log4j日志文件路径问题

做了一个最简单的servlet项目，只有一个servlet，然后想在servlet把日志记录到项目下的logs文件夹中的logRecord.log和logRecorderror.log。

然而路径问题弄了我一天，找了很多资料，绝对路径是可以解决，但是如果移植的话，那么绝对路径改起来会很麻烦。所以最好用相对路径。

但是网上的相关资料都无法解决我的问题，后来一不做二不休，瞎弄，发现路径直接写logs/logRecord.log竟然成功的把日志写入进去了。

好了，话不多说   直接上代码。

1.首先我们把

commons-logging-1.1.3.jar
log4j-1.2.17.jar

导入到项目中。

2.配置log4j.properties

### set log levels ###log4j.rootLogger = INFO, stdout, D, E#log4j.rootLogger = INFO, stdout#log.path = /mylog###　输出到控制台 ###log4j.appender.stdout = org.apache.log4j.ConsoleAppenderlog4j.appender.stdout.Target = System.outlog4j.appender.stdout.layout = org.apache.log4j.PatternLayoutlog4j.appender.stdout.layout.ConversionPattern =  %d{yyyy/MM/dd-HH:mm:ss} [%-5p] [%c] [%F] - %m %n### 输出到日志文件 ###log4j.appender.D = org.apache.log4j.DailyRollingFileAppenderlog4j.appender.D.File = logs/logRecord.loglog4j.appender.D.DatePattern='.'yyyy-MM-ddlog4j.appender.D.Threshold = INFOlog4j.appender.D.layout = org.apache.log4j.PatternLayoutlog4j.appender.D.layout.ConversionPattern = %d{yyyy/MM/dd-HH:mm:ss} [%-5p] [%c] [%F] - %m %nlog4j.appender.D.layout.Encoding=UTF-8### 保存异常信息到单独文件 ###log4j.appender.E = org.apache.log4j.DailyRollingFileAppender##异常日志文件log4j.appender.E.File = logs/logRecorderror.loglog4j.appender.E.Append = true##只输出ERROR级别以上的日志log4j.appender.E.Threshold = ERROR log4j.appender.E.layout = org.apache.log4j.PatternLayoutlog4j.appender.E.layout.ConversionPattern = %d{yyyy/MM/dd-HH:mm:ss} [%-5p] [%c] [%F] - %m %nlog4j.appender.E.DatePattern='.'yyyy-MM-ddlog4j.appender.E.Encoding=UTF-8

这个是servlet，里面的main方法是来把日志写入文件中。

package com.pingpay.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;public class PingPayLogServlet extends HttpServlet {// 在任何需要记录日志的类中Log log = LogFactory.getLog(this.getClass());/** * 记录ping++返回的数据 *  */public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//response.setContentType("text/html");//request.setCharacterEncoding("utf-8");//response.setCharacterEncoding("utf-8");log.info("into one method");try {System.out.println(9 / 0);} catch (RuntimeException e) {log.error(e.getMessage());}log.info("out one method");}public static void main(String[] args) throws Exception {new PingPayLogServlet().doPost(null, null);System.out.println("1");}}

项目结构如图。

因为我们在log4j.properties中设置了log4j.appender.D.Threshold = INFO，log4j.appender.E.Threshold = ERROR 。

所以error的日志会保存在logRecorderror.log文件中，

但是由于：DEBUG < INFO < WARN < ERROR < FATAL级别

log4j.appender.D.Threshold = INFO这句话 
它的作用是输出INFO级别以上的内容到logRecord.log中，所以logRecord.log文件中包含了ERROR级别的文件。

如有错误，请指出，谢谢。

周一回来发现上面的方法不行了。我也是醉了，然后换了一种方法。

将日志文件输出到自己程序WEB-INF\logs目录中

1、在web.xml配置一个servlet

<servlet> <servlet-name>lo4jInit</servlet-name> <servlet-class>com.linder.util.log4j.init.Lo4jInit</servlet-class> <init-param> <param-name>log4j_init_path</param-name> <param-value>WEB-INF\classes\log4j.properties</param-value> </init-param> <init-param> <param-name>log4j_file_path</param-name> <param-value>WEB-INF\logs\</param-value> </init-param> <load-on-startup>0</load-on-startup> </servlet>

2、编写一个初始化log4j的Servlet

package com.linder.util.log4j.init;import java.io.FileInputStream;import java.io.IOException;import java.util.Properties;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.log4j.Logger;import org.apache.log4j.PropertyConfigurator;public class Lo4jInit   extends HttpServlet {/** *  */private static final long serialVersionUID = 1L;private static Logger logger=Logger.getLogger(Lo4jInit.class);public void init(){String path=this.getServletContext().getRealPath("/");String file=this.getInitParameter("log4j_init_path");String logFile=this.getInitParameter("log4j_file_path");if(file!=null){Properties prop = new Properties(); try{prop.load(new FileInputStream(path+file)); //加载log4j.propertiesprop.setProperty("log4j.appender.R.File", path+logFile+ prop.getProperty("log4j.appender.R.File")); //设置日志文件的输出路径PropertyConfigurator.configure(prop); //加载配置项}catch(Exception e){logger.info("初始化log4j日志输入路径异常，请检查web.xml参数配置是否正常，异常发生在"+this.getClass().getName()+"类的public void init()方法，异常的愿意是："+e.getMessage(), e.fillInStackTrace());}}}protected void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {}}

 3、log4j.properties的配置信息

# Set root category priority to info and its only appender to console. log4j.rootCategory=info,console,R#log4j.debug=true# console is set to be a ConsoleAppender using a PatternLayout. log4j.appender.console=org.apache.log4j.ConsoleAppender log4j.appender.console.Threshold=info log4j.appender.console.layout=org.apache.log4j.PatternLayout log4j.appender.console.layout.ConversionPattern=- %m%n# R is set to be a File appender using a PatternLayout.log4j.appender.R=org.apache.log4j.RollingFileAppenderlog4j.appender.R.Append=truelog4j.appender.R.Threshold=info log4j.appender.R.MaxFileSize=1024KB log4j.appender.R.MaxBackupIndex=10log4j.appender.R.File=abc.loglog4j.appender.R.layout=org.apache.log4j.PatternLayoutlog4j.appender.R.layout.ConversionPattern=%-d{yyyy-MM-dd HH\:mm\:ss} [%c]-[%p] %m%n

abc.log位于你项目的WEB-INF/logs的文件夹下。

 我项目的XML配置为：

<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"><servlet><servlet-name>lo4jInit</servlet-name><servlet-class>com.pingpay.servlet.Lo4jInit</servlet-class><init-param><param-name>log4j_init_path</param-name><param-value>WEB-INF\classes\log4j.properties</param-value></init-param><init-param><param-name>log4j_file_path</param-name><param-value>WEB-INF\logs\</param-value></init-param><load-on-startup>0</load-on-startup></servlet><servlet><description>This is the description of my J2EE component</description><display-name>This is the display name of my J2EE component</display-name><servlet-name>PingPayServlet</servlet-name><servlet-class>com.pingpay.servlet.PingPayServlet</servlet-class></servlet><servlet-mapping><servlet-name>PingPayServlet</servlet-name><url-pattern>/PingPayServlet</url-pattern></servlet-mapping></web-app>