常见问题解答

<dependencies>
  <dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
    <scope>provided</scope>
  </dependency>
</dependencies>

<dependencies>
  <dependency>
    <groupId>com.example</groupId>
    <artifactId>example-project</artifactId>
    <version>1.0</version>
    <exclusions>
      <exclusion>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
      </exclusion>
      <exclusion>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
      </exclusion>
    </exclusions>
  </dependency>
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.23.1</version>
  </dependency>
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-slf4j-impl</artifactId>
    <version>2.23.1</version>
  </dependency>
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-1.2-api</artifactId>
    <version>2.23.1</version>
  </dependency>
</dependencies>

configurations {
  all*.exclude group: 'log4j', module: 'log4j'
}

dependencies {
  compile('com.example:example-project:1.0') {
    exclude group: 'log4j', module: 'log4j'
    exclude group: 'org.slf4j', module: 'slf4j-log4j12'
  }
  compile('org.apache.logging.log4j:log4j-core:2.23.1')
  compile('org.apache.logging.log4j:log4j-slf4j-impl:2.23.1')
  compile('org.apache.logging.log4j:log4j-1.2-api:2.23.1')
}

// import org.apache.logging.log4j.core.LoggerContext;

LoggerContext context = (org.apache.logging.log4j.core.LoggerContext) LogManager.getContext(false);
File file = new File("path/to/a/different/log4j2.xml");

// this will force a reconfiguration
context.setConfigLocation(file.toURI());

import org.apache.logging.log4j.LogManager;

// ...

LogManager.shutdown();

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <File name="file" fileName="app.log">
      <PatternLayout>
        <Pattern>%d %p %c{1.} [%t] %m %ex%n</Pattern>
      </PatternLayout>
    </File>
    <Console name="STDOUT" target="SYSTEM_OUT">
      <PatternLayout pattern="%m%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="trace">
      <AppenderRef ref="file" level="DEBUG"/>
      <AppenderRef ref="STDOUT" level="INFO"/>
    </Root>
  </Loggers>
</Configuration>

<Routing name="Routing">
  <Routes pattern="$${ctx:ROUTINGKEY}">

    <!-- This route is chosen if ThreadContext has value 'special' for key ROUTINGKEY. -->
    <Route key="special">
      <RollingFile name="Rolling-${ctx:ROUTINGKEY}" fileName="logs/special-${ctx:ROUTINGKEY}.log"
	filePattern="./logs/${date:yyyy-MM}/${ctx:ROUTINGKEY}-special-%d{yyyy-MM-dd}-%i.log.gz">
	<PatternLayout>
	  <pattern>%d{ISO8601} [%t] %p %c{3} - %m%n</pattern>
	</PatternLayout>
	<Policies>
	  <TimeBasedTriggeringPolicy interval="6" modulate="true" />
          <SizeBasedTriggeringPolicy size="10 MB" />
	</Policies>
      </RollingFile>
    </Route>

    <!-- This route is chosen if ThreadContext has no value for key ROUTINGKEY. -->
    <Route key="$${ctx:ROUTINGKEY}">
      <RollingFile name="Rolling-default" fileName="logs/default.log"
	filePattern="./logs/${date:yyyy-MM}/default-%d{yyyy-MM-dd}-%i.log.gz">
        <PatternLayout>
	  <pattern>%d{ISO8601} [%t] %p %c{3} - %m%n</pattern>
        </PatternLayout>
        <Policies>
          <TimeBasedTriggeringPolicy interval="6" modulate="true" />
          <SizeBasedTriggeringPolicy size="10 MB" />
        </Policies>
      </RollingFile>
    </Route>

    <!-- This route is chosen if ThreadContext has a value for ROUTINGKEY
         (other than the value 'special' which had its own route above).
         The value dynamically determines the name of the log file. -->
    <Route>
      <RollingFile name="Rolling-${ctx:ROUTINGKEY}" fileName="logs/other-${ctx:ROUTINGKEY}.log"
	filePattern="./logs/${date:yyyy-MM}/${ctx:ROUTINGKEY}-other-%d{yyyy-MM-dd}-%i.log.gz">
	<PatternLayout>
	  <pattern>%d{ISO8601} [%t] %p %c{3} - %m%n</pattern>
	</PatternLayout>
	<Policies>
	  <TimeBasedTriggeringPolicy interval="6" modulate="true" />
	  <SizeBasedTriggeringPolicy size="10 MB" />
	</Policies>
      </RollingFile>
    </Route>
  </Routes>
</Routing>

// org.apache.logging.log4j.core.config.Configurator;

Configurator.setLevel("com.example.Foo", Level.DEBUG);

// You can also set the root logger:
Configurator.setRootLevel(Level.DEBUG);

package org.apache.logging.log4j.util;
public interface StringBuilderFormattable {
    /**
     * Writes a text representation of this object into the specified {@code StringBuilder},
     * ideally without allocating temporary objects.
     *
     * @param buffer the StringBuilder to write into
     */
     void formatTo(StringBuilder buffer);
}

-keep,allowoptimization class org.apache.logging.log4j.** { *; }