6、日志

6.1、日志工厂

如果一个数据库操作，出现了异常，我们需要排错。日志就是最好的助手！

曾经：sout、debug

现在：日志工厂

SLF4J
LOG4J【掌握】
LOG4J2
JDK_LOGGING
COMMONS_LOGGING
STDOUT_LOGGING【掌握】
NO_LOGGING

在Mybatis中具体使用那个日志实现，在设置中设定！

STDOUT_LOGGING标准日志输出

在mybatis核心配置文件中，配置我们的日志！

<settings>

        <setting name="logImpl" value="STDOUT_LOGGING"/>

</settings>

6.2、Log4j

什么事log4j

Log4j是Apache的一个开源项目，通过使用Log4j，我们可以控制日志信息输送的目的地是控制台、文件、GUI组件
我们也可以控制每一条日志的输出格式
通过定义每一条日志信息的级别，我们能够更加细致地控制日志的生成过程。
通过一个配置文件来灵活地进行配置，而不需要修改应用的代码。

1.先导入log4j的包

    <dependencies>

        <!-- https://mvnrepository.com/artifact/log4j/log4j -->

        <dependency>

            <groupId>log4j</groupId>

            <artifactId>log4j</artifactId>

            <version>1.2.17</version>

        </dependency>

    </dependencies>

2.log4j.properties

log4j.rootLogger=debug, stdout, R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.

log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

log4j.appender.R=org.apache.log4j.RollingFileAppender

log4j.appender.R.File=example.log

log4j.appender.R.MaxFileSize=100KB

# Keep one backup file

log4j.appender.R.MaxBackupIndex=5

log4j.appender.R.layout=org.apache.log4j.PatternLayout

log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

3.配置log4j为日志实现

    <settings>

        <setting name="logImpl" value="LOG4J"/>

    </settings>

4.log4j的使用！直接测试运行刚才的查询

DEBUG [main] (LogFactory.java:105) - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.

DEBUG [main] (LogFactory.java:105) - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.

DEBUG [main] (PooledDataSource.java:353) - PooledDataSource forcefully closed/removed all connections.

DEBUG [main] (PooledDataSource.java:353) - PooledDataSource forcefully closed/removed all connections.

DEBUG [main] (PooledDataSource.java:353) - PooledDataSource forcefully closed/removed all connections.

DEBUG [main] (PooledDataSource.java:353) - PooledDataSource forcefully closed/removed all connections.

DEBUG [main] (JdbcTransaction.java:136) - Opening JDBC Connection

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

DEBUG [main] (PooledDataSource.java:424) - Created connection 2049051802.

DEBUG [main] (JdbcTransaction.java:100) - Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@7a220c9a]

DEBUG [main] (BaseJdbcLogger.java:143) - ==>  Preparing: /*定义sql*/ select * from mybatis.user where id = ?;

DEBUG [main] (BaseJdbcLogger.java:143) - ==> Parameters: 1(Integer)

DEBUG [main] (BaseJdbcLogger.java:143) - <==      Total: 1

User{id=1, name='狂神', password='123456'}

DEBUG [main] (JdbcTransaction.java:122) - Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@7a220c9a]

DEBUG [main] (JdbcTransaction.java:90) - Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@7a220c9a]

DEBUG [main] (PooledDataSource.java:381) - Returned connection 2049051802 to pool.

Disconnected from the target VM, address: '127.0.0.1:58296', transport: 'socket'

Process finished with exit code 0

简单使用

在要使用Log4j 的类中，导入org.apache.log4j.Logger;

日志对象，加载参数为当前类的class

 static Logger logger = Logger.getLogger(UserDaoTest.class);

日志级别

logger.info("info:进入了testLog4j方法");

logger.debug("debug:进入了testLog4j");

logger.error("error:进入了testLog4j");

巴特西

MyBatis-06-日志

6、日志

6.1、日志工厂

6.2、Log4j

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