JAVA 3层架构及其实例文件/代码规范

桂亭亭
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一图胜万言

架构图

为什么要使用3层架构

1 方便团队分工 利于维护

2 规范代码，在开发软件时对每个层的代码进行规范，固定开发语言的风格。

3 降低更新难度，当软件系统要换数据库时，只要将数据访问层的代码修改就好了。

4 实现"高内聚、低耦合"。易于分配资源。

5 是使得代码逻辑清晰。

各个部分应有的文件

表现层

应该有的文件（jsp+servlet） 

 

业务逻辑层

应该有的文件（service的接口，及其实现的逻辑代码）

数据访问层

应该有的

DAO(全称Data Access Object，意为数据访问接口/对象)

DAO中也应该定义接口，及其实现（具体指增删改查的代码）

entity(意为实体类是数据库表的映射)

utils是工具集的意思，其中连接数据库，关闭数据库/数据源/对象的一些操作应该写在这里的某个类里面

 

各层示例代码

表现层

jsp


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

    <input type="button" id="add" value="新增"><br>
    <hr>
    <table border="1" cellspacing="0" width="800">
        <tr>
            <th>序号</th>
            <th>品牌名称</th>
            <th>企业名称</th>
            <th>排序</th>
            <th>品牌介绍</th>
            <th>状态</th>
            <th>操作</th>

    <c:forEach items="${brands}" var="brand">
        <tr align="center">
            <td>${brand.id}</td>
            <td>${brand.brandName}</td>
            <td>${brand.companyName}</td>
            <td>${brand.ordered}</td>
            <td>${brand.description} </td>
            <td>${brand.status}</td>
            <td><a href="#">修改</a> <a href="#">删除</a></td>
        </tr>
    </c:forEach>

    </table>

    <script>
        document.getElementById("add").onclick = function (){
            location.href = "addBrand.jsp";
        }
    </script>
</body>
</html>

servlet

package com.teaching.jsp.servlet;

import com.teaching.jsp.entity.Brand;
import com.teaching.jsp.service.BrandService;
import com.teaching.jsp.service.impl.BrandServiceImpl;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "AddBrandServlet", value = "/addBrand")
public class AddBrandServlet extends HttpServlet {
    BrandService brandService=new BrandServiceImpl();
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf8");
        //接收参数
        String brandName = request.getParameter("brandName");
        String companyName = request.getParameter("companyName");
        String ordered = request.getParameter("ordered");
        String description = request.getParameter("description");
        String status = request.getParameter("status");
        //封装Brand
        Brand brand = new Brand();
        brand.setBrandName(brandName);
        brand.setDescription(description);
        brand.setCompanyName(companyName);
        brand.setOrdered(Integer.valueOf(ordered));
        brand.setStatus(Integer.valueOf(status));
        //调用Service去处理业务
        brandService.insertBrand(brand);
        //转发到selectAll
        response.sendRedirect("/teachingJsp/selectBrand");
    }
}

业务逻辑层

service 接口

package com.teaching.jsp.service;

import com.teaching.jsp.entity.Brand;

import java.util.List;

public interface BrandService {
    List<Brand> selectAllBrand();

    boolean insertBrand(Brand brand);

    Brand selectBrandById(String id);

    boolean updateBrand(Brand brand);
}

service逻辑

package com.teaching.jsp.service.impl;

import com.teaching.jsp.dao.BrandDao;
import com.teaching.jsp.dao.impl.BrandDaoImpl;
import com.teaching.jsp.entity.Brand;
import com.teaching.jsp.service.BrandService;

import java.util.List;

public class BrandServiceImpl implements BrandService {
    BrandDao brandDao=new BrandDaoImpl();
    @Override
    public List<Brand> selectAllBrand() {
        //逻辑略。。。
        return brandDao.selectAll();
    }

    @Override
    public boolean insertBrand(Brand brand) {
        //逻辑略。。。

        return brandDao.insert(brand);
    }

    @Override
    public Brand selectBrandById(String id) {

        //逻辑略。。。
        return brandDao.selectBrandById(id);
    }

    @Override
    public boolean updateBrand(Brand brand) {
        //逻辑略。。。

        return brandDao.updateBrand(brand);
    }
}

数据访问层

dao 接口

package com.teaching.jsp.dao;

import com.teaching.jsp.entity.Brand;

import java.util.List;
//DAO 的全称是Data Access Object
public interface BrandDao {
    List<Brand> selectAll();

    boolean insert(Brand brand);

    Brand selectBrandById(String id);

    boolean updateBrand(Brand brand);
}

dao 操作

package com.teaching.jsp.dao.impl;

import com.teaching.jsp.dao.BrandDao;
import com.teaching.jsp.entity.Brand;
import com.teaching.jsp.utils.DbUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;


