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

 1 package user;
 2 
 3 public class User {
 4     private Integer id;
 5     private String name;
 6     private String password;
 7     private int role;
 8     /**
 9      * @return the id
10      */
11     public Integer getId() {
12         return id;
13     }
14     /**
15      * @param id the id to set
16      */
17     public void setId(Integer id) {
18         this.id = id;
19     }
20     /**
21      * @return the name
22      */
23     public String getName() {
24         return name;
25     }
26     /**
27      * @param name the name to set
28      */
29     public void setName(String name) {
30         this.name = name;
31     }
32     /**
33      * @return the password
34      */
35     public String getPassword() {
36         return password;
37     }
38     /**
39      * @param password the password to set
40      */
41     public void setPassword(String password) {
42         this.password = password;
43     }
44     /**
45      * @return the role
46      */
47     public int getRole() {
48         return role;
49     }
50     /**
51      * @param role the role to set
52      */
53     public void setRole(int role) {
54         this.role = role;
55     }
56     
57 
58 }

DBUtil.java 连接数据库

 1 package util;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.Driver;
 6 import java.sql.SQLException;
 7 import java.sql.Statement;
 8 
 9 public class DBUtil {
10 
11     public static final String driver="com.mysql.jdbc.Driver";
12     public static final String url="jdbc:mysql://localhost:3306/user?characterEncoding=utf8&useSSL=true";
13     public static final String username="root";
14     public static final String password="root";
15     public static Connection con=null;
16 
17 
18     static{
19         try {
20             Class.forName(driver);//得到DriverManager，在下面建立连接时使用
21         } catch (ClassNotFoundException e) {
22             e.printStackTrace();
23         }
24     }
25     
26     public static Connection getCon(){
27         
28         if(con == null){
29             try {
30                 con = DriverManager.getConnection(url, username, password);
31             } catch (SQLException e) {
32                 e.printStackTrace();
33             }            
34         }
35         return con;        
36     }
37     
38     //关闭的方法
39         public static void close(Statement statement,Connection conn){
40                if(statement !=null){
41                    try {
42                     statement.close();
43                 } catch (SQLException e) {
44                     // TODO Auto-generated catch block
45                     e.printStackTrace();
46                 }
47                }
48                
49                if(conn !=null){
50                    try {
51                     conn.close();
52                 } catch (SQLException e) {
53                     // TODO Auto-generated catch block
54                     e.printStackTrace();
55                 }
56                }
57         }
58         
59         public static void main(String args[]){            
60             new DBUtil().getCon();    
61         }
62 }

dao---UserDao.java 处理数据库相关操作

 1 package dao;
 2 
 3 import java.sql.Connection;
 4 import java.sql.PreparedStatement;
 5 import java.sql.ResultSet;
 6 import java.sql.SQLException;
 7 
 8 import user.User;
 9 import util.DBUtil;
10 
11 public class UserDao {
12 
13     //数据库连接对象
14     public  User  login(String username,String password) {
15        User u=null;
16        Connection connection =null;
17        PreparedStatement pstmt=null;
18        ResultSet resultSet=null;
19  
20       //赋值
21       try {
22          connection=DBUtil.getCon();
23           //静态sql语句
24          String sql = "select * from user where name=? and password=?"; 
25          pstmt = (PreparedStatement) connection.prepareStatement(sql);
26          pstmt.setString(1, username);
27          pstmt.setString(2, password);  
28          resultSet = pstmt.executeQuery();
29          if(resultSet.next()){
30             u=new User();
31             u.setName(resultSet.getString("name"));
32             u.setPassword(resultSet.getString("password"));
33             System.out.println("登录成功！");
34          }else{
35             System.out.println("用户名或者密码错误！");
36          }  
37       } catch (SQLException e) {
38         e.printStackTrace();
39       }finally {    
40          // DBUtil.close(pstmt, connection);    
41       }
42       return u;
43  
44     }
45     
46     public boolean addUser(User user) {
47         Connection connection = null;
48         PreparedStatement psmt = null;
49         try {
50              connection = DBUtil.getCon();
51              
52              String sql  ="insert into user(id,name,password,role)values(?,?,?,?);";
53              
54              psmt = (PreparedStatement) connection.prepareStatement(sql);
55              
56              //运用实体对象进行参数赋值
57              psmt.setInt(1, user.getId());
58              psmt.setString(2, user.getName());
59              psmt.setString(3,user.getPassword());
60              psmt.setInt(4, user.getRole());
61              psmt.executeUpdate();         
62         } catch (SQLException e) {
63             e.printStackTrace();
64             return false;
65         }finally {
66             //DBUtil.close(psmt, connection);
67         }
68         return true;        
69     }
70 }

