Nelz' Blog
Ruminations on Development
Tuesday Apr 08, 2008
Log4J Runtime Configuration
Ok... I know that in past projects, my teams have been able to put together a JSP to modify Log4J
configuration at runtime. However, doing a google search really only found a couple of descriptions of HOW to do it, but I wanted a more cut & paste solution.
So, after finding one in some code, I thought I would re-post it here. I give you "log4jAdmin.jsp":
<%@ page language="java" contentType="text/html;charset=UTF-8"%>
<%@ page import="org.apache.log4j.Level"%>
<%@ page import="org.apache.log4j.LogManager"%>
<%@ page import="org.apache.log4j.Logger"%>
<%@ page import="java.util.HashMap"%>
<%@ page import="java.util.Enumeration"%>
<%@ page import="java.util.Set"%>
<%@ page import="java.util.Arrays"%>
<% long beginPageLoadTime = System.currentTimeMillis();%>
<html>
<head>
<title>Log4J Administration</title>
<style type="text/css">
<!--
#content { margin: 0px; padding: 0px; text-align: center; background-color: #ccc; border: 1px solid #000; width: 100%;}
body { position: relative; margin: 10px; padding 0px; color: #333; }
h1 { margin-top: 20px; font: 1.5em Verdana, Arial, Helvetica sans-serif;}
h2 { margin-top: 10px; font: 0.75em Verdana, Arial, Helvetica sans-serif; text-align: left; }
a, a:link, a:visited, a:active { color: red; text-decoration: none; text-transform: uppercase; }
table { width: 100%; background-color: #000; padding: 3px; border: 0px;}
th { font-size: 0.75em; background-color: #ccc; color: #000; padding-left: 5px; text-align: center; border: 1px solid #ccc; white-space: nowrap; }
td { font-size: 0.75em; background-color: #fff; white-space: nowrap;}
td.center { font-size: 0.75em; background-color: #fff; text-align: center; white-space: nowrap;}
.filterForm { font-size: 0.9em; background-color: #000; color: #fff; padding-left: 5px; text-align: left; border: 1px solid #000; white-space: nowrap;}
.filterText { font-size: 0.75em; background-color: #fff; color: #000; text-align: left; border: 1px solid #ccc; white-space: nowrap;}
.filterButton { font-size: 0.75em; background-color: #000; color: #fff; padding-left: 5px; padding-right: 5px; text-align: center; border: 1px solid #ccc; width: 100px; white-space: nowrap;}
-->
</style>
</head>
<body onLoad="javascript:document.logFilterForm.logNameFilter.focus();">
<%
String containsFilter = "Contains";
String beginsWithFilter = "Begins With";
String[] logLevels = { "debug", "info", "warn", "error", "fatal", "off" };
String targetOperation = (String)request.getParameter("operation");
String targetLogger = (String)request.getParameter("logger");
String targetLogLevel = (String)request.getParameter("newLogLevel");
String logNameFilter = (String)request.getParameter("logNameFilter");
String logNameFilterType = (String)request.getParameter("logNameFilterType");
%>
<div id="content">
<h1>Log4J Administration</h1>
<div class="filterForm">
<form action="log4jAdmin.jsp" name="logFilterForm">Filter Loggers:
<input name="logNameFilter" type="text" size="50" value="<%=(logNameFilter == null ? "":logNameFilter)%>" class="filterText" />
<input name="logNameFilterType" type="submit" value="<%=beginsWithFilter%>" class="filterButton" />
<input name="logNameFilterType" type="submit" value="<%=containsFilter%>" class="filterButton" />
<input name="logNameClear" type="button" value="Clear" class="filterButton" onmousedown='javascript:document.logFilterForm.logNameFilter.value="";' />
<input name="logNameReset" type="reset" value="Reset" class="filterButton" />
<param name="operation" value="changeLogLevel" />
</form>
</div>
<table cellspacing="1">
<tr>
