log4j的使用

       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，甚至是套接口服务器、NT的事件记录器、UNIX Syslog守护进程等；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。最令人感兴趣的就是，这些可以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。

配置

1.在maven中加入依赖包,slf4j-log4j12、log4j

<dependency>
   <groupId>org.slf4j</groupId>
   <artifactId>slf4j-log4j12</artifactId>
   <version>${slf4j.version}</version>
</dependency>
<dependency>
   <groupId>log4j</groupId>
   <artifactId>log4j</artifactId>
   <version>${log4j.version}</version>
</dependency>
<dependency>


<log4j.version>1.2.16</log4j.version>
<slf4j.version>1.6.1</slf4j.version>

2.在CLASSPATH下建立log4j.properties。内容如下(数字为行号)：

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

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
    <appender name="stdout" class="org.apache.log4j.ConsoleAppender">
        <param name="Encoding" value="UTF-8" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%c - %m%n" />
        </layout>
    </appender>

    <appender name="fileError" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="File" value="../logs/scm.log" />
        <param name="Encoding" value="UTF-8" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{yy-MM-dd HH:mm:ss} %m %n" />
        </layout>
    </appender>
<!-- 开发环境 -->    
    <logger name="com.gta.scm" additivity="true">
        <level value="debug" />
        <appender-ref ref="stdout" />
        <appender-ref ref="fileError" />
    </logger>
    <logger name="org.springframework" additivity="true">
        <level value="error" />
        <appender-ref ref="stdout" />
        <appender-ref ref="fileError" />
    </logger>
     <logger name="org.mybatis" additivity="true"> 
        <level value="error" />
        <appender-ref ref="stdout" />
        <appender-ref ref="fileError" />
     </logger>

    <logger name="java.sql.Connection" additivity="true">
        <level value="debug" />
        <appender-ref ref="stdout" />
        <appender-ref ref="fileError" />
    </logger>

    <logger name="java.sql.Statement" additivity="true">
        <level value="debug" />
        <appender-ref ref="stdout" />
        <appender-ref ref="fileError" />
    </logger>

    <logger name="java.sql.PreparedStatement" additivity="true">
        <level value="debug" />
        <appender-ref ref="stdout" />
        <appender-ref ref="fileError" />
    </logger>
    
    <logger name="java.sql.ResultSet" additivity="true"> 
         <level value="error" />
         <appender-ref ref="stdout" />
     </logger>     
     <logger name="org.apache.ibatis.logging.jdbc.ConnectionLogger" additivity="true"> 
         <level value="debug" />
         <appender-ref ref="stdout" />
     </logger> 
<!-- 生产环境 -->
     <!-- <root>
        <level value="error" />
        <appender-ref ref="fileError" />
    </root>  -->
</log4j:configuration>

3.在要输出日志的类中加入相关语句：

public class SimpleLogger {

    private Logger simpleLogger = null;

    static class SingletonHolder {
        static SimpleLogger instance = new SimpleLogger();
    }

    public static SimpleLogger getLogger() {
        return SingletonHolder.instance;
    }

    public static SimpleLogger getLogger(Class<?> clazz) {
        return new SimpleLogger(clazz);
    }

    private SimpleLogger() {
        simpleLogger = null;
        simpleLogger = LoggerFactory.getLogger("pango logger");
    }

    private SimpleLogger(Class<?> clazz) {
        simpleLogger = LoggerFactory.getLogger(clazz);
    }

    public void error(String message) {
        simpleLogger.error(message);
    }

    public void error(String message, Throwable t) {
        simpleLogger.error(message, t);
    }

    public void error(String format, Object arg1, Object arg2) {
        simpleLogger.error(format, arg1, arg2);
    }

    public void error(String format, Object... args) {
        simpleLogger.error(format, args);
    }

    public void debug(String message) {
        simpleLogger.debug(message);
    }

    public void debug(String message, Throwable t) {
        simpleLogger.debug(message, t);
    }

    public void warn(String message) {
        simpleLogger.warn(message);
    }

    public void warn(String message, Throwable t) {
        simpleLogger.warn(message, t);
    }
    
    public void warn(String format, Object... args) {
        simpleLogger.warn(format, args);
    }

    public void info(String message) {
        simpleLogger.info(message);
    }

    public void info(String message, Throwable t) {
        simpleLogger.info(message, t);
    }

    public boolean isDebugEnabled() {
        return simpleLogger.isDebugEnabled();
    }
}

4.在项目中的使用

private static SimpleLogger logger = SimpleLogger.getLogger(SpringContextHelper.class);

或者直接用org.slf4j.LoggerFactory

private static final Logger logger = LoggerFactory.getLogger(SalesManageController.class);

logger.error(e.getMessage(), e);