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| <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>Extending Log4j 2 Configuration</title> |
| <author email="rgoers@apache.org">Ralph Goers</author> |
| </properties> |
| |
| <body> |
| <section name="Programmatic Configuration"> |
| <p> |
| Log4j 2 provides a few ways for applications to create their own programmatic configuration: |
| </p> |
| <ul> |
| <li>Specify a custom ConfigurationFactory to start Log4j with a programmatic configuration</li> |
| <li>Use the Configurator to replace the configuration after Log4j started</li> |
| <li>Initialize Log4j with a combination of a configuration file and programmatic configuration</li> |
| <li>Modify the current Configuration after initialization</li> |
| </ul> |
| <a name="ConfigurationBuilder"/> |
| <subsection name="The ConfigurationBuilder API"> |
| <p> |
| Starting with release 2.4, Log4j provides a ConfigurationBuilder and a set of component builders that |
| allow a Configuration to be created fairly easily. |
| Actual configuration objects like LoggerConfig or Appender can be unwieldy; they require a lot |
| of knowledge about Log4j internals which makes them difficult to work with if all you want is to |
| create a Configuration. |
| </p> |
| <p> |
| The new ConfigurationBuilder API (in the <code>org.apache.logging.log4j.core.config.builder.api</code> package) |
| allows users to create Configurations in code by constructing component <i>definitions</i>. |
| There is no need to work directly with actual configuration objects. |
| Component definitions are added to the ConfigurationBuilder, and once all the definitions have |
| been collected all the actual configuration objects (like Loggers and Appenders) are constructed. |
| </p> |
| <p> |
| ConfigurationBuilder has convenience methods for the base components that can be configured such as |
| Loggers, Appenders, Filter, Properties, etc. |
| However, Log4j 2's plugin mechanism means that users can create any number of custom components. |
| As a trade-off, the ConfigurationBuilder API provides only a limited number of "strongly typed" |
| convenience methods like <code>newLogger()</code>, <code>newLayout()</code> etc. |
| The generic <code>builder.newComponent()</code> method can be used if no convenience method exists |
| for the component you want to configure. |
| </p> |
| <p> |
| For example, the builder does not know what sub-components can be configured on specific components |
| such as the RollingFileAppender vs. the RoutingAppender. To specify a triggering policy on a |
| RollingFileAppender you would use builder.newComponent(). |
| </p> |
| <p> |
| Examples of using the ConfigurationBuilder API are in the sections that follow. |
| </p> |
| </subsection> |
| <a name="ConfigurationFactory"/> |
| <subsection name="Understanding ConfigurationFactory"> |
| <p> |
| During initialization, Log4j 2 will search for available <a href="extending.html#ConfigurationFactory">ConfigurationFactories</a> |
| and then select the one to use. The |
| selected ConfigurationFactory creates the Configuration that Log4j will use. Here is how Log4j finds |
| the available ConfigurationFactories: |
| </p> |
| <ol> |
| <li>A system property named <tt>log4j2.configurationFactory</tt> can be set with the name of the ConfigurationFactory to be used.</li> |
| <li><code>ConfigurationFactory.setConfigurationFactory(ConfigurationFactory)</code> can be called with the instance of the |
| ConfigurationFactory to be used. This must be called before any other calls to Log4j.</li> |
| <li>A ConfigurationFactory implementation can be added to the classpath and configured as a plugin |
| in the "ConfigurationFactory" category. |
| The Order annotation can be used to specify the relative priority when multiple applicable |
| ConfigurationFactories are found.</li> |
| </ol> |
| <p> |
| ConfigurationFactories have the concept of "supported types", which basically maps to the |
| file extension of the configuration file that the ConfigurationFactory can handle. |
| If a configuration file location is specified, ConfigurationFactories whose supported type |
| does not include "*" or the matching file extension will not be used. |
| </p> |
| </subsection> |
| <a name="Example"/> |
| <subsection name="Initialize Log4j Using ConfigurationBuilder with a Custom ConfigurationFactory"> |
| <p> |
| One way to programmatically configure Log4j 2 is to create a custom ConfigurationFactory |
