
>
>-----Original Message-----
>From: Mark Womack
>Sent: Sunday, January 06, 2002 4:08 PM
>To: 'Ceki Gülcü'
>Subject: New Watchdog
>
>
>Ceki,
>
>Way back, I submitted an updated version of the Watchdog class. The idea
>being that I felt it needed some work in order to support other kinds of
>watchdogs. That and there was the suggestion that Watchdogs be creatable
>via the configuration file (which in retrospect I'm not sure was a good
>idea).
>
>Anyway, enclosed is another stab at the Watchdog class. I reworked my
>original idea over the holidays, and I think this version is much better.
>Please review and consider it for inclusion in a future version of Log4J.
>Even if you think it is crap, I would like to hear back from you so I learn
>from it. I also included an updated DOMConfigurator.java that uses the
>updated FileWatchdog class.
>
>- The Watchdog class is now more configuration oriented, having a
>reconfigure() method. Since watchdogs are currently only used for
>reconfiguration, I thought this was ok, but I could rework the class to move
>the configuration specific code into a ConfigurationWatchdog subclass.
>- Watchdogs can be very standalone. Just give them a configurator class,
>and they can handle the rest. The only requirement is that the configurator
>has to support a version of the doConfigure() method that supports an
>InputStream. If this method was moved into the Configurator interface, then
>I would not need to use reflection to find the method; I could assume it was
>there.
>- Watchdogs can be started, stopped, re-started. They implement the
>Runnable interface instead of extending Thread directly. And the Watchdog
>class maintains a static list of active Watchdogs. This makes it fairly
>easy to stop all of the active watchdogs from one location.
>- The base Watchdog class makes absolutely no assumptions of what entity is
>being watched (file, etc) and no assumptions that the configuration settings
>are directly connected to the watched entity (ie. you could write a watchdog
>that watches file A but then grabs the configuration information from a file
>B). It only needs the configuration settings to be provided as an
>InputStream.
>
>My goal is still to write an HTTPWatchdog class to watch a given url and
>reconfigure is the Last-Modified field in the response header is greater
>than the one the watchdog has. I am going to work on that tonight and this
>next week.
>
>Again, I would appreciate your comments.
>
>Thanks for your time,
>-Mark
>
--
Ceki Gülcü - http://qos.ch
/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE file.
*/
// Contributors: Mark Womack
package org.apache.log4j.helpers;
import java.io.InputStream;
import java.io.File;
import java.io.FileInputStream;
import java.net.URL;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
/**
Return the modification time for a http url, and when asked, return an
InputStream to the url contents.
*/
public class HTTPWatchdog extends Watchdog {
/**
The url to observe for changes.
*/
protected URL url;
protected String urlPath;
private boolean warnedAlready = false;
public
HTTPWatchdog() { }
public
HTTPWatchdog(URL _url) {
url = _url;
}
public
HTTPWatchdog(String _urlPath) {
urlPath = _urlPath;
}
public
void setUrl(String _urlPath) {
urlPath = _urlPath;
}
public
void setUrl(URL _url) {
url = _url;
}
public
String getUrl() {
if (url != null)
return url.getPath();
else
return urlPath;
}
protected
long getModificationTime() {
long retModTime = 0;
// make sure we have a url
if (url == null) {
try {
url = new URL(urlPath);
} catch (MalformedURLException e) {
LogLog.warn("invalid url, url :["+urlPath+"].");
this.stopWatching();
return 0;
}
}
try {
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
// request just the headers
connection.setRequestMethod("HEAD");
connection.connect();
if (connection.getResponseCode() == 200) {
// get the last modified date and return it
retModTime = connection.getLastModified();
warnedAlready = false;
}
else {
if (!warnedAlready) {
LogLog.warn("error accessing url, response code " +
connection.getResponseCode());
warnedAlready = true;
}
}
} catch (Exception e) {
if (!warnedAlready) {
LogLog.warn("error accessing url: " + e.getMessage());
warnedAlready = true;
}
}
return retModTime;
}
protected
InputStream getConfigurationStream() {
try {
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
// request url contents
connection.connect();
// read past the header
// TODO
// return an InputStream to the contents
return connection.getInputStream();
} catch (Exception e) {
LogLog.warn("error accessing url: " + e.getMessage());
return null;
}
}
}
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