JavaWeb入门案例-集合Servlet、tomcat、数据库连接池技术（idea版）

昨天晚上睡觉前暗自告诉自己明天一定要去写这篇感人的javaweb入门笔记（一个小型的用户登录案例的入门笔记）。
enmmmm Flag不能倒！！

首先我们来了解一下在idea中创建一个JavaApplication，各文件夹代表的都是什么意思。详见如图。

1.项目部署

通俗理解：一个项目是需要部署到服务器上，用户才能通过url访问服务器，得到服务器返回的一系列消息。用户发送请求给tomcat服务器，tomcat服务器自动从webapps目录下找所创建的项目下访问的html

常见系统架构：C/S B/S
常见服务器：Tomcat、jetty(淘宝，运行效率比Tomcat高)、resin（新浪，所有开源服务器软件中，运行效率最高的），由于Tomcat免费，所以我们学生党学习就用这个足够。

• 手动部署

  在本地装上tomcat,并在系统环境变量配置好classpath后，打开tomcat目录，将项目部署在webapps下。
  
  webapps->创建的项目->web_INF(自己创建的类)和index.html
  
  webapps目录总结见下图。
  

• idea配置tomcat实现自动部署

1. idea集成tomcat 按照图示1234操作

2. 项目与tomcat关联

第5步是系统自动生成的项目访问名称，自己可根据项目实际情况更改名称。但这里后缀_exploded表示开发版，表示开发者不断升级自己的程序不断添加新功能，尚未将项目集成的war包放在tomcat的webapps下，官方名词将这一过程称为热部署。用户可以通过http://localhost:8080/02Servlet_war_exploded/XX.html访问自己创建的项目。

2.项目构成

Dao：主要实现数据库的增删改查方法；
entity：实体类，创建getter、setter方法，toString方法；
service：控制逻辑层，实现整个逻辑，开启事务，将dao层数据库中的数据与servlet浏览器得到的数据进行比较；
servlet：主要是实现HttpServlet类中的doGet、doPost方法，接受浏览器传过来的数据；
utils：DBUtils类 主要是创建数据连接池，数据库事务操作的接口和方法定义；

• utils包
  utils下的DBUtils.java

package com.qf.servletProject.utils;

import com.alibaba.druid.pool.DruidDataSourceFactory;

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

public class DBUtils {
    public static DataSource ds;
    private static final ThreadLocal<Connection> THREAD_LOCAL = new ThreadLocal<>();

    static{
        Properties pro =new Properties();
        InputStream inputStream=DBUtils.class.getResourceAsStream("/database.properties");


        try {
            pro.load(inputStream);
            //通过DruiDtaSourceFactory创建连接池
            ds= DruidDataSourceFactory.createDataSource(pro);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }

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

    //提交事务
    public static void commit(){
        Connection connection=null;
        try {
            connection=getConnection();
            connection.commit();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            closeAll(connection,null,null);
        }

    }

    public static  void rollback(){
        Connection connection=null;
        try {
            connection=getConnection();
            connection.rollback();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            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 throwables) {
                throwables.printStackTrace();

            }
        }
    }

• servlet包
  servlet下的LoginServlet.java

package com.qf.servletProject.servlet;

import com.qf.servletProject.entity.Admin;
import com.qf.servletProject.service.AdminService;
import com.qf.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;

@WebServlet(value = "/login")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //使接受的数据和发送的数据都是以utf-8的格式
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("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 printWriter=resp.getWriter();
        if(admin!=null){
            //响应给客户端一个结果页面，页面显示登录成功
            printWriter.println("响应显示在浏览器的页面");

        }else{
            printWriter.println("登录账户或密码错误！");
        }
    }

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

    }
}

• service包
  service下的AdminService.java

package com.qf.servletProject.service;

import com.qf.servletProject.entity.Admin;

import java.util.List;

public interface AdminService {
    public Admin login(String username, String password);

    public List<Admin> showAllAdmin();
}

service下的impl包下的AdminServiceImpl.java

package com.qf.servletProject.service.impl;

import com.qf.servletProject.Dao.AdminDao;
import com.qf.servletProject.Dao.impl.AdminDaoImpl;
import com.qf.servletProject.entity.Admin;
import com.qf.servletProject.service.AdminService;
import com.qf.servletProject.utils.DBUtils;

import java.util.List;

public class AdminServiceImpl implements AdminService {
    private AdminDao adminDao=new AdminDaoImpl();

    @Override
    public Admin login(String username, String password) {
        Admin result=null;
        try {
            DBUtils.begin();//开启事务
            Admin admin=adminDao.select(username);
            if(admin!=null){
                if(admin.getPassword().equals(password)){
                    result=admin;
                }
            }
            DBUtils.commit();
        }catch (Exception e){
            DBUtils.rollback();
            e.printStackTrace();
        }
        return result;

    }

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

• entity包
  entity下的Admin

package com.qf.servletProject.entity;

public class Admin {
    private   String username;
    private  String password;
    private   String address;
    private  String phone;


    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 getAddress() {
        return address;
    }

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

    public String getPhone() {
        return phone;
    }

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

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

• Dao包
  Dao下的AdminDao.java

package com.qf.servletProject.Dao;

import com.qf.servletProject.entity.Admin;

import java.util.List;

public interface AdminDao {

    public int insert(Admin admin);
    public int delete(String username);
    public int update(Admin admin);

    public Admin select(String username);
    public List<Admin>  selectAll();


}

Dao下的impl下的AdminDaoImpl.java

package com.qf.servletProject.Dao.impl;

import com.qf.servletProject.Dao.AdminDao;
import com.qf.servletProject.entity.Admin;
import com.qf.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;

public class AdminDaoImpl implements AdminDao {

  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 throwables) {
            throwables.printStackTrace();
        }
        return null;
    }

    @Override
    public List<Admin> selectAll() {
        try {

            List<Admin> admins=queryRunner.query(DBUtils.getConnection(),"select * from admin",new BeanListHandler<Admin>(Admin.class));
            return admins;
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return null;
    }
}

database.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql//localhost:3306//myemployee
username=root
password=123456

initialSize=10
maxActive=20
minIdle=5
maxWait=3000

本文地址：https://blog.csdn.net/kexiaoleqq/article/details/109802846