src/site/xdoc/manual/eventlogging.xml - logging-log4j2 - Git at Google

 <?xml version="1.0"?>
 <!--
     Licensed to the Apache Software Foundation (ASF) under one or more
     contributor license agreements.  See the NOTICE file distributed with
     this work for additional information regarding copyright ownership.
     The ASF licenses this file to You under the Apache License, Version 2.0
     (the "License"); you may not use this file except in compliance with
     the License.  You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
 -->

 <document xmlns="http://maven.apache.org/XDOC/2.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
     <properties>
         <title>Log4j 2 API</title>
         <author email="rgoers@apache.org">Ralph Goers</author>
     </properties>

     <body>
         <section name="Log4j 2 API">
           <a name="EventLogging"/>
           <subsection name="Event Logging">
             <p>
               The EventLogger class provides a simple mechanism for logging events that occur in an application.
               While the EventLogger is useful as a way of initiating events that should be processed by an audit
               Logging system, by itself it does not implement any of the features an audit logging system would require
               such as guaranteed delivery.
             </p>
             <p>The recommended way of using the EventLogger in a typical web application is to populate
               the ThreadContext Map with data that is related to the entire lifespan of the request such as the user's
               id, the user's IP address, the product name, etc. This can easily be done in a servlet filter where
               the ThreadContext Map can also be cleared at the end of the request. When an event that needs to be
               recorded occurs a StructuredDataMessage should be created and populated.
               Then call EventLogger.logEvent(msg) where msg is a reference to the StructuredDataMessage.</p>

             <pre class="prettyprint linenums">
 import org.apache.logging.log4j.ThreadContext;
 import org.apache.commons.lang.time.DateUtils;

 import javax.servlet.Filter;
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.FilterChain;
 import javax.servlet.http.HttpSession;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.util.TimeZone;

 public class RequestFilter implements Filter {
     private FilterConfig filterConfig;
     private static String TZ_NAME = "timezoneOffset";

     public void init(FilterConfig filterConfig) throws ServletException {
         this.filterConfig = filterConfig;
     }

     /**
      * Sample filter that populates the MDC on every request.
      */
     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
             throws IOException, ServletException {
         HttpServletRequest request = (HttpServletRequest)servletRequest;
         HttpServletResponse response = (HttpServletResponse)servletResponse;
         ThreadContext.put("ipAddress", request.getRemoteAddr());
         HttpSession session = request.getSession(false);
         TimeZone timeZone = null;
         if (session != null) {
             // Something should set this after authentication completes
             String loginId = (String)session.getAttribute("LoginId");
             if (loginId != null) {
                 ThreadContext.put("loginId", loginId);
             }
             // This assumes there is some javascript on the user's page to create the cookie.
             if (session.getAttribute(TZ_NAME) == null) {
                 if (request.getCookies() != null) {
                     for (Cookie cookie : request.getCookies()) {
                         if (TZ_NAME.equals(cookie.getName())) {
                             int tzOffsetMinutes = Integer.parseInt(cookie.getValue());
                             timeZone = TimeZone.getTimeZone("GMT");
                             timeZone.setRawOffset((int)(tzOffsetMinutes * DateUtils.MILLIS_PER_MINUTE));
                             request.getSession().setAttribute(TZ_NAME, tzOffsetMinutes);
                             cookie.setMaxAge(0);
                             response.addCookie(cookie);
                         }
                     }
                 }
             }
         }
         ThreadContext.put("hostname", servletRequest.getServerName());
         ThreadContext.put("productName", filterConfig.getInitParameter("ProductName"));
         ThreadContext.put("locale", servletRequest.getLocale().getDisplayName());
         if (timeZone == null) {
             timeZone = TimeZone.getDefault();
         }
         ThreadContext.put("timezone", timeZone.getDisplayName());
         filterChain.doFilter(servletRequest, servletResponse);
         ThreadContext.clear();
     }

     public void destroy() {
     }
 }</pre>
             <p>Sample class that uses EventLogger.</p>
             <pre class="prettyprint linenums">
 import org.apache.logging.log4j.StructuredDataMessage;
 import org.apache.logging.log4j.EventLogger;

 import java.util.Date;
 import java.util.UUID;

 public class MyApp {

     public String doFundsTransfer(Account toAccount, Account fromAccount, long amount) {
         toAccount.deposit(amount);
         fromAccount.withdraw(amount);
         String confirm = UUID.randomUUID().toString();
         StructuredDataMessage msg = new StructuredDataMessage(confirm, null, "transfer");
         msg.put("toAccount", toAccount);
         msg.put("fromAccount", fromAccount);
         msg.put("amount", amount);
         EventLogger.logEvent(msg);
         return confirm;
     }
 }</pre>
             <p>The EventLogger class uses a Logger named "EventLogger". EventLogger uses a logging level
               of OFF as the default to indicate that it cannot be filtered. These events can be
               formatted for printing using the
               <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/layout/StructuredDataLayout.html">StructuredDataLayout</a>.
             </p>
           </subsection>
         </section>
     </body>
 </document>
	<?xml version="1.0"?>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->

