Servlet例子

最新推荐文章于 2022-02-21 20:00:07 发布

sunday_code

最新推荐文章于 2022-02-21 20:00:07 发布

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今天没事，就看一下关于基础的 Servlet知识，下面是一个Servlet例子：

package com;

import java.io.IOException;
import java.io.PrintWriter;

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

public class LoginServlet extends HttpServlet{

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
//super.doGet(req, resp);
System.out.println("-------------doget----------");
login(req,resp);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
//super.doPost(req, resp);
System.out.println("-------------dopost----------");
login(req,resp);
}
public void login(HttpServletRequest req,HttpServletResponse resp)throws IOException{
String username=req.getParameter("username");
String password=req.getParameter("password");
resp.setContentType("text/html");
PrintWriter out=resp.getWriter();
out.println("<html><head><title>LOGIN</title></head>");
out.println("<body>username1:"+username+"<br>");
out.println("password1:"+password+"<br></body></html>");
out.flush();

}

@Override
public void service(ServletRequest arg0, ServletResponse arg1)
throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("-------------service---------");
super.service(arg0, arg1);
}

@Override
public void init() throws ServletException {
// TODO Auto-generated method stub
System.out.println("-------------init---------");
super.init();
}

}

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>mylogin</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">


</head>

<body>
<form action="login" method="get">
username:<input type="username" name="username" value=""> <br>
password:<input type="password" name="password" value=""> <br>
<input type="submit" value="submit"> &nasb;
<input type="reset" value="reset"><br>
</form>

</body>
</html>

web.XML配置

<servlet>
<servlet-name>LOGINSERVLET</servlet-name>
<servlet-class>com.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LOGINSERVLET</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>

流程

当点击JSP中的submit后，则按照action对应的相对路径Login找到web.xml文件中<servlet-mapping>的<url-pattern>中的Login，

在根据<servlet-name>为Login找到<servlet>中<servlet-name>为Login的，然后生成一个LoginServlet的实例，

再调用LoginServlet的doGet或者doPost方法，在浏览器上显示结果。

(1) init() 方法 

在 Servlet 的生命期中，仅执行一次 init() 方法。它是在服务器装入 Servlet 时执行的。 可以配置服务器，以在启动服务器或客户机首次访问 Servlet 时装入 Servlet。 无论有多少客户机访问 Servlet，都不会重复执行 init() 。