log4j简单使用java web项目--后台打印以及输出到文件

1，导入log4j-1.2.15.jar 

2，在src下面新建log4j.properties

其内容为

### 设置###
log4j.rootLogger = debug,stdout,D,E

### 输出信息到控制抬 ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = [%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS} method:%l%n%m%n

### 输出DEBUG 级别以上的日志到=E://logger_data/error.log ###
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
log4j.appender.D.File = E://logger_data/log.log
log4j.appender.D.Append = true
log4j.appender.D.Threshold = DEBUG
log4j.appender.D.layout = org.apache.log4j.PatternLayout
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n

### 输出ERROR 级别以上的日志到=E://logger_data/error.log ###
log4j.appender.E = org.apache.log4j.DailyRollingFileAppender
log4j.appender.E.File =E://logger_data/error.log
log4j.appender.E.Append = true
log4j.appender.E.Threshold = ERROR
log4j.appender.E.layout = org.apache.log4j.PatternLayout
log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss}  [ %t:%r ] - [ %p ]  %m%n

3，添加servlet 容器加载时初始化

package com.mucfc;
import java.io.File;
import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.PropertyConfigurator;

@WebServlet("/Log4JInitServlet")
public class Log4JInitServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public Log4JInitServlet() {
        super();
    }

    public void init(ServletConfig config) throws ServletException {
        System.out.println("Log4JInitServlet 正在初始化 log4j日志设置信息");
        String log4jLocation = config.getInitParameter("log4j-properties-location");

        ServletContext sc = config.getServletContext();

        if (log4jLocation == null) {
            System.err.println("*** 没有 log4j-properties-location 初始化的文件, 所以使用 BasicConfigurator初始化");
            BasicConfigurator.configure();
        } else {
            String webAppPath = sc.getRealPath("/");
            String log4jProp = webAppPath + log4jLocation;
            File yoMamaYesThisSaysYoMama = new File(log4jProp);
            if (yoMamaYesThisSaysYoMama.exists()) {
                System.out.println("使用: " + log4jProp+"初始化日志设置信息");
                PropertyConfigurator.configure(log4jProp);
            } else {
                System.err.println("*** " + log4jProp + " 文件没有找到， 所以使用 BasicConfigurator初始化");
                BasicConfigurator.configure();
            }
        }
        super.init(config);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }

}

4，添加servlet 测试类

package com.mucfc;
import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

@WebServlet("/Log4JTestServlet")
public class Log4JTestServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static Logger logger = Logger.getLogger(Log4JTestServlet.class);

    public Log4JTestServlet() {
        super();
    }

    public void init(ServletConfig config) throws ServletException {
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 记录debug级别的信息
        logger.debug("This is debug message.");
        // 记录info级别的信息
        logger.info("This is info message.");
        // 记录error级别的信息
        logger.error("This is error message.");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

}

5，修改web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app 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"
         version="3.0">
    <display-name>log4j</display-name>

    <!--用来启动 log4jConfigLocation的servlet -->
    <servlet>
        <servlet-name>Log4JInitServlet</servlet-name>
        <servlet-class>com.mucfc.Log4JInitServlet</servlet-class>
        <init-param>
            <param-name>log4j-properties-location</param-name>
            <param-value>/WEB-INF/classes/log4j.properties</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>


    <servlet-mapping>
        <servlet-name>Log4JTestServlet</servlet-name>
        <url-pattern>/test</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>Log4JTestServlet</servlet-name>
        <servlet-class>com.mucfc.Log4JTestServlet</servlet-class>
    </servlet>
</web-app>

6，tomcat跑起来后访问

http://localhost:8089/test

后台输出

 磁盘上面生成的日志文件