1.新建Servlet：
package com.wch.sp.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 RequestServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public RequestServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy();
}
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>請登錄查看祕密文件</TITLE></HEAD>");
out.println(" <BODY>");
out.println(request.getRequestURI());
String requestURI=request.getRequestURI();
out.print("<form action='"+requestURI+"' method='POST'>");
out.print("帳號:<input type='text' name='username' style='width:200px;'/><br/>");
out.print("密碼:<input type='password' name='password' style='width:200px;'/><br/>");
out.println("<input type='submit' value='登錄'>");
out.println("</form>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html");
String username = request.getParameter("username");
String password= request.getParameter("password");
Enumeration params=this.getInitParameterNames();
while(params.hasMoreElements())
{
String usernameParame = params.nextElement().toString();
String passwordParame =this.getInitParameter(usernameParame);
if(username.equals(usernameParame)&&password.equals(passwordParame))
{
request.getRequestDispatcher("/WEB-INF/noticde.html").forward(request, response);
return;
}
}
this.doGet(request, response);
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
2.配置web.xml文件：
<?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">
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<!-- 配置Servlet中，以下兩個屬性是必須配置的，name是可以任意取的，class配置的是包名 -->
<servlet-name>FirstServlet</servlet-name>
<servlet-class>com.wch.sp.servlet.FirstServlet</servlet-class>
<!-- servlet中還有許多可選的配置，例如下面的初始化參數配置，一個Servlet可以配置多個初始化參數，Servlet中可以使用getInitParameter(name)
或者是getInitParameterNames()獲取配置的參數值-->
<init-param>
<param-name>message</param-name>
<param-value>utf-8</param-value>
</init-param>
<!--下面的標籤配置的是Servlet的加載方式，可選值爲0或1，如果配置爲1，Tomcat會在啓動時加載該Serlet。
否則，Tomcat會在有人第一次請求該Servlet的時候才加載該 Servlet。實際項目中，一些框架如Struts、JSF、Spring都是用該參數來加載框架中核心的Servlet-->
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>RequestServlet</servlet-name>
<servlet-class>com.wch.sp.servlet.RequestServlet</servlet-class>
<init-param>
<param-name>admin</param-name>
<param-value>admin</param-value>
</init-param>
<init-param>
<param-name>babyface</param-name>
<param-value>123</param-value>
</init-param>
</servlet>
<!--配置Servlet的訪問方式，Servlet-name就是前面配置的Servlet的名稱，url-pattern配置該Servlet的訪問方式-->
<servlet-mapping>
<servlet-name>FirstServlet</servlet-name>
<!-- 配置的Servlet的訪問路徑，可以隨便設置，比如說我現在訪問Servlet的路徑就是：http://localhost:8080/Servlet/servlet/firstServlet -->
<url-pattern>/servlet/firstServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>RequestServlet</servlet-name>
<url-pattern>/servlet/RequestServlet</url-pattern>
</servlet-mapping>
</web-app>
3.在WEB-INF下面建立noticde.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>noticde.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
</head>
<body>
HELLO
</body>
</html>
4.發佈項目至服務器，啓動服務器，訪問：http://localhost:8080/Servlet/servlet/RequestServlet
結果爲：
登錄後：
總結：
1.在web.xml配置文件中配置Servlet的時候，可以給Servlet配置初始化參數，使用<init-param>標籤類配置。配置完畢之後，Servlet提供方法：getInitParameterNames()或者getInitParameterName（String name）方法獲取初始化參數值。這些初始化參數也可以使用ServletConfig對象獲取，Servlet提供getServletConfig()方法獲取ServletConfig對象。由ServletConfig取初始化參數與Servlet直接取方式一樣。
2.初始化參數的好處就是可以把某些變量拿到web.xml中配置，需要修改時只需要修改web.xml文件中重啓服務器即可，而不是需要修改Servlet類
3.由此擴展到上下文參數(<context-param>)：由於<init-param>是配置在<servlet>標籤裏的，只能由這個Servlet來讀取，因此它不是全局參數，不能被其它的Servlet讀取，這時可以配置上下文參數。獲取context-param可以使用ServletContext對象，Servlet中可以通過getServletConfig（).getServletContext()來獲取一個ServletContext對象，使用ServletContext的getInitParameter()方法來獲取指定名稱的參數，通過getInitParameters（）獲取所有的context-param參數名稱
