ServLet+Tomcat编写穷人版登录Web界面

本文中使用到的软件：

Tomcat 8.0
Mysql 5.7
IntelliJ IDEA 2019

项目实现流程：

0. 在数据库中新建如下的数据表：
   

1. IDEA中新建一个项目，选中Web Application：
   

2. 在src文件夹下新建如下所示的文件夹：
   dao： 用于数据库操作
   model： 用于创建web开发需要用到的类
   service： 用于为model类提供服务方法
   Servlet： 用于新建重写Servlet处理Http请求的方法
   Utils： 用于编写一些工具类，例如建立数据库连接的类
   在web文件夹下建立libs文件夹：
   

3. 在Libs文件夹中导入以下两个jar包并右键点击 Add as Library：
   
   

4. 点击右上角的Edit Configuration配置Tomcat
   

5. 点击左上角的加号，选中Tomcat，选择local：
   
   然后需要在Configuration中填入电脑中Tomcat的安装地址：
   
   

设置完成后如果出现Warning就点击Fix一下即可：

然后点击上方的Deployment，清空下方的内容（这部分会导致写出的网页带一个很长的后缀）：

6. 然后就到了我们的编写代码环节了，编写的内容如下：
model.user:

//User.java
public class User {
    private int id;
    private String name;
    private String password;
    private int age;



    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                '}';
    }
}

dao.UserDao:

//UserDao.java
public class UserDao {
    public User selectByName(String name){
        ResultSet rs = null;
        Connection connection = null;
        PreparedStatement pstmt = null;
        DBUtil dbUtil = new DBUtil();
        User user = new User();

        try {
            connection = dbUtil.getConnection();
            pstmt = connection.prepareStatement("select * from user where name=?");
            pstmt.setString(1,name);

            rs = pstmt.executeQuery();
            while(rs.next()){
                user.setId(rs.getInt(1));
                user.setName(rs.getString(2));
                user.setPassword(rs.getString(3));
                user.setAge(rs.getInt(4));
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            dbUtil.closeAll(rs,pstmt,connection);
        }
        return user;
    }

    public boolean InsertUser(String name,String password,int age){
        Connection connection = null;
        PreparedStatement pstmt = null;

        try {
            connection = DBUtil.getConnection();
            pstmt = connection.prepareStatement("insert into user(name,password,age) values (?,?,?)");
            pstmt.setString(1,name);
            pstmt.setString(2,password);
            pstmt.setInt(3,age);

            pstmt.execute();
            return true;
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
}

Service.UserService:

//UserService
public class UserService {
    UserDao userDao = new UserDao();

    //查找用户
    public User SelectByName(String name){
        return userDao.selectByName(name);
    }
    //插入一个新用户
    public boolean Register(String name,String password,int age){
        return userDao.InsertUser(name,password,age);
    }
}

ServLet.LoginServLet

//loginServLet.java
public class LoginServLet extends HttpServlet {
    UserService userService = new UserService();
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    	//如果点击的是登录按钮则获取数据
        String name = req.getParameter("name");
        String password = req.getParameter("password");
        System.out.println("name:"+name);
        User user = userService.SelectByName(name);
        System.out.println(user);
        //验证密码是否正确
        if (password.equals(user.getPassword())) {
            resp.getWriter().write("success");
            System.out.println("success");
        } else {
            resp.getWriter().write("fail");
            System.out.println("fail");
        }

    }
}

ServLet.RegisterServLet:

//RegisterServlet.java
public class RegisterServLet extends HttpServlet {
    UserService userService = new UserService();
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //如果点击了注册按钮则显示如下的HTML页面
        PrintWriter out = resp.getWriter();
        out.write("<html>\n" +
                "  <head>\n" +
                "    <meta http-equiv=\"content-type\" content=\"text/html;charset=gbk\" />\n"+
                "    <title>register</title>\n" +
                "  </head>\n" +
                "  <body>\n" +
                "  <H1>register</H1>\n" +
                "    <form action=\"/register\" method=\"post\">\n" +
                "    name:<input name=\"name\" type=\"text\">\n" +
                "    password:<input name=\"password\" type=\"password\">\n" +
                "    age:<input name=\"age\" type=\"text\">\n"+
                "      <input type=\"submit\" formaction=\"/registerSubmit\" value=\"register\">\n" +
                "    </form>\n" +
                "  </body>\n" +
                "</html>");

    }
}

ServLet.RegisterSubmitServLet:

//RegisterSubmitServLet.java
public class RegisterSubmitServLet extends HttpServlet {
    UserService userService = new UserService();
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    	//获取注册界面数据并插入
        String name = req.getParameter("name");
        String password = req.getParameter("password");
        String age = req.getParameter("age");
        //int age = Integer.parseInt(req.getParameter("age"));
        boolean re = userService.Register(name,password,Integer.valueOf(age));
        System.out.println(name+password+age);
        //String msg = lStrings.getString("http.method_post_not_supported");
        if (re) {
            resp.getWriter().write("success");
        } else {
            resp.getWriter().write("fail");
        }

    }
}

Utils.DBUtil:

//DBUtil.java
public class DBUtil {
    public static Connection connection = null;
    public static Connection getConnection() throws ClassNotFoundException, SQLException {
        if(connection==null) {
            Class.forName("com.mysql.cj.jdbc.Driver");
            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useSSL=false&autoReconnect=true&serverTimezone=GMT", "root", "hxh19981225");
            return connection;
        }else {
            return connection;
        }
    }

    public static void closeAll(ResultSet rs, Statement statement, Connection connection){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(statement!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

7. 接下来还需要编写Web文件夹下的index.jsp以及在WEB-INF中注册编写的ServLet：
   index.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>登录界面</title>
  </head>
  <body>
  <H1>登录界面</H1>
    <form action="/login" method="post">
    name:<input name="name" type="text">
    password:<input name="password" type="password">
    <input type="submit" formaction="/login" value="登录">
      <input type="submit" formaction="/register" value="注册">
    </form>
  </body>
</html>

web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
<!--    登录界面-->
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>com.huxiaoheng.ServLet.LoginServLet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
<!--    注册界面-->
    <servlet>
        <servlet-name>register</servlet-name>
        <servlet-class>com.huxiaoheng.ServLet.RegisterServLet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>register</servlet-name>
        <url-pattern>/register</url-pattern>
    </servlet-mapping>
<!--    注册提交-->
    <servlet>
        <servlet-name>registerSubmit</servlet-name>
        <servlet-class>com.huxiaoheng.ServLet.RegisterSubmitServLet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>registerSubmit</servlet-name>
        <url-pattern>/registerSubmit</url-pattern>
    </servlet-mapping>
</web-app>

这样我们的项目就算完成了，点击运行效果如图所示：

（没有写css，所以长得很抽象）
点击注册显示界面：

注册成功跳转到显示success界面：


可以在数据库查看到该条数据：

然后就可以登录该账号了：

没错因为懒得修改了所以 显示的内容和注册成功是一样的。不过还是可以通过地址看到它们导向的是不一样的地址~~，而且自己所学有限，实在是做不出其他不一样的页面~~
今日的Debug日记：
在写SQL插入语句的时候报错：

查阅之后发现，如果是插入，删除等语句对应的函数一个是execute()而非executeQuery()。另外返回值为一个布尔类型， 而且，不是插入成功就返回True，插入失败返回False。 而是如果第一个结果是 ResultSet 对象，则返回 true；如果第一个结果是更新计数或者没有结果，则返回 false。

好了这差不多是本文的全部内容了，超级简陋的登录界面！

本文地址：https://blog.csdn.net/qq_41823958/article/details/107495396