| that uses the <a href="#ConfigurationBuilder">ConfigurationBuilder</a> to create a Configuration. |
| The below example overrides the <code>getConfiguration()</code> method to return a |
| Configuration created by the ConfigurationBuilder. |
| This will cause the Configuration to automatically be hooked into Log4j when the LoggerContext is created. |
| In the example below, because it specifies a supported type of "*" it will override any configuration files provided. |
| </p> |
| <pre class="prettyprint linenum"><![CDATA[ |
| @Plugin(name = "CustomConfigurationFactory", category = ConfigurationFactory.CATEGORY) |
| @Order(50) |
| public class CustomConfigurationFactory extends ConfigurationFactory { |
| |
| static Configuration createConfiguration(final String name, ConfigurationBuilder<BuiltConfiguration> builder) { |
| builder.setConfigurationName(name); |
| builder.setStatusLevel(Level.ERROR); |
| builder.add(builder.newFilter("ThresholdFilter", Filter.Result.ACCEPT, Filter.Result.NEUTRAL). |
| addAttribute("level", Level.DEBUG)); |
| AppenderComponentBuilder appenderBuilder = builder.newAppender("Stdout", "CONSOLE"). |
| addAttribute("target", ConsoleAppender.Target.SYSTEM_OUT); |
| appenderBuilder.add(builder.newLayout("PatternLayout"). |
| addAttribute("pattern", "%d [%t] %-5level: %msg%n%throwable")); |
| appenderBuilder.add(builder.newFilter("MarkerFilter", Filter.Result.DENY, |
| Filter.Result.NEUTRAL).addAttribute("marker", "FLOW")); |
| builder.add(appenderBuilder); |
| builder.add(builder.newLogger("org.apache.logging.log4j", Level.DEBUG). |
| add(builder.newAppenderRef("Stdout")). |
| addAttribute("additivity", false)); |
| builder.add(builder.newRootLogger(Level.ERROR).add(builder.newAppenderRef("Stdout"))); |
| return builder.build(); |
| } |
| |
| @Override |
| public Configuration getConfiguration(final LoggerContext loggerContext, final ConfigurationSource source) { |
| return getConfiguration(loggerContext, source.toString(), null); |
| } |
| |
| @Override |
| public Configuration getConfiguration(final LoggerContext loggerContext, final String name, final URI configLocation) { |
| ConfigurationBuilder<BuiltConfiguration> builder = newConfigurationBuilder(); |
| return createConfiguration(name, builder); |
| } |
| |
| @Override |
| protected String[] getSupportedTypes() { |
| return new String[] {"*"}; |
| } |
| }]]></pre> |
| <p> |
| As of version 2.7, the <code>ConfigurationFactory.getConfiguration()</code> methods take an |
| additional <code>LoggerContext</code> parameter. |
| </p> |
| </subsection> |
| <a name="Configurator"/> |
| <subsection name="Reconfigure Log4j Using ConfigurationBuilder with the Configurator"> |
| <p> |
| An alternative to a custom ConfigurationFactory is to configure with the <code>Configurator</code>. |
| Once a Configuration object has been constructed, it can be passed to one of the |
| <code>Configurator.initialize</code> methods to set up the Log4j configuration. |
| </p> |
| <p> |
| Using the Configurator in this manner allows the application control over when Log4j is initialized. |
| However, should any logging be attempted before Configurator.initialize() is called then the |
| default configuration will be used for those log events. |
| </p> |
| <pre class="prettyprint linenum"><![CDATA[ |
| ConfigurationBuilder<BuiltConfiguration> builder = ConfigurationBuilderFactory.newConfigurationBuilder(); |
| builder.setStatusLevel(Level.ERROR); |
| builder.setConfigurationName("BuilderTest"); |
| builder.add(builder.newFilter("ThresholdFilter", Filter.Result.ACCEPT, Filter.Result.NEUTRAL) |
| .addAttribute("level", Level.DEBUG)); |
| AppenderComponentBuilder appenderBuilder = builder.newAppender("Stdout", "CONSOLE").addAttribute("target", |
| ConsoleAppender.Target.SYSTEM_OUT); |
| appenderBuilder.add(builder.newLayout("PatternLayout") |
| .addAttribute("pattern", "%d [%t] %-5level: %msg%n%throwable")); |
| appenderBuilder.add(builder.newFilter("MarkerFilter", Filter.Result.DENY, Filter.Result.NEUTRAL) |
| .addAttribute("marker", "FLOW")); |
| builder.add(appenderBuilder); |
| builder.add(builder.newLogger("org.apache.logging.log4j", Level.DEBUG) |
| .add(builder.newAppenderRef("Stdout")).addAttribute("additivity", false)); |
| builder.add(builder.newRootLogger(Level.ERROR).add(builder.newAppenderRef("Stdout"))); |
| ctx = Configurator.initialize(builder.build()); |
| ]]></pre> |
| <p>This example shows how to create a configuration that includes a RollingFileAppender.</p> |
| <pre class="prettyprint linenum"><![CDATA[ |
