Logging

MyBatis provides logging information through the use of an internal log factory. The internal log factory will delegate logging information to one of the following log implementations:

• SLF4J
• Apache Commons Logging
• Log4j 2
• Log4j (deprecated since 3.5.9)
• JDK logging

The logging solution chosen is based on runtime introspection by the internal MyBatis log factory. The MyBatis log factory will use the first logging implementation it finds (implementations are searched in the above order). If MyBatis finds none of the above implementations, then logging will be disabled.

Many environments ship Commons Logging as a part of the application server classpath (good examples include Tomcat and WebSphere). It is important to know that in such environments, MyBatis will use Commons Logging as the logging implementation. In an environment like WebSphere this will mean that your Log4J configuration will be ignored because WebSphere supplies its own proprietary implementation of Commons Logging. This can be very frustrating because it will appear that MyBatis is ignoring your Log4J configuration (in fact, MyBatis is ignoring your Log4J configuration because MyBatis will use Commons Logging in such environments). If your application is running in an environment where Commons Logging is included in the classpath but you would rather use one of the other logging implementations you can select a different logging implementation by adding a setting in mybatis-config.xml file as follows:

<configuration>
  <settings>
    ...
    <setting name="logImpl" value="LOG4J"/>
    ...
  </settings>
</configuration>

Valid values are SLF4J, LOG4J, LOG4J2, JDK_LOGGING, COMMONS_LOGGING, STDOUT_LOGGING, NO_LOGGING or a full qualified class name that implements org.apache.ibatis.logging.Log and gets an string as a constructor parameter.

You can also select the implementation by calling one of the following methods:

org.apache.ibatis.logging.LogFactory.useSlf4jLogging();
org.apache.ibatis.logging.LogFactory.useLog4JLogging();
org.apache.ibatis.logging.LogFactory.useLog4J2Logging();
org.apache.ibatis.logging.LogFactory.useJdkLogging();
org.apache.ibatis.logging.LogFactory.useCommonsLogging();
org.apache.ibatis.logging.LogFactory.useStdOutLogging();

If you choose to call one of these methods, you should do so before calling any other MyBatis method. Also, these methods will only switch to the requested log implementation if that implementation is available on the runtime classpath. For example, if you try to select Log4J2 logging and Log4J2 is not available at runtime, then MyBatis will ignore the request to use Log4J2 and will use it's normal algorithm for discovering logging implementations.

The specifics of SLF4J, Apache Commons Logging, Apache Log4J and the JDK Logging API are beyond the scope of this document. However the example configuration below should get you started. If you would like to know more about these frameworks, you can get more information from the following locations:

• SLF4J
• Apache Commons Logging
• Apache Log4j 1.x and 2.x
• JDK Logging API

<dependency>
  <groupId>ch.qos.logback</groupId>
  <artifactId>logback-classic</artifactId>
  <version>1.x.x</version>
</dependency>

package org.mybatis.example;
public interface BlogMapper {
  @Select("SELECT * FROM blog WHERE id = #{id}")
  Blog selectBlog(int id);
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration>
<configuration>

  <appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%5level [%thread] - %msg%n</pattern>
    </encoder>
  </appender>

  <logger name="org.mybatis.example.BlogMapper">
    <level value="trace"/>
  </logger>
  <root level="error">
    <appender-ref ref="stdout"/>
  </root>

</configuration>

<logger name="org.mybatis.example.BlogMapper.selectBlog">
  <level value="trace"/>
</logger>

<logger name="org.mybatis.example">
  <level value="trace"/>
</logger>

<logger name="org.mybatis.example">
  <level value="debug"/>
</logger>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.mybatis.example.BlogMapper">
  <select id="selectBlog" resultType="Blog">
    select * from Blog where id = #{id}
  </select>
</mapper>

<logger name="org.mybatis.example.BlogMapper">
  <level value="trace"/>
</logger>

<logger name="org.mybatis.example.BlogMapper.selectBlog">
  <level value="trace"/>
</logger>

<dependency>
  <groupId>org.apache.logging.log4j</groupId>
  <artifactId>log4j-core</artifactId>
  <version>2.x.x</version>
</dependency>

<?xml version="1.0" encoding="UTF-8"?>
<Configuration xmlns="http://logging.apache.org/log4j/2.0/config">

  <Appenders>
    <Console name="stdout" target="SYSTEM_OUT">
      <PatternLayout pattern="%5level [%t] - %msg%n"/>
    </Console>
  </Appenders>

  <Loggers>
    <Logger name="org.mybatis.example.BlogMapper" level="trace"/>
    <Root level="error" >
      <AppenderRef ref="stdout"/>
    </Root>
  </Loggers>

</Configuration>

<dependency>
  <groupId>log4j</groupId>
  <artifactId>log4j</artifactId>
  <version>1.2.17</version>
</dependency>

log4j.rootLogger=ERROR, stdout

log4j.logger.org.mybatis.example.BlogMapper=TRACE

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

handlers=java.util.logging.ConsoleHandler
.level=SEVERE

org.mybatis.example.BlogMapper=FINER

java.util.logging.ConsoleHandler.level=ALL
java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter
java.util.logging.SimpleFormatter.format=%1$tT.%1$tL %4$s %3$s - %5$s%6$s%n