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

 1 package servlet;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.ServletException;
 6 import javax.servlet.annotation.WebServlet;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 import javax.servlet.http.HttpSession;
11 
12 import dao.UserDao;
13 import user.User;
14 
15 /**
16  * Servlet implementation class LoginServlet
17  */
18 @WebServlet("/LoginServlet")
19 public class LoginServlet extends HttpServlet {
20     private static final long serialVersionUID = 1L;
21        
22     /**
23      * @see HttpServlet#HttpServlet()
24      */
25     public LoginServlet() {
26         super();
27         // TODO Auto-generated constructor stub
28     }
29 
30     /**
31      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
32      */
33     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
34         // TODO Auto-generated method stub
35         response.getWriter().append("Served at: ").append(request.getContextPath());
36     }
37 
38     /**
39      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
40      */
41     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
42         // TODO Auto-generated method stub
43         request.setCharacterEncoding("utf-8");
44         response.setContentType("text/html;charset=utf-8");
45         HttpSession sessionzxl = request.getSession();
46         String username = request.getParameter("username");
47         String password = request.getParameter("password");
48         UserDao userDAO=new UserDao(); 
49         User user=userDAO.login(username, password);
50         if(user!=null){
51             sessionzxl.setAttribute("user", user);
52             request.getRequestDispatcher("success.jsp").forward(request, response);;
53         }else{
54             request.getRequestDispatcher("error.jsp").forward(request, response);
55         }
56     }
57 
58 }

 1 package servlet;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.ServletException;
 6 import javax.servlet.annotation.WebServlet;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 import javax.servlet.http.HttpSession;
11 
12 import dao.UserDao;
13 import user.User;
14 
15 /**
16  * Servlet implementation class RegisterServlet
17  */
18 @WebServlet("/RegisterServlet")
19 public class RegisterServlet extends HttpServlet {
20     private static final long serialVersionUID = 1L;
21        
22     /**
23      * @see HttpServlet#HttpServlet()
24      */
25     public RegisterServlet() {
26         super();
27         // TODO Auto-generated constructor stub
28     }
29 
30     /**
31      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
32      */
33     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
34         // TODO Auto-generated method stub
35         response.getWriter().append("Served at: ").append(request.getContextPath());
36     }
37 
38     /**
39      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
40      */
41     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
42         request.setCharacterEncoding("utf-8");
43         response.setContentType("text/html;charset=utf-8");    
44         request.setCharacterEncoding("utf-8");  
45          int id=Integer.valueOf(request.getParameter("id"));  
46          String name=request.getParameter("name");  
47          String password=request.getParameter("password");
48          int role=Integer.valueOf(request.getParameter("role"));
49          User user=new User();
50          user.setId(id);
51          user.setName(name);
52          user.setPassword(password);
53          user.setRole(role);
54          UserDao userDAO=new UserDao(); 
55          boolean result = userDAO.addUser(user);
56          if(result){
57              System.out.println("注册成功！");
58              HttpSession session = request.getSession();
59              session.setAttribute("user", user);
60              String loginSuccess = "LoginSuccess.jsp";
61              response.sendRedirect(loginSuccess);
62          }else{
63              System.out.println("注册失败！");
64              String loginFail = "LoginFail.jsp";
65              response.sendRedirect(loginFail);
66          }         
67          //request.getRequestDispatcher("Login.jsp").forward(request, response);    
68     }
69 }

下面是jsp脚本控制：

首先看一下登录脚本Login.jsp

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 7 <title>登录界面</title>
 8  <style type="text/css">
 9      body{
10          background-image:url(images/login.jpg);
11          background-position:center;
12             background-repeat:no-repeat;
13        }     
14  </style>
15 
16 </head>
17 <body>
18   <div style="text-align:center;margin-top:120px">  
19     <h2>诗远的主页</h2>  
20     <form action="LoginServlet" method="post">  
21         <table style="margin-left:40%">  
22              <marquee width="200"scrolldelay="250">用户登录</marquee> 
23             <tr>  
24                 <td>登录名：</td>  
25                 <td><input name="username" type="text" size="21"></td>  
26             </tr>  
27             <tr>  
28                 <td>密码:</td>  
29                 <td><input name="password" type="password" size="21"></td>  
30             </tr>
31         </table>   
32         <input type="submit" value="登录">  
33         <input type="reset" value="重置">   
34     </form>  
35     <br>  
36     <a href="Register.jsp">注册</a>  
37     </div>  
38 </body>
39 </html>

