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1 <?xml version="1.0"?>
2 <!--
3 Licensed to the Apache Software Foundation (ASF) under one or more
4 contributor license agreements. See the NOTICE file distributed with
5 this work for additional information regarding copyright ownership.
6 The ASF licenses this file to You under the Apache License, Version 2.0
7 (the "License"); you may not use this file except in compliance with
8 the License. You may obtain a copy of the License at
9
10 http://www.apache.org/licenses/LICENSE-2.0
11
12 Unless required by applicable law or agreed to in writing, software
13 distributed under the License is distributed on an "AS IS" BASIS,
14 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 See the License for the specific language governing permissions and
16 limitations under the License.
17 -->
18
19 <document xmlns="http://maven.apache.org/XDOC/2.0"
20 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
21 xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
22 <properties>
23 <title>Log4j 2 API</title>
24 <author email="rgoers@apache.org">Ralph Goers</author>
25 </properties>
26
27 <body>
28 <section name="Log4j 2 API">
29 <a name="EventLogging"/>
30 <subsection name="Event Logging">
31 <p>
32 The EventLogger class provides a simple mechanism for logging events that occur in an application.
33 While the EventLogger is useful as a way of initiating events that should be processed by an audit
34 Logging system, by itself it does not implement any of the features an audit logging system would require
35 such as guaranteed delivery.
36 </p>
37 <p>The recommended way of using the EventLogger in a typical web application is to populate
38 the ThreadContext Map with data that is related to the entire lifespan of the request such as the user's
39 id, the user's IP address, the product name, etc. This can easily be done in a servlet filter where
40 the ThreadContext Map can also be cleared at the end of the request. When an event that needs to be
41 recorded occurs a StructuredDataMessage should be created and populated.
42 Then call EventLogger.logEvent(msg) where msg is a reference to the StructuredDataMessage.</p>
43
44 <pre class="prettyprint linenums">
45 import org.apache.logging.log4j.ThreadContext;
46 import org.apache.commons.lang.time.DateUtils;
47
48 import javax.servlet.Filter;
49 import javax.servlet.FilterConfig;
50 import javax.servlet.ServletException;
51 import javax.servlet.ServletRequest;
52 import javax.servlet.ServletResponse;
53 import javax.servlet.FilterChain;
54 import javax.servlet.http.HttpSession;
55 import javax.servlet.http.HttpServletRequest;
56 import javax.servlet.http.Cookie;
57 import javax.servlet.http.HttpServletResponse;
58 import java.io.IOException;
59 import java.util.TimeZone;
60
61 public class RequestFilter implements Filter {
62 private FilterConfig filterConfig;
63 private static String TZ_NAME = "timezoneOffset";
64
65 public void init(FilterConfig filterConfig) throws ServletException {
66 this.filterConfig = filterConfig;
67 }
68
69 /**
70 * Sample filter that populates the MDC on every request.
71 */
72 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
73 throws IOException, ServletException {
74 HttpServletRequest request = (HttpServletRequest)servletRequest;
75 HttpServletResponse response = (HttpServletResponse)servletResponse;
76 ThreadContext.put("ipAddress", request.getRemoteAddr());
77 HttpSession session = request.getSession(false);
78 TimeZone timeZone = null;
79 if (session != null) {
80 // Something should set this after authentication completes
81 String loginId = (String)session.getAttribute("LoginId");
82 if (loginId != null) {
83 ThreadContext.put("loginId", loginId);
84 }
85 // This assumes there is some javascript on the user's page to create the cookie.
86 if (session.getAttribute(TZ_NAME) == null) {
87 if (request.getCookies() != null) {
88 for (Cookie cookie : request.getCookies()) {
89 if (TZ_NAME.equals(cookie.getName())) {
90 int tzOffsetMinutes = Integer.parseInt(cookie.getValue());
91 timeZone = TimeZone.getTimeZone("GMT");
92 timeZone.setRawOffset((int)(tzOffsetMinutes * DateUtils.MILLIS_PER_MINUTE));
93 request.getSession().setAttribute(TZ_NAME, tzOffsetMinutes);
94 cookie.setMaxAge(0);
95 response.addCookie(cookie);
96 }
97 }
98 }
99 }
100 }
101 ThreadContext.put("hostname", servletRequest.getServerName());
102 ThreadContext.put("productName", filterConfig.getInitParameter("ProductName"));
103 ThreadContext.put("locale", servletRequest.getLocale().getDisplayName());
104 if (timeZone == null) {
105 timeZone = TimeZone.getDefault();
106 }
107 ThreadContext.put("timezone", timeZone.getDisplayName());
108 filterChain.doFilter(servletRequest, servletResponse);
109 ThreadContext.clear();
110 }
111
112 public void destroy() {
113 }
114 }</pre>
115 <p>Sample class that uses EventLogger.</p>
116 <pre class="prettyprint linenums">
117 import org.apache.logging.log4j.StructuredDataMessage;
118 import org.apache.logging.log4j.EventLogger;
119
120 import java.util.Date;
121 import java.util.UUID;
122
123 public class MyApp {
124
125 public String doFundsTransfer(Account toAccount, Account fromAccount, long amount) {
126 toAccount.deposit(amount);
127 fromAccount.withdraw(amount);
128 String confirm = UUID.randomUUID().toString();
129 StructuredDataMessage msg = new StructuredDataMessage(confirm, null, "transfer");
130 msg.put("toAccount", toAccount);
131 msg.put("fromAccount", fromAccount);
132 msg.put("amount", amount);
133 EventLogger.logEvent(msg);
134 return confirm;
135 }
136 }</pre>
137 <p>The EventLogger class uses a Logger named "EventLogger". EventLogger uses a logging level
138 of OFF as the default to indicate that it cannot be filtered. These events can be
139 formatted for printing using the
140 <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/layout/StructuredDataLayout.html">StructuredDataLayout</a>.
141 </p>
142 </subsection>
143 </section>
144 </body>
145 </document>