web入门案例

简述

　　下面我们来构建一个小型web项目，实现登录功能和展示所有用户功能。

步骤

　　首先我们来创建个数据库叫companydb，创建个表叫admin设置字段及类型

CREATE DATABASE companydb;
USE companydb;
CREATE TABLE admin(
        username VARCHAR(20) PRIMARY KEY NOT NULL,
        PASSWORD VARCHAR(20) NOT NULL,
        phone VARCHAR(11) NOT NULL,
        address VARCHAR(20) NOT NULL
)CHARSET=utf8;

　　然后我们插入数据

INSERT INTO admin VALUES('hjj','123456','12345678901','广外');

　　接着我们创建一个普通的web项目，教程——https://www.cnblogs.com/qq2210446939/p/13922657.html

　　我们导入几个基本的jar包

 　　然后在src目录下创建我们的数据库配置文件，写上驱动用户密码连接池配置等信息

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/companydb?useUnicode=tru&characterEncoding=UTF-8
username=root
password=123456

#初始连接数量
initialSize=10
#最大活动连接数量
maxActive=20
#最小空闲连接数量
minIdle=5
#超时时限
maxWait=3000

　　然后我们创建一个servletProject包，并在里面创建utils包，在包里创建我们的DbUtils工具类

　　工具类方便我们操作和数据库的连接，事务的提交回滚等操作，当然如果我们用mybatis框架的话就不用写，框架帮我们弄好了

package com.hjj.servletProject.utils;

import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/**
 * @author Layton
 * @version 1.0
 * @date 2020/11/20 18:42
 */
public class DbUtils {
    //数据库连接池
    private static DruidDataSource ds;
    //
    private static final ThreadLocal<Connection> THREAD_LOCAL = new ThreadLocal<>();

    static {
        Properties properties = new Properties();
        InputStream inputStream = DbUtils.class.getResourceAsStream("/database.properties");
        try {
            properties.load(inputStream);
            ds = (DruidDataSource) DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        //从连接池里拿连接
        Connection connection = THREAD_LOCAL.get();
        try {
            if (connection == null) {
                //新建连接并放入连接池
                connection = ds.getConnection();
                THREAD_LOCAL.set(connection);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

    /**
     * 开启事务
     */
    public static void begin() {
        Connection connection = null;
        connection = getConnection();
        try {
            connection.setAutoCommit(false);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 提交事务
     */
    public static void commit() {
        Connection connection = null;
        try {
            connection = getConnection();
            connection.commit();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //statement和result参数都为空
            closeAll(connection, null, null);
        }
    }

    public static void rollback() {
        Connection connection = null;
        try {
            connection = getConnection();
            connection.rollback();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //statement和ResultSet参数都为空
            closeAll(connection, null, null);
        }
    }

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

　　接着我们创建一个entity包用来存实体类，里面生成我们的admin实体类

　　我们在admin类中生成构造、get、set、tostring方法

package com.hjj.servletProject.entity;


public class Admin {

    private String username;
    private String password;
    private String phone;
    private String address;

    public Admin() {
    }

    public Admin(String username, String password, String phone, String address) {
        this.username = username;
        this.password = password;
        this.phone = phone;
        this.address = address;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }


    public String getPassword() {
        return password;
    }

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


    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }


    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "Admin{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", phone='" + phone + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}
    

　　接着我们创建一个dao包，表示持久层，在该包创建一个IAdminDao接口

　　里面写上和数据库发生交互的方法，增删查改等

package com.hjj.servletProject.dao;

import com.hjj.servletProject.entity.Admin;

import java.util.List;

public interface IAdminDao {
    //插入
    public int insert(Admin admin);
    //删除
    int delete(String username);
    //更新
    int update(Admin admin);
    //查询一个
    Admin select(String username);
    //查询所有
    List<Admin> selectAll();
}

