简明log4j配置教程

先准备好log4j需要对应的开发包：

apache-log4j-extras-1.2.17.jar

slf4j-api-1.6.1.jar

slf4j-log4j12-1.6.1.jar

然后就是在项目中准备一个log4j.xml开发文件:

<?xml version="1.0" encoding="UTF-8"?>  
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j='http://jakarta.apache.org/log4j/'>
    <!-- 设置按天滚动方式生成日志文件 -->
    <!-- 将日志写到文件中 -->
    <appender name="filelogger" class="org.apache.log4j.rolling.RollingFileAppender">
    <!-- 设置日志编码 -->
        <param name="Encoding" value="UTF-8" />
        <!-- 设置按天滚动方式生成日志文件 -->
        <rollingPolicy class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
            <param name="FileNamePattern" value="/opt/test/log/bi_%d{yyyyMMdd}.log" />
        </rollingPolicy>
        <!-- 设置日志内容格式  -->
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss.SSS} %p (%F.%L): %m%n" />
        </layout>
    </appender>
    
    <!-- 设置按天滚动方式生成日志文件 -->
    <!-- 将日志写到Linux系统日志中 -->
    <appender name="syslogger" class="org.apache.log4j.net.SyslogAppender">
    <!-- 设置阈值为ERROR级别，低于ERROR级别的日志将不会写入到系统中 -->
        <param name="Threshold" value="ERROR" />
        <param name="SyslogHost" value="192.168.172.140" />
        <param name="Facility" value="USER" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%p (%F.%L): %m%n" />
        </layout>
    </appender>

    <!-- 设置logger日志名称，在程序中引用 -->
    <logger name="logfile">
        <!-- 设置日志级别为DEBUG级别 -->
        <level value="debug" />
        <appender-ref ref="filelogger" />
        <appender-ref ref="syslogger" />
    </logger> 
</log4j:configuration>

关于上面日志格式常用占位符解释：

%d: 当前时间，如果要指定格式，则可以yyyy MM dd HH mm ss SSS 代表 年、月、日、时、分、秒、毫秒

%F: 日志所在代码所在文件

%L: 日志所在的行数

%m: 消息主体

%t: 程序所在线程

%n: 换行

%p: 当前日志级别

示例程序代码:

package org.lyk.action;

import java.text.SimpleDateFormat;
import java.util.Date;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;


@Controller
@RequestMapping("/test/*")
public class Test
{
    private Logger logger = LoggerFactory.getLogger("logfile");
    @RequestMapping("testDemo")
    public ModelAndView testDemo(String msg)
    {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
        logger.info("This is for log file " + sdf.format(new Date()));
        logger.error("This is for sys log file " + sdf.format(new Date()));
        return new ModelAndView("/index.jsp");
    }
}

输出效果

日志文件：

Linux syslog:

程序代码:

package org.lyk.action;

import java.text.SimpleDateFormat;
import java.util.Date;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;


@Controller
@RequestMapping("/test/*")
public class Test
{
    private Logger logger = LoggerFactory.getLogger("logfile");
    @RequestMapping("testDemo")
    public ModelAndView testDemo(String msg)
    {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
        logger.info("This is for log file " + sdf.format(new Date()));
        logger.error("This is for sys log file " + sdf.format(new Date()));
        return new ModelAndView("/index.jsp");
    }
}

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