| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> |
| <!-- |
| | Generated by Apache Maven Doxia at Jun 9, 2012 |
| | Rendered using Apache Maven Fluido Skin |
| --> |
| <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> |
| <meta name="viewport" content="width=device-width, initial-scale=1.0" /> |
| <title> |
| Log4j 2 API</title> |
| <link rel="stylesheet" href="../css/apache-maven-fluido.min.css" /> |
| <link rel="stylesheet" href="../css/site.css" /> |
| <link rel="stylesheet" href="../css/print.css" media="print" /> |
| |
| |
| <script type="text/javascript" src="../js/apache-maven-fluido.min.js"></script> |
| |
| |
| <meta name="author" content="Ralph Goers" /> |
| <meta name="Date-Revision-yyyymmdd" content="20120609" /> |
| <meta http-equiv="Content-Language" content="en" /> |
| |
| </head> |
| <body class="topBarDisabled"> |
| |
| |
| |
| |
| <div class="container-fluid"> |
| <div id="banner"> |
| <div class="pull-left"> |
| <a href="../../../" id="bannerLeft"> |
| <img src="../images/ls-logo.jpg" alt="Apache Logging Services™"/> |
| </a> |
| </div> |
| <div class="pull-right"> <div id="bannerRight"> |
| <img src="../images/logo.jpg" /> |
| </div> |
| </div> |
| <div class="clear"><hr/></div> |
| </div> |
| |
| <div id="breadcrumbs"> |
| <ul class="breadcrumb"> |
| |
| |
| <li id="publishDate">Last Published: 2012-06-09</li> |
| <li class="divider">|</li> <li id="projectVersion">Version: 2.0-alpha1-SNAPSHOT</li> |
| |
| |
| |
| |
| |
| <li class="pull-right"> <a href="http://wiki.apache.org/logging" class="externalLink" title="Logging Wiki">Logging Wiki</a> |
| </li> |
| |
| <li class="divider pull-right">|</li> |
| |
| <li class="pull-right"> <a href="http://www.apache.org/" class="externalLink" title="Apache">Apache</a> |
| </li> |
| |
| <li class="divider pull-right">|</li> |
| |
| <li class="pull-right"> <a href="../../../" title="Logging Services">Logging Services</a> |
| </li> |
| |
| <li class="divider pull-right">|</li> |
| |
| <li class="pull-right"> <a href="../../" title="Log4j">Log4j</a> |
| </li> |
| |
| <li class="divider pull-right">|</li> |
| |
| <li class="pull-right"> <a href="../../companions" title="Log4j Companions">Log4j Companions</a> |
| </li> |
| |
| </ul> |
| </div> |
| |
| <div class="row-fluid"> |
| <div id="leftColumn" class="span3"> |
| <div class="well sidebar-nav"> |
| |
| |
| <h3>Apache Log4j™ 2</h3> |
| <ul> |
| <li class="none"> |
| <a href="../index.html" title="About">About</a> |
| </li> |
| <li class="none"> |
| <a href="../download.html" title="Download">Download</a> |
| </li> |
| <li class="none"> |
| <a href="../build.html" title="Build and Install">Build and Install</a> |
| </li> |
| <li class="none"> |
| <a href="../changelog.html" title="Changelog">Changelog</a> |
| </li> |
| </ul> |
| <h3>Manual</h3> |
| <ul> |
| <li class="none"> |
| <a href="../manual/index.html" title="Introduction">Introduction</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/architecture.html" title="Architecture">Architecture</a> |
| </li> |
| <li class="expanded"> |
| <strong>API</strong> |
| <ul> |
| <li class="none"> |
| <a href="../manual/api.html#Overview" title="Overview">Overview</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/flowtracing.html" title="Flow Tracing">Flow Tracing</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/markers.html" title="Markers">Markers</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/eventlogging.html" title="Event Logging">Event Logging</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/messages.html" title="Messages">Messages</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/thread-context.html" title="ThreadContext">ThreadContext</a> |
| </li> |
| </ul> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/configuration.html" title="Configuration">Configuration</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/plugins.html" title="Plugins">Plugins</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/lookups.html" title="Lookups">Lookups</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/appenders.html" title="Appenders">Appenders</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/layouts.html" title="Layouts">Layouts</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/filters.html" title="Filters">Filters</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/jmx.html" title="JMX">JMX</a> |
| </li> |
| <li class="none"> |
| <a href="../manual/logsep.html" title="Logging Separation">Logging Separation</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../manual/extending.html" title="Extending Log4j">Extending Log4j</a> |
| </li> |
| </ul> |
| <h3>Logging Adapters</h3> |
| <ul> |
| <li class="none"> |
| <a href="../log4j12-api/api.html" title="Log4j 1.x API">Log4j 1.x API</a> |
| </li> |
| <li class="none"> |
| <a href="../log4j2-jcl/api.html" title="Commons Logging">Commons Logging</a> |