　　然后我们在dao包里创建一个dao层的实现类，继承IAdminDao接口，通过queryRunner实现我们的查询一个和查询所有方法，增删改这里先不写

package com.hjj.servletProject.dao.impl;

import com.hjj.servletProject.dao.IAdminDao;
import com.hjj.servletProject.entity.Admin;
import com.hjj.servletProject.utils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import java.sql.SQLException;
import java.util.List;

/**
 * @author Layton
 * @version 1.0
 * @date 2020/11/20 19:39
 */
public class IAdminDaoImpl implements IAdminDao {

    private QueryRunner queryRunner = new QueryRunner();

    @Override
    public int insert(Admin admin) {
        return 0;
    }

    @Override
    public int delete(String username) {
        return 0;
    }

    @Override
    public int update(Admin admin) {
        return 0;
    }

    @Override
    public Admin select(String username) {
        try {
            Admin admin = queryRunner.query(DbUtils.getConnection(), "select * from admin where username = ?;", new BeanHandler<Admin>(Admin.class), username);
            return admin;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    public List<Admin> selectAll() {
        List<Admin> admins = null;
        try {
            admins = queryRunner.query(DbUtils.getConnection(),"select * from admin",new BeanListHandler<Admin>(Admin.class));
            return admins;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
}

　　然后我们创建我们的service层，放上我们的AdminServie接口

package com.hjj.servletProject.service;


import com.hjj.servletProject.entity.Admin;

import java.util.List;

/**
 * @author Layton
 * @version 1.0
 * @date 2020/11/21 0:22
 */
public interface AdminService {
    /**
     * 登录
     * @param username
     * @param password
     * @return
     */
    public Admin Login(String username, String password);

    /**
     * 展示所有用户
     * @return
     */
    public List<Admin> showAllAdmin();
}

　　同样的添加service的实现类

　　里面实现我们的登录方法和显示所有用户方法

package com.hjj.servletProject.service.impl;

import com.hjj.servletProject.dao.IAdminDao;
import com.hjj.servletProject.dao.impl.IAdminDaoImpl;
import com.hjj.servletProject.entity.Admin;
import com.hjj.servletProject.service.AdminService;
import com.hjj.servletProject.utils.DbUtils;

import java.util.List;

/**
 * @author Layton
 * @version 1.0
 * @date 2020/11/21 0:28
 */
public class AdminServiceImpl implements AdminService {

    //dao层的接口对象
    private IAdminDao adminDao = new IAdminDaoImpl();

    @Override
    public Admin Login(String username, String password) {
        Admin result = null;
        try {
            //开始事务
            DbUtils.begin();
            Admin admin = adminDao.select(username);
            if (admin != null) {
                //用户存在，接下来验证密码
                if (admin.getPassword().equals(password)) {
                    //查询到的对象密码和传过来的密码相等
                    result = admin;
                }
            }
            //提交事务
            DbUtils.commit();
        } catch (Exception e) {
            e.printStackTrace();
            //出现异常则回滚
            DbUtils.rollback();
        }
        return result;
    }

    @Override
    public List<Admin> showAllAdmin() {
        return null;
    }
}

　　接着我们创建servlet包，在包里创建我们的LoginServlet类继承HttpServlet，同时重写doget、dopost方法完成登录

　　现在我们让doPost调用doGet，在doget里写响应过程

　　分为以下几步：设置字符集、接受参数、调用service层业务、分结果返回页面

package com.hjj.servletProject.servlet;

import com.hjj.servletProject.entity.Admin;
import com.hjj.servletProject.service.AdminService;
import com.hjj.servletProject.service.impl.AdminServiceImpl;

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.PrintWriter;

