Sevlet局部变量初始化

时间：2024-09-14 12:33:56
//java 代码部分
package com.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 {

　　　　　//登录窗口

	private static final long serialVersionUID = 1L;

	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.getRequestURL()+"' method='post'>");

		out.println("帐号：<input type='text' name='username' style='width:200px'><br/>");

		out.println("密码：<input type='password' name='password' style'width:200px'>");

		out.println("<input type='submit' value='登录'> </form>");

		out.println("  </BODY>");

		out.println("</HTML>");

		out.flush();

		out.close();

	}
        //验证正确后跳转notice.jsp 登录失败后执行this.doGet（）方法

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		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>");

		String username=request.getParameter("username");

		String password=request.getParameter("password");

		Enumeration params=this.getInitParameterNames();

		while(params.hasMoreElements()){

			String usernameParam=(String)params.nextElement();

			String passwordParam=getInitParameter(usernameParam);

			if(usernameParam.equalsIgnoreCase(usernameParam) && passwordParam.equalsIgnoreCase(password)){

				request.getRequestDispatcher("/WEB-INF/notice.jsp").forward(request, response);//前往

				return;

			}

		}

		this.doGet(request, response);

	}

}

web.xml部分

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

    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_2_5.xsd">

  <display-name></display-name>

  <servlet>

    <servlet-name>InitParamServlet</servlet-name>

    <servlet-class>com.servlet.InitParamServlet</servlet-class>

     <init-param>

        <param-name>user1</param-name>

        <param-value>123</param-value>

    </init-param>

       <init-param>

        <param-name>user2</param-name>

        <param-value>123</param-value>

    </init-param>

    <load-on-startup>0</load-on-startup>

  </servlet>

  <servlet-mapping>

    <servlet-name>InitParamServlet</servlet-name>

    <url-pattern>/servlet/InitParamServlet</url-pattern>

  </servlet-mapping>

  <welcome-file-list>

    <welcome-file>index.jsp</welcome-file>

  </welcome-file-list>

</web-app>

核心代码讲解：

Enumeration params=this.getInitParameterNames();//获取web.xml中设置的全部初始值
params.hasMoreElements()//遍历params

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