JavaNote 3.9 Servlet

一、Servlet

1、每个Servlet对象都有一个ServletConfig对象与之对应

2、ServletConfig对象在多个Servlet之间是不能共享的

3、ServletContext是域对象，在不同资源之间共享数据的

二、连接数据库示例

package com.test;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

@WebServlet(name = "Servlet_2",urlPatterns = "/getResourse")
public class Servlet_2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        InputStream resourceAsStream = this.getServletContext().getResourceAsStream("/db.properties.properties");
        Properties properties = new Properties();
        properties.load(resourceAsStream);
        String root = properties.getProperty("root");
        String url = properties.getProperty("url");
        String password = properties.getProperty("password");
        System.out.println(root);
        System.out.println(url);
        System.out.println(password);
    }
}

三、登录简单示例

1、Servlet

package com.test;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "Servlet_3",urlPatterns = "/login")
public class Servlet_3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            String name = "wuxiaowei";
            String pawd ="123456";
            String username = request.getParameter("name");
            String userpwd = request.getParameter("pwd");
            if(!username.equals(name)){
                request.setAttribute("errormessage","账户错误");
                request.getRequestDispatcher("/loginerror.jsp").forward(request,response);
            }
            else if(!userpwd.equals(pawd)){
                request.setAttribute("errormessage","密码错误");
                request.getRequestDispatcher("/loginerror.jsp").forward(request,response);
            }
             else{                //重定向的两种方式
//                response.setStatus(302);
//                response.setHeader("location","http://www.baidu.com");
                response.sendRedirect(".loginSucess.html");
            }
    }
}

2、html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h2>用户登录</h2>
<form action="login" method="get">
        <p>账号：<input type="text" name="name"/></p>
        <p>密码：<input type="text" name="pwd"/></p>
        <input type="submit" value="登录">
</form>

</body>
</html>

3、loginerror.jsp

<body>
<h2>error</h2>
<div>
    <%=request.getAttribute("errormessage")%>
</div>
</body>