	<document xmlns="http://maven.apache.org/XDOC/2.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
	<properties>
	<title>Log4j 2 API</title>
	<author email="rgoers@apache.org">Ralph Goers</author>
	</properties>

	<body>
	<section name="Log4j 2 API">
	<a name="EventLogging"/>
	<subsection name="Event Logging">
	<p>
	The EventLogger class provides a simple mechanism for logging events that occur in an application.
	While the EventLogger is useful as a way of initiating events that should be processed by an audit
	Logging system, by itself it does not implement any of the features an audit logging system would require
	such as guaranteed delivery.
	</p>
	<p>The recommended way of using the EventLogger in a typical web application is to populate
	the ThreadContext Map with data that is related to the entire lifespan of the request such as the user's
	id, the user's IP address, the product name, etc. This can easily be done in a servlet filter where
	the ThreadContext Map can also be cleared at the end of the request. When an event that needs to be
	recorded occurs a StructuredDataMessage should be created and populated.
	Then call EventLogger.logEvent(msg) where msg is a reference to the StructuredDataMessage.</p>

	<pre class="prettyprint linenums">
	import org.apache.logging.log4j.ThreadContext;
	import org.apache.commons.lang.time.DateUtils;

	import javax.servlet.Filter;
	import javax.servlet.FilterConfig;
	import javax.servlet.ServletException;
	import javax.servlet.ServletRequest;
	import javax.servlet.ServletResponse;
	import javax.servlet.FilterChain;
	import javax.servlet.http.HttpSession;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.Cookie;
	import javax.servlet.http.HttpServletResponse;
	import java.io.IOException;
	import java.util.TimeZone;

	public class RequestFilter implements Filter {
	private FilterConfig filterConfig;
	private static String TZ_NAME = "timezoneOffset";

	public void init(FilterConfig filterConfig) throws ServletException {
	this.filterConfig = filterConfig;
	}

	/**
	* Sample filter that populates the MDC on every request.
	*/
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
	throws IOException, ServletException {
	HttpServletRequest request = (HttpServletRequest)servletRequest;
	HttpServletResponse response = (HttpServletResponse)servletResponse;
	ThreadContext.put("ipAddress", request.getRemoteAddr());
	HttpSession session = request.getSession(false);
	TimeZone timeZone = null;
	if (session != null) {
	// Something should set this after authentication completes
	String loginId = (String)session.getAttribute("LoginId");
	if (loginId != null) {
	ThreadContext.put("loginId", loginId);
	}
	// This assumes there is some javascript on the user's page to create the cookie.
	if (session.getAttribute(TZ_NAME) == null) {
	if (request.getCookies() != null) {
	for (Cookie cookie : request.getCookies()) {
	if (TZ_NAME.equals(cookie.getName())) {
	int tzOffsetMinutes = Integer.parseInt(cookie.getValue());
	timeZone = TimeZone.getTimeZone("GMT");
	timeZone.setRawOffset((int)(tzOffsetMinutes * DateUtils.MILLIS_PER_MINUTE));
	request.getSession().setAttribute(TZ_NAME, tzOffsetMinutes);
	cookie.setMaxAge(0);
	response.addCookie(cookie);
	}
	}
	}
	}
	}
	ThreadContext.put("hostname", servletRequest.getServerName());
	ThreadContext.put("productName", filterConfig.getInitParameter("ProductName"));
	ThreadContext.put("locale", servletRequest.getLocale().getDisplayName());
	if (timeZone == null) {
	timeZone = TimeZone.getDefault();
	}
	ThreadContext.put("timezone", timeZone.getDisplayName());
	filterChain.doFilter(servletRequest, servletResponse);
	ThreadContext.clear();
	}

	public void destroy() {
	}
	}</pre>
	<p>Sample class that uses EventLogger.</p>
	<pre class="prettyprint linenums">
	import org.apache.logging.log4j.StructuredDataMessage;
	import org.apache.logging.log4j.EventLogger;

	import java.util.Date;
	import java.util.UUID;

	public class MyApp {

	public String doFundsTransfer(Account toAccount, Account fromAccount, long amount) {
	toAccount.deposit(amount);
	fromAccount.withdraw(amount);
	String confirm = UUID.randomUUID().toString();
	StructuredDataMessage msg = new StructuredDataMessage(confirm, null, "transfer");
	msg.put("toAccount", toAccount);
	msg.put("fromAccount", fromAccount);
	msg.put("amount", amount);
	EventLogger.logEvent(msg);
	return confirm;
	}
	}</pre>
	<p>The EventLogger class uses a Logger named "EventLogger". EventLogger uses a logging level
	of OFF as the default to indicate that it cannot be filtered. These events can be
	formatted for printing using the
	<a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/layout/StructuredDataLayout.html">StructuredDataLayout</a>.
	</p>
	</subsection>
	</section>
	</body>
	</document>