Eclipse+Servlet+jsp+MySql

一、JSP和Servlet的简单介绍：

　　Java开发Web应用程序时用到的技术主要有两种，即Servlet和JSP，Servlet是在服务器端执行的Java程序，一个被称为Servlet容器的程序（其实就是服务器） 负责执行Java程序，而JSP(Java Server Page)则是一个页面， 由JSP容器负责执行。

Servlet以Java程序为主， 输出HTML代码时需要使用out.println函数，也就是说Java中内嵌HTML； 而JSP则以HTML页面为主，需要写Java代码时则在页面中直接插入Java代码， 即HTML中内嵌Java。

MVC模型

MVC模型就是将数据、逻辑处理、用户界面分离的一种方法。

1）、M(Model， 模型)：用于数据处理、逻辑处理

2）、V(View，视图)：用于显示用户界面

3）、C(Controller，控制器)：根据客户端的请求控制逻辑走向和画面

而在Java中，MVC这三个部分则分别对应于 JavaBeans、JSP和Servlet

1）、M = JavaBeans：用于传递数据，拥有与数据相关的逻辑处理

2）、V = JSP：从Model接收数据并生成HTML

3）、C = Servlet：接收HTTP请求并控制Model和View

web的运行机制：

数据首先在jsp上被展示出来，用户看到页面后触发一些事件，并可能传递数据，这些数据和请求被控制器接收到，然后开始处理（往往会需要有一些数据库的操作（查询，修改数据库数据）），当这些处理结束后，我们就需要将数据反馈到JSP上显示给用户看，完成一次完整的交互过程。

下面描述这个例子， 用的Tomcat7.0， mysql用的是5.17版本，下面是工程结构：

Util---DBUtil.java用来连接JDBC数据库

user---User用来定义用户数据类型

servlet---用来处理用户业务求情和逻辑控制

dao---UserDao用来处理与数据库相关的操作，例如添加用户、查找用户等

大家看一下运行效果：

下面描述详细code:

User.Java

 package user;

 public class User {
     private Integer id;
     private String name;
     private String password;
     private int role;
     /**
      * @return the id
      */
     public Integer getId() {
         return id;
     }
     /**
      * @param id the id to set
      */
     public void setId(Integer id) {
         this.id = id;
     }
     /**
      * @return the name
      */
     public String getName() {
         return name;
     }
     /**
      * @param name the name to set
      */
     public void setName(String name) {
         this.name = name;
     }
     /**
      * @return the password
      */
     public String getPassword() {
         return password;
     }
     /**
      * @param password the password to set
      */
     public void setPassword(String password) {
         this.password = password;
     }
     /**
      * @return the role
      */
     public int getRole() {
         return role;
     }
     /**
      * @param role the role to set
      */
     public void setRole(int role) {
         this.role = role;
     }

 }

DBUtil.java  连接数据库

 package util;

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.Driver;
 import java.sql.SQLException;
 import java.sql.Statement;

 public class DBUtil {

     public static final String driver="com.mysql.jdbc.Driver";
     public static final String url="jdbc:mysql://localhost:3306/user?characterEncoding=utf8&useSSL=true";
     public static final String username="root";
     public static final String password="root";
     public static Connection con=null;

     static{
         try {
             Class.forName(driver);//得到DriverManager，在下面建立连接时使用
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         }
     }

     public static Connection getCon(){

         if(con == null){
             try {
                 con = DriverManager.getConnection(url, username, password);
             } catch (SQLException e) {
                 e.printStackTrace();
             }
         }
         return con;
     }

     //关闭的方法
         public static void close(Statement statement,Connection conn){
                if(statement !=null){
                    try {
                     statement.close();
                 } catch (SQLException e) {
                     // TODO Auto-generated catch block
                     e.printStackTrace();
                 }
                }

                if(conn !=null){
                    try {
                     conn.close();
                 } catch (SQLException e) {
                     // TODO Auto-generated catch block
                     e.printStackTrace();
                 }
                }
         }

         public static void main(String args[]){
             new DBUtil().getCon();
         }
 }

dao---UserDao.java   处理数据库相关操作

 package dao;

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 import user.User;
 import util.DBUtil;

 public class UserDao {

     //数据库连接对象
     public  User  login(String username,String password) {
        User u=null;
        Connection connection =null;
        PreparedStatement pstmt=null;
        ResultSet resultSet=null;