/**
 * @author Layton
 * @version 1.0
 * @date 2020/11/21 15:36
 */
@WebServlet("/login")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=UTF-8");
        //1.收参
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //2.调用业务逻辑
        AdminService adminService = new AdminServiceImpl();
        Admin admin = adminService.Login(username,password);
        //3.处理结果
        PrintWriter pw = resp.getWriter();
        if(admin != null){
            //响应给客户端一个结果页面，显示登录成功
            pw.println("<html>");
            pw.println("<head>");
            pw.println("<meta charset='UTF-8'>");
            pw.println("<title>结果页面</title>");
            pw.println("</head>");
            pw.println("<body>");
            pw.println("<h1>登录成功</h1>");
            pw.println("</body>");
            pw.println("</html>");
        }else{
            //响应给客户端一个结果页面，显示登录失败
            pw.println("<html>");
            pw.println("<head>");
            pw.println("<meta charset='UTF-8'>");
            pw.println("<title>结果页面</title>");
            pw.println("</head>");
            pw.println("<body>");
            pw.println("<h1>登录失败</h1>");
            pw.println("</body>");
            pw.println("</html>");
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}

　　最后我们在web目录添加个login的html文件，里面写上我们的表单，设置好name以便于传递参数给我们的LoginServlet

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录页面</title>
</head>
<body>
    <form action="/My_Servlet_war_exploded/login" 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>
</body>
</html>

　　至此我们的登录需求已经完成了,我们启动tomcat服务器，在Url里输入login.html就可以跳转到登录界面，输入正确的用户名和密码即可提交到我们的LoginServlet，LoginServlet会接受参数并调用service业务，根据业务结果也就是用户名密码对不对返回不同的结果

 

 　　接着我们实现展示所有用户功能，我们先写业务层逻辑代码

@Override
    public List<Admin> showAllAdmin() {
        List<Admin> admins = null;
        try {
            DbUtils.begin();
            admins = adminDao.selectAll();
            DbUtils.commit();
        } catch (Exception e) {
            e.printStackTrace();
            DbUtils.rollback();
        }
        return admins;
    }

　　需要注意的是，无论有没有查到东西，都会返回一个admins列表

　　接着我们写我们的ShowAllAdminServlet用于展示所有用户，同样的我们重写get和post方法，让post调用get

　　在get里就无需收参了，我们通过业务层拿到admins列表，然后在一个table里遍历admins打印数据,写上注释，路径为showall

package com.hjj.servletProject.servlet;

import com.hjj.servletProject.entity.Admin;
import com.hjj.servletProject.service.AdminService;
import com.hjj.servletProject.service.impl.AdminServiceImpl;

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.PipedWriter;
import java.io.PrintWriter;
import java.util.List;

/**
 * @author Layton
 * @version 1.0
 * @date 2020/11/23 18:36
 */
@WebServlet("/showall")
public class ShowAllAdminServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("123321");
        resp.setContentType("text/html;charset=utf-8");
        AdminService adminService = new AdminServiceImpl();

        List<Admin> admins = adminService.showAllAdmin();
        PrintWriter pw = resp.getWriter();
        if(admins != null){
            pw.println("<html>");
            pw.println("<head>");
            pw.println("<meta charset='UTF-8'>");
            pw.println("<title>显示所有</title>");
            pw.println("</head>");
            pw.println("<body>");

            pw.println("<table>");
            pw.println("    <tr>");
            pw.println("        <td>username</td>");
            pw.println("        <td>password</td>");
            pw.println("        <td>phone</td>");
            pw.println("        <td>address</td>");
            pw.println("    </tr>");
            for(Admin admin: admins){
                pw.println("    <tr>");
                pw.println("        <td>"+admin.getUsername()+"</td>");
                pw.println("        <td>"+admin.getPassword()+"</td>");
                pw.println("        <td>"+admin.getPhone()+"</td>");
                pw.println("        <td>"+admin.getAddress()+"</td>");
                pw.println("    </tr>");
            }
            pw.println("</table>");
            pw.println("</body>");
            pw.println("</html>");
        }else{
            pw.println("<html>");
            pw.println("<head>");
            pw.println("<meta charset='UTF-8>");
            pw.println("<title>显示所有<title>");
            pw.println("</head>");
            pw.println("<body>");
            pw.println("<h3>当前没有用户<h3>");
            pw.println("</body>");
            pw.println("</html>");
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

　　接着我们启动服务器，访问/showall，nice~