$3 : 水项目实战 - 水果库存系统

javase知识点复习：

final关键字：http://t.csdn.cn/bvFgu

接口的定义，特性，实现，继承：http://t.csdn.cn/tbXl3

异常：http://t.csdn.cn/VlS0Z

DAO的概念和角色（设计理念）： DAO-称之为数据访问对象，其中的方法都是单精度方法。
单精度指的是这个方法的粒度不能再分了，已经非常细了（因此也称之为细粒度）

fruit --- controller --- Menu.class

fruit --- dao --- FruitDAO.interface

/ impl --- FruitDAOImpl.class

/base --- BaseDAO.class

fruit --- pojo --- Fruit.class

fruit --- view --- Client.class

Menu.class

package com.atguigu.fruit.controller;

import com.atguigu.fruit.dao.FruitDAO;
import com.atguigu.fruit.dao.impl.FruitDAOImpl;
import com.atguigu.fruit.pojo.Fruit;

import java.util.List;
import java.util.Scanner;

//菜单类
public class Menu {

    Scanner input = new Scanner(System.in);
    FruitDAO fruitDAO = new FruitDAOImpl();

    //显示主菜单
    public int showMainMenu(){
        System.out.println("=================欢迎使用水果库存系统=====================");
        System.out.println("1.查看水果库存列表");
        System.out.println("2.添加水果库存信息");
        System.out.println("3.查看特定水果库存信息");
        System.out.println("4.水果下架");
        System.out.println("5.退出");
        System.out.println("======================================================");
        System.out.print("请选择：");

        int slt = input.nextInt();
        return slt ;
    }

    //查看水果库存列表
    public void showFruitList(){
        List<Fruit> fruitList = fruitDAO.getFruitList();
        System.out.println("------------------------------------------------------");
        System.out.println("编号\t\t名称\t\t单价\t\t库存\t\t备注");
        if(fruitList==null || fruitList.size()<=0){
            System.out.println("对不起，库存为空！");
        }else{
            for (int i = 0; i < fruitList.size(); i++) {
                Fruit fruit = fruitList.get(i);
                System.out.println(fruit);
            }
        }
        System.out.println("------------------------------------------------------");
    }

    //添加水果库存信息 -- 业务方法：添加库存记录
    public void addFruit(){
        System.out.print("请输入水果名称：");
        String fname = input.next() ;
        Fruit fruit = fruitDAO.getFruitByFname(fname);
        if(fruit==null){    //说明库存中没有这个名称的水果 - 添加
            System.out.print("请输入水果单价：");
            int price = input.nextInt() ;
            System.out.print("请输入水果库存量：");
            int fcount = input.nextInt() ;
            System.out.print("请输入水果备注：");
            String remark = input.next() ;

            //封装成一个新的fruit对象
            fruit = new Fruit(0,fname , price , fcount , remark ) ;
            //调用DAO的添加方法
            fruitDAO.addFruit(fruit);
        }else{ // 说明库存中有这个名称的水果 - 修改
            System.out.print("请输入追加的库存量：");
            int fcount = input.nextInt() ;
            fruit.setFcount(fruit.getFcount()+fcount);
            //调用DAO的修改方法
            fruitDAO.updateFruit(fruit);
        }
        System.out.println("添加成功！");
    }

    //查看指定水果库存信息
    public void showFruitInfo(){
        System.out.print("请输入水果名称：");
        String fname = input.next() ;
        Fruit fruit = fruitDAO.getFruitByFname(fname);
        if(fruit==null){
            System.out.println("对不起，没有找到指定的水果库存记录！");
        }else{
            System.out.println("------------------------------------------------------");
            System.out.println("编号\t\t名称\t\t单价\t\t库存\t\t备注");
            System.out.println(fruit);
            System.out.println("------------------------------------------------------");
        }
    }

    //水果下架
    public void delFruit(){
        System.out.print("请输入水果名称：");
        String fname = input.next() ;
        Fruit fruit = fruitDAO.getFruitByFname(fname);
        if(fruit==null){
            System.out.println("对不起，没有找到需要下架的水果信息！");
        }else{
            System.out.print("是否确认下架？(Y/N)");
            String slt = input.next() ;
            if("y".equalsIgnoreCase(slt)){
                fruitDAO.delFruit(fname);
                System.out.println("下架成功！");
            }
        }
    }

    //退出
    public boolean exit(){
        System.out.print("是否确认退出？(Y/N)");
        String slt = input.next();
        return !"Y".equalsIgnoreCase(slt);//equalsIgnoreCase('Y') ---> true  !取反
    }

}

BaseDAO.class

package com.atguigu.fruit.dao.base;

import com.atguigu.fruit.pojo.Fruit;

import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

//抽象方法不能直接new 必须只能继承 允许有构造方法
public abstract class BaseDAO<T> {
    //向上提取通用常量，多个DAO可用
    public final String DRIVER = "com.mysql.jdbc.Driver";
    public final String URL = "jdbc:mysql://localhost:3306/fruitdb?useUnicode=true&characterEncoding=utf-8&useSSL=false";
    public final String USER = "root";
    public final String PWD = "123456";

    protected Connection conn;//连接对象
    protected PreparedStatement psmt;//预处理命令对象
    protected ResultSet rs;//返回结果集