       //赋值
       try {
          connection=DBUtil.getCon();
           //静态sql语句
          String sql = "select * from user where name=? and password=?";
          pstmt = (PreparedStatement) connection.prepareStatement(sql);
          pstmt.setString(1, username);
          pstmt.setString(2, password);
          resultSet = pstmt.executeQuery();
          if(resultSet.next()){
             u=new User();
             u.setName(resultSet.getString("name"));
             u.setPassword(resultSet.getString("password"));
             System.out.println("登录成功！");
          }else{
             System.out.println("用户名或者密码错误！");
          }
       } catch (SQLException e) {
         e.printStackTrace();
       }finally {
          // DBUtil.close(pstmt, connection);
       }
       return u;

     }

     public boolean addUser(User user) {
         Connection connection = null;
         PreparedStatement psmt = null;
         try {
              connection = DBUtil.getCon();

              String sql  ="insert into user(id,name,password,role)values(?,?,?,?);";

              psmt = (PreparedStatement) connection.prepareStatement(sql);

              //运用实体对象进行参数赋值
              psmt.setInt(1, user.getId());
              psmt.setString(2, user.getName());
              psmt.setString(3,user.getPassword());
              psmt.setInt(4, user.getRole());
              psmt.executeUpdate();
         } catch (SQLException e) {
             e.printStackTrace();
             return false;
         }finally {
             //DBUtil.close(psmt, connection);
         }
         return true;
     }
 }

Servlet---处理相关用户业务逻辑  LoginServlet和RegisterServlet.java

 package servlet;

 import java.io.IOException;

 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 javax.servlet.http.HttpSession;

 import dao.UserDao;
 import user.User;

 /**
  * Servlet implementation class LoginServlet
  */
 @WebServlet("/LoginServlet")
 public class LoginServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;

     /**
      * @see HttpServlet#HttpServlet()
      */
     public LoginServlet() {
         super();
         // TODO Auto-generated constructor stub
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         response.getWriter().append("Served at: ").append(request.getContextPath());
     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         request.setCharacterEncoding("utf-8");
         response.setContentType("text/html;charset=utf-8");
         HttpSession sessionzxl = request.getSession();
         String username = request.getParameter("username");
         String password = request.getParameter("password");
         UserDao userDAO=new UserDao();
         User user=userDAO.login(username, password);
         if(user!=null){
             sessionzxl.setAttribute("user", user);
             request.getRequestDispatcher("success.jsp").forward(request, response);;
         }else{
             request.getRequestDispatcher("error.jsp").forward(request, response);
         }
     }

 }

 package servlet;

 import java.io.IOException;

 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 javax.servlet.http.HttpSession;

 import dao.UserDao;
 import user.User;

 /**
  * Servlet implementation class RegisterServlet
  */
 @WebServlet("/RegisterServlet")
 public class RegisterServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;

     /**
      * @see HttpServlet#HttpServlet()
      */
     public RegisterServlet() {
         super();
         // TODO Auto-generated constructor stub
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         response.getWriter().append("Served at: ").append(request.getContextPath());
     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         request.setCharacterEncoding("utf-8");
         response.setContentType("text/html;charset=utf-8");
         request.setCharacterEncoding("utf-8");
          int id=Integer.valueOf(request.getParameter("id"));
          String name=request.getParameter("name");
          String password=request.getParameter("password");
          int role=Integer.valueOf(request.getParameter("role"));
          User user=new User();
          user.setId(id);
          user.setName(name);
          user.setPassword(password);
          user.setRole(role);
          UserDao userDAO=new UserDao();
          boolean result = userDAO.addUser(user);
          if(result){
              System.out.println("注册成功！");
              HttpSession session = request.getSession();
              session.setAttribute("user", user);
              String loginSuccess = "LoginSuccess.jsp";
              response.sendRedirect(loginSuccess);
          }else{
              System.out.println("注册失败！");
              String loginFail = "LoginFail.jsp";
              response.sendRedirect(loginFail);
          }
          //request.getRequestDispatcher("Login.jsp").forward(request, response);
     }
 }

下面是jsp脚本控制：

首先看一下登录脚本Login.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>登录界面</title>
  <style type="text/css">
      body{
          background-image:url(images/login.jpg);
          background-position:center;
             background-repeat:no-repeat;
        }
  </style>

 </head>
 <body>
   <div style="text-align:center;margin-top:120px">
     <h2>诗远的主页</h2>
     <form action="LoginServlet" method="post">
         <table style="margin-left:40%">
              <marquee width="200"scrolldelay="250">用户登录</marquee>
             <tr>
                 <td>登录名：</td>
                 <td><input name="username" type="text" size="21"></td>
             </tr>
             <tr>
                 <td>密码:</td>
                 <td><input name="password" type="password" size="21"></td>
             </tr>
         </table>
         <input type="submit" value="登录">
         <input type="reset" value="重置">
     </form>
     <br>
     <a href="Register.jsp">注册</a>
     </div>
 </body>
 </html>