| ConfigurationBuilder< BuiltConfiguration > builder = ConfigurationBuilderFactory.newConfigurationBuilder(); |
| |
| builder.setStatusLevel( Level.ERROR); |
| builder.setConfigurationName("RollingBuilder"); |
| // create a console appender |
| AppenderComponentBuilder appenderBuilder = builder.newAppender("Stdout", "CONSOLE").addAttribute("target", |
| ConsoleAppender.Target.SYSTEM_OUT); |
| appenderBuilder.add(builder.newLayout("PatternLayout") |
| .addAttribute("pattern", "%d [%t] %-5level: %msg%n%throwable")); |
| builder.add( appenderBuilder ); |
| // create a rolling file appender |
| LayoutComponentBuilder layoutBuilder = builder.newLayout("PatternLayout") |
| .addAttribute("pattern", "%d [%t] %-5level: %msg%n"); |
| ComponentBuilder triggeringPolicy = builder.newComponent("Policies") |
| .addComponent(builder.newComponent("CronTriggeringPolicy").addAttribute("schedule", "0 0 0 * * ?")) |
| .addComponent(builder.newComponent("SizeBasedTriggeringPolicy").addAttribute("size", "100M")); |
| appenderBuilder = builder.newAppender("rolling", "RollingFile") |
| .addAttribute("fileName", "target/rolling.log") |
| .addAttribute("filePattern", "target/archive/rolling-%d{MM-dd-yy}.log.gz") |
| .add(layoutBuilder) |
| .addComponent(triggeringPolicy); |
| builder.add(appenderBuilder); |
| |
| // create the new logger |
| builder.add( builder.newLogger( "TestLogger", Level.DEBUG ) |
| .add( builder.newAppenderRef( "rolling" ) ) |
| .addAttribute( "additivity", false ) ); |
| |
| builder.add( builder.newRootLogger( Level.DEBUG ) |
| .add( builder.newAppenderRef( "rolling" ) ) ); |
| LoggerContext ctx = Configurator.initialize(builder.build()); |
| ]]></pre> |
| </subsection> |
| |
| <a name="Hybrid"/> |
| <subsection name="Initialize Log4j by Combining Configuration File with Programmatic Configuration"> |
| <p> |
| Sometimes you want to configure with a configuration file but do some additional programmatic |
| configuration. A possible use case might be that you want to allow for a flexible configuration using XML |
| but at the same time make sure there are a few configuration elements that are always present that can't be removed. |
| </p> |
| <p> |
| The easiest way to achieve this is to extend one of the standard Configuration classes |
| (XMLConfiguration, JSONConfiguration) and then create a new ConfigurationFactory for the extended class. |
| After the standard configuration completes the custom configuration can be added to it. |
| </p> |
| <p> |
| The example below shows how to extend XMLConfiguration to manually add an Appender and a LoggerConfig |
| to the configuration. |
| </p> |
| <pre class="prettyprint linenums"> |
| @Plugin(name = "MyXMLConfigurationFactory", category = "ConfigurationFactory") |
| @Order(10) |
| public class MyXMLConfigurationFactory extends ConfigurationFactory { |
| |
| /** |
| * Valid file extensions for XML files. |
| */ |
| public static final String[] SUFFIXES = new String[] {".xml", "*"}; |
| |
| /** |
| * Return the Configuration. |
| * @param source The InputSource. |
| * @return The Configuration. |
| */ |
| public Configuration getConfiguration(InputSource source) { |
| return new MyXMLConfiguration(source, configFile); |
| } |
| |
| /** |
| * Returns the file suffixes for XML files. |
| * @return An array of File extensions. |
| */ |
| public String[] getSupportedTypes() { |
| return SUFFIXES; |
| } |
| } |
| |
| public class MyXMLConfiguration extends XMLConfiguration { |
| public MyXMLConfiguration(final ConfigurationFactory.ConfigurationSource configSource) { |
| super(configSource); |
| } |
| |
| @Override |
| protected void doConfigure() { |
| super.doConfigure(); |
| final LoggerContext ctx = (LoggerContext) LogManager.getContext(false); |
| final Layout layout = PatternLayout.createLayout(PatternLayout.SIMPLE_CONVERSION_PATTERN, config, null, |
| null,null, null); |
| final Appender appender = FileAppender.createAppender("target/test.log", "false", "false", "File", "true", |
| "false", "false", "4000", layout, null, "false", null, config); |
| appender.start(); |
| addAppender(appender); |
| LoggerConfig loggerConfig = LoggerConfig.createLogger("false", "info", "org.apache.logging.log4j", |
| "true", refs, null, config, null ); |
| loggerConfig.addAppender(appender, null, null); |
| addLogger("org.apache.logging.log4j", loggerConfig); |
| } |
| }</pre> |
| </subsection> |
| <a name="AddingToCurrent"/> |
| <subsection name="Programmatically Modifying the Current Configuration after Initialization"> |
| <p> |
