web.xml的初始化参数:context

1、初始化参数

web.xml里面可以定义两种参数： (1)application范围内的参数，存放在servletcontext中，在web.xml中配置如下：

context/param

avalible during application

(2)servlet范围内的参数，只能在servlet的init()方法中取得，在web.xml中配置如下：

MainServlet

com.wes.controller.MainServlet

param1

avalible in servlet init()

0

在servlet中可以通过代码分别取用：

package com.wes.controller;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

public

class MainServlet

extends HttpServlet

{ public MainServlet() { super(); } public void init() throws ServletException { System.out.println("下面的参数是存放在servletcontext中的"); System.out.println(getServletContext().getInitParameter("context/param"));

System.out.println("下面的两个参数param1是在servlet中存放的");

System.out.println(this.getInitParameter("param1")); } }

第一种参数在servlet里面可以通过getServletContext().getInitParameter("context/param")得到 第二种参数只能在servlet的init()方法中通过this.getInitParameter("param1")取

2、初始化参数获取

count 1200

loginServlet loginServlet loginServlet loginServlet 系统初始化数 num 100 loginServlet /loginServlet

获取参数的方法以及异同

String username=request.getParameter("username"); response.setCharacterEncoding("gb2312"); System.out.println("getServletContext()："+getServletContext()); ServletContext context=getServletConfig().getServletContext(); String num=context.getInitParameter("num");// 获取不到值 String count=context.getInitParameter("count");// 获取到值 System.out.println("num："+num);//null System.out.println("count："+count);//1200 System.out.println("num："+getServletConfig().getInitParameter("num"));//100获取到值 System.out.println("count："+getServletConfig().getInitParameter("count"));//null获取不到值 System.out.println("request.getSession().getServletContext()："+request.getSession().getServletContext()); request.setAttribute("username", username); PrintWriter out=response.getWriter(); out.println("获取的用户名是："+username);

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1、URL中含有两个问号'?? '的处理

http://a.tbcdn.cn/??s/kissy/1.2.0/kissy-min.js,p/global/1.0/global-min.js,p/fp/2012/core.js,p/fp/2012/fp/module.js,p/fp/2012/fp/util.js,p/fp/2012/fp/directpromo.js?t=2012080620120925.js

解决：先以/*做全匹配，再分配给其余servlet进行处理， url的匹配顺序，参考：http://tianya23.blog.51cto.com/1081650/1001568

@Override

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

throws IOException, ServletException {

HttpServletRequest httpRequest = null;

if (request instanceof HttpServletRequest) {

httpRequest = (HttpServletRequest) request;

} else {

throw new RuntimeException("not http request");

}

String queryString = httpRequest.getQueryString();

if (queryString != null && queryString.startsWith("?")) {

request.getRequestDispatcher("/taobao").forward(httpRequest, response);

} else {

chain.doFilter(httpRequest, response);

}

}

本文转自 tianya23 51CTO博客，原文链接：http://blog.51cto.com/tianya23/1017887，如需转载请自行联系原作者