| </li> |
| <li class="none"> |
| <a href="../slf4j-impl/api.html" title="SLF4J">SLF4J</a> |
| </li> |
| </ul> |
| <h3>Components</h3> |
| <ul> |
| <li class="none"> |
| <a href="../log4j-api/index.html" title="API">API</a> |
| </li> |
| <li class="none"> |
| <a href="../log4j-core/index.html" title="Impl">Impl</a> |
| </li> |
| <li class="none"> |
| <a href="../log4j12-api/index.html" title="Log4J 1.2 API">Log4J 1.2 API</a> |
| </li> |
| <li class="none"> |
| <a href="../log4j-jcl/index.html" title="Commons Logging Bridge">Commons Logging Bridge</a> |
| </li> |
| <li class="none"> |
| <a href="../slf4j-impl/index.html" title="SLF4J Binding">SLF4J Binding</a> |
| </li> |
| <li class="none"> |
| <a href="../log4j-flume-og/index.html" title="Flume OG">Flume OG</a> |
| </li> |
| <li class="none"> |
| <a href="../log4j-flume-ng/index.html" title="Flume NG">Flume NG</a> |
| </li> |
| </ul> |
| <h3>Project Documentation</h3> |
| <ul> |
| <li class="collapsed"> |
| <a href="../project-info.html" title="Project Information">Project Information</a> |
| </li> |
| <li class="collapsed"> |
| <a href="../project-reports.html" title="Project Reports">Project Reports</a> |
| </li> |
| </ul> |
| |
| |
| |
| <hr class="divider" /> |
| |
| <div id="poweredBy"> |
| <div class="clear"></div> |
| <div class="clear"></div> |
| <div class="clear"></div> |
| <a href="http://maven.apache.org/" title="Built by Maven" class="poweredBy"> |
| <img class="poweredBy" alt="Built by Maven" src="../images/logos/maven-feather.png" /> |
| </a> |
| </div> |
| </div> |
| </div> |
| |
| <div id="bodyColumn" class="span9" > |
| |
| <!-- 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. --> |
| |
| <div class="section"><h2>Log4j 2 API<a name="Log4j_2_API"></a></h2> |
| <a name="Overview"></a> |
| <div class="section"><h3>Overview<a name="Overview"></a></h3> |
| <p> |
| The Log4Jj 2.0 API provides the interface that applications should code to and provides the |
| adapter components required for implementers to create a logging implementation. Although Log4j 2 |
| is broken up between an API and an implementation, the primary purpose of doing so was not to |
| allow multiple implementations, although that is certainly possible, but to clearly define |
| what classes and methods are safe to use in "normal" application code. |
| </p> |
| <div class="section"><h4>Hello World!<a name="Hello_World"></a></h4> |
| <p> |
| No introduction would be complete without the customary Hello, World example. Here is ours. First, |
| a Logger with the name "HelloWorld" is obtained from the LogManager. Next, the logger is used to |
| write the "Hello, World!" message, however the message will be written only if the Logger is |
| configured to allow informational messages. |
| </p> |
| <div class="source"><pre class="prettyprint"> import org.apache.logging.log4j.LogManager; |
| import org.apache.logging.log4j.Logger; |
| |
| public class HelloWorld { |
| private static Logger logger = LogManager.getLogger("HelloWorld"); |
| public static void main(String[] args) { |
| logger.info("Hello, World!"); |
| } |
| }</pre></div> |
| <p> |
| The output from the call to logger.info() will vary significantly depending on the configuration |
| used. See the <a href="./configuration.html">Configuration</a> section for more details. |
| </p> |
| </div><div class="section"><h4>Parameter Substitution<a name="Parameter_Substitution"></a></h4> |
| <p> |
| Frequently the purpose of logging is to provide information about what is happening in the system, |
| which requires including information about the objects being manipulated. In Log4j 1.x this could |
| be accomplished by doing: |
| </p> |
| <div class="source"><pre class="prettyprint"> if (logger.isDebugEnabled()) { |
| logger.debug("Logging in user " + user.getName() + " with id " + user.getId()); |
| }</pre></div> |
| <p> |
| Doing this repeatedly has the effect of making the code feel like it is more about logging than the |
| actual task at hand. In addition, it results in the logging level being checked twice; once on the |
| call to isDebugEnabled and once on the debug method. A better alternative would be: |
| </p> |
| <div class="source"><pre class="prettyprint"> logger.debug("Logging in user {} with id {}", user.getName(), user.getId());</pre></div> |
| <p> |
| With the code above the logging level will only be checked once and the String construction will |
| only occur when debug logging is enabled. |
| </p> |
| </div></div> |
| </div> |
| |
| |
| </div> |
| </div> |
| |
| <hr/> |
| |
| <footer> |
| <div class="container-fluid"> |
| <div class="row span16">Copyright © 1999-2012 |
| <a href="http://www.apache.org">Apache Software Foundation</a>. |
| All Rights Reserved. |
| |
| </div> |
| |
| |
| |
| </div> |
| </footer> |
| </body> |
| </html> |
