使用Servlet实现简单的用户管理

怼烎@ 2022-12-01 12:19 113阅读 0赞

##### 一、Servlet作用 #####

> Java Servlet 是运行在 Web 服务器或应用服务器上的程序，它是作为来自 Web 浏览器或其他 HTTP 客户端的请求和 HTTP 服务器上的数据库或应用程序之间的中间层。  
> 使用 Servlet，您可以收集来自网页表单的用户输入，呈现来自数据库或者其他源的记录，还可以动态创建网页。

##### 二、具体实现 #####

文件目录：

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注：idea创建web工程，若想出现meta-inf,如下操作  
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1.注册页面（默认pom.xml已添加依赖）  
暂时采用比较原始的form界面，后续将会使用easy ui 进行美观处理。代码如下：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
    <head>
      <title>login.html</title>
      <style type="text/css">
      </style>
    </head>
    <body>
    <h1>用户登录</h1>
    <form action="http://127.0.0.1:8080/InternshipProject_war/login.emp" method="post">
      用户名：<input type="text" name="userName"><br>
      密码：<input type="password" name="password"><br>
      <input type="submit" value="登录">
    </form>
    <%
      Object obj=request.getAttribute("msg");
      if(obj!=null){ 
    %>
    <span style="color: red;"><%=obj.toString() %></span>
    <%
      }
    %>
    </body>
    </html>

2.创建实体类（注意序列化）  
[序列化原因][Link 1]

package entity;
    
    import java.io.Serializable;
    
    public class Emp implements Serializable { 
      private String name;
      private String sex;
      private String edu;
    
      public Emp() { 
      }
    
      public String getName() { 
        return name;
      }
    
      public void setName(String name) { 
        this.name = name;
      }
    
      public String getSex() { 
        return sex;
      }
    
      public void setSex(String sex) { 
        this.sex = sex;
      }
    
      public String getEdu() { 
        return edu;
      }
    
      public void setEdu(String edu) { 
        this.edu = edu;
      }
    }

3.数据库测试连接  
使用 pom.xml进行导入

<dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>8.0.20</version>
        </dependency>

4.servlet实现

servlet类

package servlets;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.io.UnsupportedEncodingException;
    import java.sql.*;
    import java.text.DateFormat;
    import java.util.Date;
    
    public class EmpServlet extends HttpServlet { 
    
    
      static final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";
      static final String DB_URL = "jdbc:mysql://localhost:8889/emp";//端口号默认3306 ，本人采用集成所以端口号不一样
      static final String USER = "你的用户名";
      static final String PASS = "你的密码";
    
      public  static void main(String[] args) throws SQLException, ClassNotFoundException { 
      }
      protected void doGet(HttpServletRequest request, HttpServletResponse response){ 
    
    
      }
    // post处理
      protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { 
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        String path = request.getServletPath();
        if("/login.emp".equals(path)){ 
          try { 
            login(request,response);
          } catch (SQLException throwables) { 
            throwables.printStackTrace();
          } catch (ClassNotFoundException e) { 
            e.printStackTrace();
          }
        }
    
      }
    
      private  Connection connect() throws ClassNotFoundException, SQLException { 
        Connection conn = null;
        Statement stmt = null;
    
        // 注册JDBC
        Class.forName(JDBC_DRIVER);
        // 打开链接
        System.out.println("连接数据库...");
        conn = DriverManager.getConnection(DB_URL, USER, PASS);
        return conn;
      }
    
    
      // 员工登录
      protected void login(HttpServletRequest request,HttpServletResponse response) throws SQLException, ClassNotFoundException, ServletException, IOException { 
        System.out.println("登录中...");
        String userName =request.getParameter("userName");
        String password =request.getParameter("password");
    
        System.out.println("采集的password:"+password);
        System.out.println("采集的userName:"+userName);
    
        Statement statement = connect().createStatement();
        ResultSet rs = statement.executeQuery("select * from empinfo");
    
        while(rs.next()){ 
    // System.out.println(rs.getString("password"));
          if(password.equals(rs.getString("password"))&&userName.equals(rs.getString("userName"))){ 
            Date date = new Date();
            DateFormat df = DateFormat.getDateInstance(DateFormat.MEDIUM);
            System.out.println(userName+"于"+df.format(date)+"登录成功");
            request.getRequestDispatcher("jsp/index.jsp").forward(request, response);;
            return;
        }
          Date date = new Date();
          DateFormat df = DateFormat.getDateInstance(DateFormat.MEDIUM);
          System.out.println(userName+"于"+df.format(date)+"登录失败");
          // 如果登录失败，控制台输出用户名密码不正确
          System.out.println("用户名密码不正确");
    
    // 将需要转发的信息放入request请求对象中
          request.setAttribute("msg", "用户名密码不正确");
    // 通过请求转发技术将错误信息传递给login.jsp页面做显示
    // 工程内部的资源路径
          request.getRequestDispatcher("/jsp/login/login.jsp").forward(request, response);
        }
      }
    }

web.xml进行配置

<servlet>
        <servlet-name>Emp</servlet-name>
        <servlet-class>servlets.EmpServlet</servlet-class>
      </servlet>
    
      <servlet-mapping>
        <servlet-name>Emp</servlet-name>
        <url-pattern>*.emp</url-pattern>
      </servlet-mapping>

其他：

[request.getRequestDispatcher()和response.sendRedirect()区别][request.getRequestDispatcher_response.sendRedirect]  
[日期的使用][Link 2]

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[Link 1]: https://blog.csdn.net/qq_18298439/article/details/80607057
[request.getRequestDispatcher_response.sendRedirect]: https://www.cnblogs.com/bedbedboy/p/12113125.html
[Link 2]: https://www.cnblogs.com/monjeo/p/9183456.html