Servlet：通过初始参数实现权限访问某个文件、页面
目录结构
src 目录下com.xieyuan包MyServlet.java文件（Servlet文件）
package com.xieyuan;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.util.Enumeration;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sun.corba.se.impl.javax.rmi.CORBA.Util;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
public class MyServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public MyServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html");
PrintWriter out=response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println("<HEAD><TITLE>请登录查看NOTICE文件</TITLE></HEAD>");
out.println("<style>body,td,div{font-size:12px;}</style>");
out.println("<BODY>");
String referer=request.getHeader("referer");
//通过获取用户上次进入的页面判断用户是否输入过密码，然后跳转到本页来的
if(referer!=null&&referer.equals(request.getRequestURL().toString()))
out.println("<font color='red'>账号密码错误！</font>");
out.println("<form action='"+request.getRequestURI()+"' method='post'>");
out.println("账号：<input type='text' name='username' autocomplete='off' style='width:200px' /><br/>");
out.println("密码：<input type='password' name='password' style='width:200px' /><br/>");
out.println("<input type='submit' value='登录' />");
out.println("</form>");
//获取上下文参数
out.println("<BR/>"+ this.getServletContext().getInitParameter("test"));
out.println("</BODY");
out.println("</HTML>");
out.flush();
out.close();
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//获得提交的数据
String userName=request.getParameter("username");
String password=request.getParameter("password");
//遍历所有初始参数参数
Enumeration<?> params=this.getInitParameterNames();
while(params.hasMoreElements())
{
String paramName=(String)params.nextElement();
String paramValue=this.getInitParameter(paramName);
if(paramName.equals(userName)&¶mValue.equals(password))
{
/*
* 一个RequestDispatcher对象作为资源在指定的路径，或者为null的包装，
* 如果servlet容器不能返回的RequestDispatcher
*
将请求转发到另一个资源（servlet，JSP和文件或HTML文件）从一个servlet在服务器上。
此方法允许一个servlet做初步处理的请求和其他资源来生成响应。
*/
request.getRequestDispatcher("/WEB-INF/notice.txt").forward(request, response);
return;
}
}
//不匹配，返回
doGet(request, response);
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<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>MyServlet</servlet-name>
<servlet-class>com.xieyuan.MyServlet</servlet-class>
<init-param>
<param-name>user123</param-name>
<param-value>pass123</param-value>
</init-param>
</servlet>
<context-param>
<param-name>test</param-name>
<param-value>这是测试数据！</param-value>
</context-param>
<servlet-mapping>
<servlet-name>MyServlet</servlet-name>
<url-pattern>/servlet/MyServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
部署好WEB后，访问：http://127.0.0.1:8080/Test/servlet/MyServlet 进入登录页面
‘
输入正确的账号：
user123
密码
pass123
访问到预先定义的WEB-INF/notice.txt页面
