servlet从xml提取数据登陆

在xml文档下可以设置参数的初始值，在这里把他当成了数据库在用

  <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>InitParamServlet</servlet-name>
    <servlet-class>servlet.InitParamServlet</servlet-class>
    <init-param>
        <param-name>helloween</param-name>
        <param-value>password</param-value>
    </init-param>
        <init-param>
        <param-name>admin</param-name>
        <param-value>admin</param-value>
    </init-param>
        <init-param>
        <param-name>babyface</param-name>
        <param-value>babyface</param-value>
    </init-param>
  </servlet>

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变量名为账号，值为密码

在doGet中的<form>提供的<input type='text' name='username'...>的值

可以传递到doPost

然后用String username=request.getParameter("username");来获取他

再和xml里面的变量比较

原码

package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class InitParamServlet extends HttpServlet {

    /**
     * Constructor of the object.
     */
    public InitParamServlet() {
        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 {
        response.setCharacterEncoding("UTF-8");
        request.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>A Servlet</TITLE></HEAD>");
        out.println("  <BODY>");
        out.println("<form action='"+request.getRequestURI()+"' method='post'>");
        out.println("账号:<input type='text' name='username'<br><br/>");
        out.println("密码:<input type='password' name='password'<br><br/>");
        out.println("<input type='submit' value='  登陆    '>");
        out.println("</form>");
        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 {
        response.setCharacterEncoding("UTF-8");
        request.setCharacterEncoding("UTF-8");

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String username=request.getParameter("username");
        String password=request.getParameter("password");
        Enumeration params=this.getInitParameterNames();
        for(;params.hasMoreElements();){
            String usernameParam=params.nextElement().toString();
            String passnameParam=getInitParameter(usernameParam);
            if(usernameParam.equalsIgnoreCase(username)&&passnameParam.equals(password)){
                request.getRequestDispatcher("/WEB-INF/notice.html").forward(request,response);
                return;
            }
        }
        doGet(request,response);//不匹配的话重新加载
    }

    /**
     * Initialization of the servlet. <br>
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }

}

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