java: three-tier architecture

Three-tier architecture: software design architecture

1. Interface layer (presentation layer): the interface that users see. Users can interact with the server through components on the interface
2. Business logic layer: handles business logic.
3. Data access layer: operates data storage files.
   
   

Example: The simplest addition, deletion, modification and search

1. Requirements: Add, delete, modify and check user information

2. design:

   1. Technology selection: Servlet+JSP+MySQL+JDBCTempleat+Duird+BeanUtilS+tomcat
   2. Database design:
      create database day17; – Create database
      use day17; – Use database
      create table user( – Create table
      id int primary key auto_increment,
      name varchar(20) not null,
      gender varchar(5),
      age int,
      address varchar(32) ),
      qq varchar(20),
      email varchar(50)
      );

3. Development:

   1. Environment setup

      1. Create database environment
      2. Create a project and import the required jar packages

   2. coding

4. test

5. Deployment and operation
   
   
   UserDaoImpl.java

package cn.itcast.dao.impl;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import cn.itcast.util.JDBCUtils;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

import java.util.List;

public class UserDaoImpl implements UserDao {
    
    

    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    @Override
    public List<User> findAll() {
    
    
        //使用JDBC操作数据库...
        //1.定义sql
        String sql = "select * from user";
        List<User> users = template.query(sql, new BeanPropertyRowMapper<User>(User.class));

        return users;
    }
}

UserDao.java

package cn.itcast.dao;

import cn.itcast.domain.User;

import java.util.List;

/**
 * 用户操作的DAO
 */
public interface UserDao {
    
    


    public List<User> findAll();
}

User.java

package cn.itcast.domain;

public class User {
    
    
    private int id;
    private String name;
    private String gender;
    private int age;
    private String address;
    private String qq;
    private String email;

    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 getGender() {
    
    
        return gender;
    }

    public void setGender(String gender) {
    
    
        this.gender = gender;
    }

    public int getAge() {
    
    
        return age;
    }

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

    public String getAddress() {
    
    
        return address;
    }

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

    public String getQq() {
    
    
        return qq;
    }

    public void setQq(String qq) {
    
    
        this.qq = qq;
    }

    public String getEmail() {
    
    
        return email;
    }

    public void setEmail(String email) {
    
    
        this.email = email;
    }

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

UserServiceImpl.java

package cn.itcast.service.impl;

import cn.itcast.dao.UserDao;
import cn.itcast.dao.impl.UserDaoImpl;
import cn.itcast.domain.User;
import cn.itcast.service.UserService;

import java.util.List;

public class UserServiceImpl implements UserService {
    
    
    private UserDao dao = new UserDaoImpl();

    @Override
    public List<User> findAll() {
    
    
        //调用Dao完成查询
        return dao.findAll();
    }
}

UserService.java

package cn.itcast.service;

import cn.itcast.domain.User;

import java.util.List;

/**
 * 用户管理的业务接口
 */
public interface UserService {
    
    

    /**
     * 查询所有用户信息
     * @return
     */
    public List<User> findAll();
}

JDBCUtils.java

package cn.itcast.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

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

/**
 * JDBC工具类 使用Durid连接池
 */
public class JDBCUtils {
    
    

    private static DataSource ds ;

    static {
    
    

        try {
    
    
            //1.加载配置文件
            Properties pro = new Properties();
            //使用ClassLoader加载配置文件，获取字节输入流
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
            pro.load(is);

            //2.初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);

        } catch (IOException e) {
    
    
            e.printStackTrace();
        } catch (Exception e) {
    
    
            e.printStackTrace();
        }
    }

    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
    
    
        return ds;
    }


    /**
     * 获取连接Connection对象
     */
    public static Connection getConnection() throws SQLException {
    
    
        return  ds.getConnection();
    }
}

UserListServlet.java

package cn.itcast.web.servlet;

import cn.itcast.domain.User;
import cn.itcast.service.UserService;
import cn.itcast.service.impl.UserServiceImpl;

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.util.List;

@WebServlet("/userListServlet")
public class UserListServlet extends HttpServlet {
    
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //1.调用UserService完成查询
        UserService service = new UserServiceImpl();
        List<User> users = service.findAll();
        //2.将list存入request域
        request.setAttribute("users",users);
        //3.转发到list.jsp
        request.getRequestDispatcher("/list.jsp").forward(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        this.doPost(request, response);
    }
}

druid.properties

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///day17
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000