<th width="25%">Logger</th>
<th width="25%">Parent Logger</th>
<th width="15%">Effective Level</th>
<th width="35%">Change Log Level To</th>
</tr>
<%
Enumeration loggers = LogManager.getCurrentLoggers();
HashMap loggersMap = new HashMap(128);
Logger rootLogger = LogManager.getRootLogger();
if(!loggersMap.containsKey(rootLogger.getName()))
{
loggersMap.put(rootLogger.getName(), rootLogger);
}
while(loggers.hasMoreElements())
{
Logger logger = (Logger)loggers.nextElement();
if(logNameFilter == null || logNameFilter.trim().length() == 0)
{
loggersMap.put(logger.getName(), logger);
}
else if(containsFilter.equals(logNameFilterType))
{
if(logger.getName().toUpperCase().indexOf(logNameFilter.toUpperCase()) >= 0)
{
loggersMap.put(logger.getName(), logger);
}
}
else
{
// Either was no filter in IF, contains filter in ELSE IF, or begins with in ELSE
if(logger.getName().startsWith(logNameFilter))
{
loggersMap.put(logger.getName(), logger);
}
}
}
Set loggerKeys = loggersMap.keySet();
String[] keys = new String[loggerKeys.size()];
keys = (String[])loggerKeys.toArray(keys);
Arrays.sort(keys, String.CASE_INSENSITIVE_ORDER);
for(int i=0; i<keys.length; i++)
{
Logger logger = (Logger)loggersMap.get(keys[i]);
// MUST CHANGE THE LOG LEVEL ON LOGGER BEFORE GENERATING THE LINKS AND THE
// CURRENT LOG LEVEL OR DISABLED LINK WON'T MATCH THE NEWLY CHANGED VALUES
if("changeLogLevel".equals(targetOperation) && targetLogger.equals(logger.getName()))
{
Logger selectedLogger = (Logger)loggersMap.get(targetLogger);
selectedLogger.setLevel(Level.toLevel(targetLogLevel));
}
String loggerName = null;
String loggerEffectiveLevel = null;
String loggerParent = null;
if(logger != null)
{
loggerName = logger.getName();
loggerEffectiveLevel = String.valueOf(logger.getEffectiveLevel());
loggerParent = (logger.getParent() == null ? null : logger.getParent().getName());
}
%>
<tr>
<td><%=loggerName%></td>
<td><%=loggerParent%></td>
<td><%=loggerEffectiveLevel%></td>
<td class="center">
<%
for(int cnt=0; cnt<logLevels.length; cnt++)
{
String url = "/log4jAdmin.jsp?operation=changeLogLevel&logger=" + loggerName + "&newLogLevel=" + logLevels[cnt] + "&logNameFilter=" + (logNameFilter != null ? logNameFilter : "");
if(logger.getLevel() == Level.toLevel(logLevels[cnt]) || logger.getEffectiveLevel() == Level.toLevel(logLevels[cnt]))
{
%>
[<%=logLevels[cnt].toUpperCase()%>]
<%
}
else
{
%>
<a href='<%=url%>'>[<%=logLevels[cnt]%>]</a>
<%
}
}
%>
</td>
</tr>
<%
}
%>
</table>
<h2>
Revision: 1.0<br />
Page Load Time (Millis): <%=(System.currentTimeMillis() - beginPageLoadTime)%>
</h2>
</div>
</body>
</html>
If you've got a basic Log4J setup running, this should be a trivial add, allowing you to modify logging levels at runtime.
Here are a couple of caveats:
- You will need to have a base log4j.configuration file set up at startup. A log4j.properties file is fine for basic setups, but a log4j.xml file is reportedly more flexible and powerful.
- Standard JSP security is advised... You may need/want to hid this JSP behind whatever MVC framework you use... You DEFINITELY don't want this JSP exposed to just anyone hitting your server!
- Towards the bottom of this file, there's a hard-coded URL back to this page... If you change the name/url, make sure to update this... (I haven't looked to hard at it, but I assume there's a way to access the REQUEST object to find out the base URL for self reference.)
Good Luck!
Update (20008-04-10): Jon Mann pointed out that there are two hard-coded URLs in the JSP. I updated them both to be "log4jAdmin.jsp" on lines 51 and 140. Thanks Jon!
Posted at 01:25PM Apr 08, 2008 by Nelson "Nelz" Carpentier in Java | Comments[1]