How to change log4j log levels at runtime?

Here is the source code for log4jAdmin.jsp. I have copied under root of my WAR. Once you deployed the WAR, you can change the log levels on the fly without bouncing the servers. Remember you should have configured log4j in your applications properly. Please follow this link if you have any trouble in configuring log4j.
Once you copy this log4jAdmin.jsp under root of your web app, you can access it by entering
http://host_name:port/webapp/log4jAdmin.jsp

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:&nbsp;&nbsp;
        <input name="logNameFilter" type="text" size="50" value="<%=(logNameFilter == null ? "":logNameFilter)%>"

               class="filterText"/>
        <input name="logNameFilterType" type="submit" value="<%=beginsWithFilter%>" class="filterButton"/>&nbsp;

        <input name="logNameFilterType" type="submit" value="<%=containsFilter%>" class="filterButton"/>&nbsp;

        <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 : "") + "&logNameFilterType=" + (logNameFilterType != null ? logNameFilterType : "");

                    if (logger.getLevel() == Level.toLevel(logLevels[cnt]) || logger.getEffectiveLevel() == Level.toLevel(logLevels[cnt])) {

            %>
            [<%=logLevels[cnt].toUpperCase()%>]

            <%
            } else {
            %>
            <a href='<%=url%>'>[<%=logLevels[cnt]%>]</a>&nbsp;

            <%
                    }
                }
            %>
        </td>
    </tr>

    <%
        }
    %>
</table>
<h2>
    Revision: 1.0<br/>
    Page Load Time (Millis): <%=(System.currentTimeMillis() - beginPageLoadTime)%>
</h2>
</div>
</body>
</html>

10 comments:

  1. I have tried it.
    In fact modification didn't take place.

    I'm using an Log4j XML configuration.

    ReplyDelete
  2. This worked for me, although I needed to add 1 more level TRACE to the array.

    ReplyDelete
  3. This worked for me too, but it doesn't show every classes! I couldn't find the reason because only some classes are shown

    ReplyDelete
  4. hi,
    This worked for me too. but i am getting all the loggers(loggers from frameworks as well). i want to get only my application loggers. how can i do that.

    ReplyDelete
  5. Hello,

    very convenient and useful JSP! Thank you!

    Are there any licensing terms?
    I would like to include it into our GNU GPL v2 licensed product, of course, with a link back to this page.

    Thank you in advance!

    ReplyDelete
  6. I created a new java application module (jar) to do this in a web interface, and also view the log.
    To configure the jar, must be placed in the WEB-INF/lib folder, and add a mapping to the servlet in the WEB-INF/web.xml file.
    Look my site! http://www.log4jwebtracker.com

    ReplyDelete
  7. Hi,
    Nice article. I have question.Say I have application A.ear which has a web application A.war. I have included the log4jAdmin.jsp in this war to control the logging levels dynamically at runtime for loggers used in this application. I also have deployed another appication B.ear in weblogic in the same server instance. This application too has its share of loggers defined in it's own log4j.xml file. How do I make the loggers of application B.ear visible in log4jAdmin.jsp page which is part of A.ear. I am using weblogic 9.2.

    I know that according to classloader concepts, each application has its own classloader & your solution of moving log4j related files(jar and xml) to a common domain folder would have probably worked but for reasons beyond my control I cannot do this as A.ear which is a propietory application from Oracle(belongs to one of their Communication Suite of products) breaks down if I follow your suggestion. B.ear is a custom applcation developed by me which contains plugins which are nothing but Enterprise beans invoked by A.ear.

    So is there a way I can make loggers visible across all deployed applications so that using just one log4jAdmin.jsp I can change their logging levels? I know what I am trying to achiebce works because the latest version of A.ear which was released by Oracle for WL 10.3.3, the loggers defined for B.ear were visible in log4jAdmin.jsp page of A.ear. I am wondering what needs to be done so that I acheive same results with WL 9.2.

    ReplyDelete
  8. It works! Only a question, how it will behave on a clustered environment?

    ReplyDelete
  9. Looks like copied from http://nelz.net/2008/04/08/log4j-runtime-configuration/

    ReplyDelete