1.引入日志依赖包（pom.xml）

会自动引入log4j以及slf4j-api

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.5</version>
</dependency>

2.添加log4j.properties

log4j.rootLogger=DEBUG,A1
log4j.logger.org.apache=DEBUG
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c]-[%p] %m%n

再次运行程序会打印日志：

2018-06-30 19:53:37,554 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Opening JDBC Connection
2018-06-30 19:53:37,818 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Created connection 2094411587.
2018-06-30 19:53:37,818 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cd62f43]
2018-06-30 19:53:37,863 [main] [MyMapper.selectUser]-[DEBUG] ==> Preparing: select * from tb_user where id = ? 
2018-06-30 19:53:37,931 [main] [MyMapper.selectUser]-[DEBUG] ==> Parameters: 1(Integer)
2018-06-30 19:53:37,953 [main] [MyMapper.selectUser]-[DEBUG] <== Total: 1
User{id='1', userName='zpc', password='123456', name='鹏程', age=25, sex=1, birthday='1990-09-02', created='2018-06-30 18:20:18.0', updated='2018-06-30 18:20:18.0'}
2018-06-30 19:53:37,954 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cd62f43]
2018-06-30 19:53:37,954 [main] [org.apache.ibatis.transaction.jdbc.JdbcTransaction]-[DEBUG] Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@7cd62f43]
2018-06-30 19:53:37,955 [main] [org.apache.ibatis.datasource.pooled.PooledDataSource]-[DEBUG] Returned connection 2094411587 to pool.