注册页面Register.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>注册界面</title>
     <style type="text/css">
      body{
          background-image:url(images/register.jpg);
          background-position:center;
         background-repeat:no-repeat;
      }
  </style>

 </head>
 <body>
 <div style="text-align:center;margin-top:120px">
     <h1 >请注册</h1>
     <form action="RegisterServlet" method="post">
         <table style="margin-left:40%">
             <caption>用户注册</caption>
             <tr>
                 <td>ID:</td>
                 <td><input name="id" type="text" size="20"></td>
             </tr>
             <tr>
                 <td>登录名：</td>
                 <td><input name="name" type="text" size="20"></td>
             </tr>
             <tr>
                 <td>密码:</td>
                 <td><input name="password" type="password" size="20"></td>
             </tr>
              <tr>
                 <td>角色:</td>
                 <td><input name="role" type="text" size="20"></td>
             </tr>
         </table>
         <input type="submit" value="注册">
         <input type="reset" value="重置">
     </form>
     <br>
     <a href="Login.jsp">登录</a>
     </div>
 </body>
 </html>

登录成功界面，这个比较简单，是后面自己修改的success.jsp:

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <%@ page import="user.User"%>

 <%
 String path = request.getContextPath();
 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 %>

 <html>
 <head>
 <base href="<%=basePath%>">
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>My JSP 'success.jsp' starting page</title>
 </head>
 <body>
 <%User user = (User)session.getAttribute("user");%>
 "Congratulations! Login success!";<br>
 username:<%= user.getName()%> <br>
 password:<%= user.getPassword() %> <br>
 basePath: <%=basePath%><br>
 path:<%=path%><br>
 </body>
 </html>

登录失败后的界面error.jsp：

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <%
 String path = request.getContextPath();
 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 %>

 <html>
 <head>
 <base href="<%=basePath%>">
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>My JSP 'fail.jsp' starting page</title>
 </head>
 <body>
     Login Failed! <br>
     basePath: <%=basePath%><br>
     path:<%=path%><br>
     <a href="Login.jsp">请重新登录</a>
 </body>
 </html>

注册成功后的界面LoginSuccess.jsp：

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <%@ page import="user.User"%>

 <%
 String path = request.getContextPath();
 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 %>

 <html>
 <head>
 <base href="<%=basePath%>">
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>My JSP 'Loginsuccess.jsp' starting page</title>
 </head>
 <body>
 <%User user = (User)session.getAttribute("user");%>
 "Congratulations! Register success!";<br>
 username:<%= user.getName()%> <br>
 password:<%= user.getPassword() %> <br>
 basePath: <%=basePath%><br>
 path:<%=path%><br>
 <a href="Login.jsp">点击登录</a>
 </body>
 </html>

注册失败后的界面LoginFail.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <%
 String path = request.getContextPath();
 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 %>

 <html>
 <head>
 <base href="<%=basePath%>">
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>My JSP 'LoginFail.jsp' starting page</title>
 </head>
 <body>
     Register Failed! <br>
     basePath: <%=basePath%><br>
     path:<%=path%><br>
     <a href="Register.jsp">重新注册</a>
 </body>
 </html>

所有的jsp脚本到此结束。

下面看web.xml配置：如果是比较旧的tomcat版本，不支持WebServlet注解方式，就需要在web.xml里面配置servlet-mapping映射。

我用的是Tomcat7.0，Servlet是3.0， 支持servlet注解。所以不需要在web.xml里面配置servlet.你可以在Servlet的java文件里面看到这样自动生成的注解：

@WebServlet("/LoginServlet")

@WebServlet("/RegisterServlet")

但是在web.xml里面需要在webclme-file-list配置登录界面，如下：

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
   <display-name>ServletWebDemo</display-name>
   <welcome-file-list>
     <welcome-file>Login.jsp</welcome-file>
   </welcome-file-list>
 </web-app>

最后看一下数据库操作，我装的是Mysql5.7版本，装过最新的Mysql8.15版本，可是装不成功，所以直接装的5.7版本。然后还装了一个SQLyog软件来界面控制SQL。

从DBUtil里面可以看到，连接的数据库是user, 后面在UserDao操作的数据表是user。mysql登录用户名和密码是root和root。下面接了个Mysql的数据结构：

在上面数据表定义中，把id声明为主键，下面是我注册过几次后数据表的结构，

注意一下，在上面工程中要导入两个包，一个是servlet-api.jar， 一个是mysql-connector-java-5.1.47.jar

背景图片放在：images下面。到此整个工程code介绍完了。按照上面code应该是能够运行起来。

主要参考博客有：

https://blog.csdn.net/yjx568135132/article/details/73896240

https://blog.csdn.net/blackplus28/article/details/80603863