Java Web Project自定义错误页面，log4j记录日志。

创建记录日志的文件LoggerHelper.java:

package com.wyp.helper;

import org.apache.log4j.Logger;

public class LoggerHelper {
    private static Logger _logger = Logger.getLogger(LoggerHelper.class);
    private static String newLine = System.getProperty("line.separator");

    public static void info(Logger logger, String message) {
        logger.info(newLine);
        logger.info(message);
    }

    public static void info(Logger logger, String message, Throwable exception) {
        logger.info(newLine);
        logger.info(message, exception);
    }

    public static void debug(Logger logger, String message) {
        logger.debug(newLine);
        logger.debug(message);
    }

    public static void debug(Logger logger, String message, Throwable exception) {
        logger.debug(newLine);
        logger.debug(message, exception);
    }

    public static void error(Logger logger, String message) {
        logger.error(newLine);
        logger.error(message);
    }

    public static void error(Logger logger, String message, Throwable exception) {
        logger.error(newLine);
        logger.error(message, exception);
    }

    public static void info(String message) {
        _logger.info(newLine);
        _logger.info(message);
    }

    public static void info(String message, Throwable exception) {
        _logger.info(newLine);
        _logger.info(message, exception);
    }

    public static void debug(String message) {
        _logger.debug(newLine);
        _logger.debug(message);
    }

    public static void debug(String message, Throwable exception) {
        _logger.debug(newLine);
        _logger.debug(message, exception);
    }

    public static void error(String message) {
        _logger.error(newLine);
        _logger.error(message);
    }

    public static void error(String message, Throwable exception) {
        _logger.error(newLine);
        _logger.error(message, exception);
    }

}

创建Global.java文件：

package helper;

import java.io.File;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;

public class Global implements ServletContextListener {

    private Logger _logger = Logger.getLogger(Global.class);
    
    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
        LoggerHelper.info(_logger, "网站停止");
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
        ServletContext sc = arg0.getServletContext();

        String prefix = sc.getRealPath("/WEB-INF");
        String file = "log4j.properties";
        String configPath = prefix + File.separator + file;

        String logFilePath = sc.getRealPath("/");
        System.setProperty("tomcat", logFilePath);

        PropertyConfigurator.configure(configPath);

        LoggerHelper.info(_logger, "网站启动");
    }
}

web.xml的配置很简单啦，网上搜一下就一大堆了。

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <display-name>JspLog4j</display-name>
    <listener>
        <listener-class>helper.Global</listener-class>
    </listener>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
    <error-page>
        <error-code>500</error-code>
        <location>/error.jsp</location>
    </error-page>
</web-app>

自定义错误页面error.jsp。

<%@page import="com.wyp.helper.LoggerHelper"%>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" isErrorPage="true"%>
<%
    response.setStatus(200);
    String newLine = System.getProperty("line.separator");
    StringBuilder sb = new StringBuilder();
    sb.append(newLine);
    sb.append("访问的路径：");
    sb.append(newLine);
    sb.append(request.getRequestURI());
    sb.append(newLine);
    sb.append("异常信息：");
    sb.append(newLine);
    sb.append(exception.getClass() + " : " + exception.getMessage());
    
    Map<String,String[]> map = request.getParameterMap();
    if (map.size()>0) {
        sb.append(newLine);
        sb.append("请求参数：");
        sb.append(newLine);
        for(Map.Entry<String,String[]> entry : map.entrySet()){
            String key = entry.getKey();
            String[] values = entry.getValue();
            sb.append(key+"=");
            for(String value : values){
                sb.append(value+",");
            }
        }
        sb.append(newLine);
    }
    LoggerHelper.error(sb.toString(),exception);

%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>自定义错误页面</title>
  </head>
  <body>
    <h1>自定义错误页面</h1>
  </body>
</html>

在WEB-INF文件夹里创建log4j.properties文件

log4j.rootLogger=debug,stdout,logfile

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.err
log4j.appender.stdout.layout=org.apache.log4j.SimpleLayout

log4j.appender.logfile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.logfile.File=${tomcat}/logs/website.txt
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.DatePattern='.'yyyy-MM-dd
log4j.appender.logfile.layout.ConversionPattern=%n%d{yyyy-MM-dd HH\:mm\:ss} %F %m

默认日志文件存放在：apache-tomcat-6.0.36\bin\下面，可以使用占位符变量表示你日志信息存放的目录，例如：${tomcat}。

使用System.setProperty("tomcat",sc.getRealPath("/"));设置最终的目录。

最后如果部属目录没有log4j.properties和log4j.jar文件，需要手动将这个log4j.properties文件复制到Tomcat\webapps\项目名\WEB-INF文件夹里，将log4j.jar文件复制到对应的Tomcat\webapps\项目名\WEB-INF\lib目录下面。