注册页面Register.jsp

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 7 <title>注册界面</title>
 8     <style type="text/css">
 9      body{
10          background-image:url(images/register.jpg);
11          background-position:center;
12         background-repeat:no-repeat;
13      }     
14  </style>
15 
16 </head>
17 <body>
18 <div style="text-align:center;margin-top:120px">  
19     <h1 >请注册</h1>  
20     <form action="RegisterServlet" method="post">  
21         <table style="margin-left:40%">  
22             <caption>用户注册</caption>  
23             <tr>  
24                 <td>ID:</td>  
25                 <td><input name="id" type="text" size="20"></td>  
26             </tr>  
27             <tr>  
28                 <td>登录名：</td>  
29                 <td><input name="name" type="text" size="20"></td>  
30             </tr>  
31             <tr>  
32                 <td>密码:</td>  
33                 <td><input name="password" type="password" size="20"></td>  
34             </tr>  
35              <tr>  
36                 <td>角色:</td>  
37                 <td><input name="role" type="text" size="20"></td>  
38             </tr>  
39         </table>   
40         <input type="submit" value="注册">  
41         <input type="reset" value="重置">   
42     </form>  
43     <br>  
44     <a href="Login.jsp">登录</a>  
45     </div>  
46 </body>
47 </html>

登录成功界面，这个比较简单，是后面自己修改的success.jsp:

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <%@ page import="user.User"%>
 5 
 6 <%
 7 String path = request.getContextPath();
 8 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 9 %>
10 
11 <html>
12 <head>
13 <base href="<%=basePath%>">
14 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
15 <title>My JSP 'success.jsp' starting page</title>
16 </head>
17 <body>
18 <%User user = (User)session.getAttribute("user");%>
19 "Congratulations! Login success!";<br>
20 username:<%= user.getName()%> <br>
21 password:<%= user.getPassword() %> <br>
22 basePath: <%=basePath%><br>
23 path:<%=path%><br>
24 </body>
25 </html>

登录失败后的界面error.jsp：

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <html>
10 <head>
11 <base href="<%=basePath%>">
12 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
13 <title>My JSP 'fail.jsp' starting page</title>
14 </head>
15 <body>
16     Login Failed! <br>
17     basePath: <%=basePath%><br>
18     path:<%=path%><br>
19     <a href="Login.jsp">请重新登录</a>  
20 </body>
21 </html>

注册成功后的界面LoginSuccess.jsp：

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <%@ page import="user.User"%>
 5 
 6 <%
 7 String path = request.getContextPath();
 8 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 9 %>
10 
11 <html>
12 <head>
13 <base href="<%=basePath%>">
14 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
15 <title>My JSP 'Loginsuccess.jsp' starting page</title>
16 </head>
17 <body>
18 <%User user = (User)session.getAttribute("user");%>
19 "Congratulations! Register success!";<br>
20 username:<%= user.getName()%> <br>
21 password:<%= user.getPassword() %> <br>
22 basePath: <%=basePath%><br>
23 path:<%=path%><br>
24 <a href="Login.jsp">点击登录</a>  
25 </body>
26 </html>

注册失败后的界面LoginFail.jsp

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <html>
10 <head>
11 <base href="<%=basePath%>">
12 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
13 <title>My JSP 'LoginFail.jsp' starting page</title>
14 </head>
15 <body>
16     Register Failed! <br>
17     basePath: <%=basePath%><br>
18     path:<%=path%><br>
19     <a href="Register.jsp">重新注册</a> 
20 </body>
21 </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：

1 <?xml version="1.0" encoding="UTF-8"?>
2 <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">
3   <display-name>ServletWebDemo</display-name>
4   <welcome-file-list>
5     <welcome-file>Login.jsp</welcome-file>
6   </welcome-file-list>
7 </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

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