| Applications sometimes have the need to customize logging separate from the actual configuration. |
| Log4j allows this although it suffers from a few limitations: |
| </p> |
| <ol> |
| <li>If the configuration file is changed the configuration will be reloaded and the manual changes |
| will be lost.</li> |
| <li>Modification to the running configuration requires that all the methods being called (addAppender |
| and addLogger) be synchronized.</li> |
| </ol> |
| <p> |
| As such, the recommended approach for customizing a configuration is to extend one of the standard |
| Configuration classes, override the setup method to first do super.setup() and then add the custom |
| Appenders, Filters and LoggerConfigs to the configuration before it is registered for use. |
| </p> |
| <p> |
| The following example adds an Appender and a new LoggerConfig using that Appender to the current |
| configuration. |
| </p> |
| <!-- TODO: update code example below with new plugin API --> |
| <pre class="prettyprint linenums"><![CDATA[ |
| final LoggerContext ctx = (LoggerContext) LogManager.getContext(false); |
| final Configuration config = ctx.getConfiguration(); |
| Layout layout = PatternLayout.createLayout(PatternLayout.SIMPLE_CONVERSION_PATTERN, config, null, |
| null,null, null); |
| Appender appender = FileAppender.createAppender("target/test.log", "false", "false", "File", "true", |
| "false", "false", "4000", layout, null, "false", null, config); |
| appender.start(); |
| config.addAppender(appender); |
| AppenderRef ref = AppenderRef.createAppenderRef("File", null, null); |
| AppenderRef[] refs = new AppenderRef[] {ref}; |
| LoggerConfig loggerConfig = LoggerConfig.createLogger("false", "info", "org.apache.logging.log4j", |
| "true", refs, null, config, null ); |
| loggerConfig.addAppender(appender, null, null); |
| config.addLogger("org.apache.logging.log4j", loggerConfig); |
| ctx.updateLoggers(); |
| }]]></pre> |
| </subsection> |
| <a name="AppendingToWritersAndOutputStreams"/> |
| <subsection name="Appending Log Events to Writers and OutputStreams Programmatically"> |
| <p> |
| Log4j 2.5 provides facilities to append log events to Writers and OutputStreams. For example, this |
| provides simple integration for JDBC Driver implementors that use Log4j internally and still want |
| to support the JDBC APIs <code>CommonDataSource.setLogWriter(PrintWriter)</code>, |
| <code>java.sql.DriverManager.setLogWriter(PrintWriter)</code>, and |
| <code>java.sql.DriverManager.setLogStream(PrintStream)</code>. |
| </p> |
| <p> |
| Given any <code>Writer</code>, like a <code>PrintWriter</code>, you tell Log4j to append events to |
| that writer by creating a <code>WriterAppender</code> and updating the Log4j configuration: |
| </p> |
| <pre class="prettyprint linenums"><![CDATA[ |
| void addAppender(final Writer writer, final String writerName) { |
| final LoggerContext context = LoggerContext.getContext(false); |
| final Configuration config = context.getConfiguration(); |
| final PatternLayout layout = PatternLayout.createDefaultLayout(config); |
| final Appender appender = WriterAppender.createAppender(layout, null, writer, writerName, false, true); |
| appender.start(); |
| config.addAppender(appender); |
| updateLoggers(appender, config); |
| } |
| |
| private void updateLoggers(final Appender appender, final Configuration config) { |
| final Level level = null; |
| final Filter filter = null; |
| for (final LoggerConfig loggerConfig : config.getLoggers().values()) { |
| loggerConfig.addAppender(appender, level, filter); |
| } |
| config.getRootLogger().addAppender(appender, level, filter); |
| }]]></pre> |
| <p> |
| You can achieve the same effect with an <code>OutputStream</code>, like a <code>PrintStream</code>: |
| </p> |
| <pre class="prettyprint linenums"><![CDATA[ |
| void addAppender(final OutputStream outputStream, final String outputStreamName) { |
| final LoggerContext context = LoggerContext.getContext(false); |
| final Configuration config = context.getConfiguration(); |
| final PatternLayout layout = PatternLayout.createDefaultLayout(config); |
| final Appender appender = OutputStreamAppender.createAppender(layout, null, outputStream, outputStreamName, false, true); |
| appender.start(); |
| config.addAppender(appender); |
| updateLoggers(appender, config); |
| }]]></pre> |
| </subsection> |
| <p> |
| The difference is the use of <code>OutputStreamAppender</code> instead of <code>WriterAppender</code>. |
| </p> |
| </section> |
| |
| </body> |
| </document> |