//impl implement是实现的意思
public class BrandDaoImpl implements BrandDao {

    @Override
    public List<Brand> selectAll() {
        List<Brand> list=new ArrayList<>();
        //获取链接
        Connection connection=null;
        try {
            //获取链接
            connection = DbUtils.getConnection();
            //开启事务
            connection.setAutoCommit(false);
            String sql="select * from task1.tb_brand";
            //执行对象
            PreparedStatement ps = connection.prepareStatement(sql);
            //结果集
            ResultSet rs = ps.executeQuery();
            while (rs.next()){
                Brand brand = new Brand(
                        rs.getInt(1),
                        rs.getString(2),
                        rs.getString(3),
                        rs.getInt(4),
                        rs.getString(5),
                        rs.getInt(6)
                        );
                list.add(brand);
            }
            connection.commit();
            DbUtils.close(ps,rs,null);
        } catch (SQLException e) {
            try {
                connection.rollback();
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
            throw new RuntimeException(e);
        } finally {
            try {
                DbUtils.close(connection);
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

        return list;
    }

    @Override
    public boolean insert(Brand brand) {
        //获取链接
        Connection connection=null;
        int row=0;
        try {
            //获取链接
            connection = DbUtils.getConnection();
            //开启事务
            connection.setAutoCommit(false);
            String sql="insert into task1.tb_brand(brand_name,company_name,ordered,description,status) values (?,?,?,?,?)";
            //执行对象
            PreparedStatement ps = connection.prepareStatement(sql);
            ps.setString(1,brand.getBrandName());
            ps.setString(2,brand.getCompanyName());
            ps.setInt(3,brand.getOrdered());
            ps.setString(4,brand.getDescription());
            ps.setInt(5,brand.getStatus());

            row+= ps.executeUpdate();
            connection.commit();
            DbUtils.close(ps,null,null);
        } catch (SQLException e) {
            try {
                connection.rollback();
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
            throw new RuntimeException(e);
        } finally {
            try {
                DbUtils.close(connection);
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

        return row>0;
    }

    @Override
    public Brand selectBrandById(String id) {
        //获取链接
        Connection connection=null;
        Brand brand=null;
        try {
            //获取链接
            connection = DbUtils.getConnection();
            //开启事务
            connection.setAutoCommit(false);
            String sql="select * from tb_brand where id=?";
            //执行对象
            PreparedStatement ps = connection.prepareStatement(sql);
            ps.setInt(1,Integer.valueOf(id));
            //结果集
            ResultSet rs = ps.executeQuery();
            if (rs.next()){
                brand = new Brand(
                        rs.getInt(1),
                        rs.getString(2),
                        rs.getString(3),
                        rs.getInt(4),
                        rs.getString(5),
                        rs.getInt(6)
                );
            }

            connection.commit();
            DbUtils.close(ps,rs,null);
        } catch (SQLException e) {
            try {
                connection.rollback();
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
            throw new RuntimeException(e);
        } finally {
            try {
                DbUtils.close(connection);
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }
        return brand;
    }

    @Override
    public boolean updateBrand(Brand brand) {
        //获取链接
        Connection connection=null;
        int row=0;
        try {
            //获取链接
            connection = DbUtils.getConnection();
            //开启事务
            connection.setAutoCommit(false);
            String sql="update tb_brand set brand_name=?,company_name=?,ordered=?,description=?,status=? where id=?";
            //执行对象
            PreparedStatement ps = connection.prepareStatement(sql);
            ps.setString(1,brand.getBrandName());
            ps.setString(2,brand.getCompanyName());
            ps.setInt(3,brand.getOrdered());
            ps.setString(4,brand.getDescription());
            ps.setInt(5,brand.getStatus());
            ps.setInt(6,brand.getId());

            row+= ps.executeUpdate();
            connection.commit();
            DbUtils.close(ps,null,null);
        } catch (SQLException e) {
            try {
                connection.rollback();
            } catch (SQLException ex) {
                throw new RuntimeException(ex);
            }
            throw new RuntimeException(e);
        } finally {
            try {
                DbUtils.close(connection);
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

        return row>0;
    }
}

entity

package com.teaching.jsp.entity;

public class Brand {
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    private Integer status;


    public Brand() {
    }

    public Brand(Integer id, String brandName, String companyName, String description) {
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.description = description;
    }

    public Brand(Integer id, String brandName, String companyName, Integer ordered, String description, Integer status) {
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.ordered = ordered;
        this.description = description;
        this.status = status;
    }

    public Integer getId() {
        return id;
    }

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

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public Integer getOrdered() {
        return ordered;
    }

    public void setOrdered(Integer ordered) {
        this.ordered = ordered;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "Brand{" +
                "id=" + id +
                ", brandName='" + brandName + ''' +
                ", companyName='" + companyName + ''' +
                ", ordered=" + ordered +
                ", description='" + description + ''' +
                ", status=" + status +
                '}';
    }
}

dbutils

package com.teaching.jsp.utils;


import com.alibaba.druid.pool.DruidDataSourceFactory;
import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

import javax.sql.DataSource;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

public class DbUtils {
    private static DataSource dataSource;

    static {
        Properties prop=new Properties();
        try {
            prop.load(new FileInputStream("F:\JAVA EE Preject\课堂练习\src\com\teaching\jsp\db.properties"));
            System.out.println("iiii");
            dataSource = DruidDataSourceFactory.createDataSource(prop);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public static void test(){
        System.out.println(DbUtils.class.getClassLoader().getResource("db.properties"));
    }

    public static Connection getConnection() throws SQLException {
        System.out.println("iiii111");
        return dataSource.getConnection();
    }

    public static void close(Connection connection) throws SQLException {
        if (connection!=null){
            connection.close();
        }
    }

    public static void close(PreparedStatement ps, ResultSet rs,Connection connection) throws SQLException {
        if (rs!=null){
            rs.close();
        }
        if (ps!=null){
            ps.close();
        }
        if (connection!=null){
            connection.close();
        }
    }
}
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