    //T的class对象
    private Class entityClass;

    public BaseDAO(){
        //getClass() 获取Class对象，当前我们执行的是new FruitDAOImpl() , 创建的是FruitDAOImpl的实例
        //那么子类构造方法内部首先会调用父类（BaseDAO）的无参构造方法
        //因此此处的getClass()会被执行，但是getClass获取的是FruitDAOImpl的Class
        //所以getGenericSuperclass()获取到的是BaseDAO的Class
        Type genericType = getClass().getGenericSuperclass();
        //ParameterizedType 参数化类型
        Type[] actualTypeArguments = ((ParameterizedType) genericType).getActualTypeArguments();
        //获取到的<T>中的T的真实的类型
        Type actualType = actualTypeArguments[0];
        try {
            entityClass = Class.forName(actualType.getTypeName());
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    //获取连接
    protected Connection getConn() {
        try {
            //1.加载驱动
            Class.forName(DRIVER);
            //2.通过驱动管理器获取连接对象
            return DriverManager.getConnection(URL, USER, PWD);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    //关闭资源
    protected void close(ResultSet rs, PreparedStatement psmt, Connection conn) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (psmt != null) {
                psmt.close();
            }
            if (conn != null && !conn.isClosed()) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    //给预处理命令对象设置参数
    private  void setParams(PreparedStatement psmt,Object... params) throws SQLException {
        if (params != null && params.length > 0) {
            for (int i = 0; i < params.length; i++) {
                psmt.setObject(i + 1, params[i]);
            }
        }
    }

    //执行更新，返回影响行数
    protected int executeUpdate(String sql , Object... params){
        boolean insertFlag = false ;
        insertFlag = sql.trim().toUpperCase().startsWith("INSERT");
        try {
            conn = getConn();
            if(insertFlag){
                psmt = conn.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);
            }else {
                psmt = conn.prepareStatement(sql);
            }
            setParams(psmt,params);
            int count = psmt.executeUpdate() ;

            rs = psmt.getGeneratedKeys();
            if(rs.next()){
                return ((Long)rs.getLong(1)).intValue();
            }
            return count ;
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            close(rs,psmt,conn);
        }
        return 0;
    }

    //通过反射技术给obj对象的property属性赋propertyValue值
    private void setValue(Object obj ,  String property , Object propertyValue){
        Class clazz = obj.getClass();
        try {
            //获取property这个字符串对应的属性名 ， 比如 "fid"  去找 obj对象中的 fid 属性
            Field field = clazz.getDeclaredField(property);
            if(field!=null){
                field.setAccessible(true);
                field.set(obj,propertyValue);
            }
        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    //执行复杂查询，返回例如统计结果
    protected Object[] executeComplexQuery(String sql , Object... params){
        try {
            conn = getConn() ;
            psmt = conn.prepareStatement(sql);
            setParams(psmt,params);
            rs = psmt.executeQuery();

            //通过rs可以获取结果集的元数据
            //元数据：描述结果集数据的数据 , 简单讲，就是这个结果集有哪些列，什么类型等等

            ResultSetMetaData rsmd = rs.getMetaData();
            //获取结果集的列数
            int columnCount = rsmd.getColumnCount();
            Object[] columnValueArr = new Object[columnCount];
            //6.解析rs
            if(rs.next()){
                for(int i = 0 ; i<columnCount;i++){
                    Object columnValue = rs.getObject(i+1);     //33    苹果      5
                    columnValueArr[i]=columnValue;
                }
                return columnValueArr ;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close(rs,psmt,conn);
        }
        return null ;
    }

    //执行查询，返回单个实体对象
    protected T load(String sql , Object... params){
        try {
            conn = getConn() ;
            psmt = conn.prepareStatement(sql);
            setParams(psmt,params);
            rs = psmt.executeQuery();

            //通过rs可以获取结果集的元数据
            //元数据：描述结果集数据的数据 , 简单讲，就是这个结果集有哪些列，什么类型等等

            ResultSetMetaData rsmd = rs.getMetaData();
            //获取结果集的列数
            int columnCount = rsmd.getColumnCount();
            //6.解析rs
            if(rs.next()){
                T entity = (T)entityClass.newInstance();

                for(int i = 0 ; i<columnCount;i++){
                    String columnName = rsmd.getColumnName(i+1);            //fid   fname   price
                    Object columnValue = rs.getObject(i+1);     //33    苹果      5
                    setValue(entity,columnName,columnValue);
                }
                return entity ;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } finally {
            close(rs,psmt,conn);
        }
        return null ;
    }

    //执行查询，返回List
    protected List<T> executeQuery(String sql , Object... params){
        List<T> list = new ArrayList<>();
        try {
            conn = getConn() ;
            psmt = conn.prepareStatement(sql);
            setParams(psmt,params);
            rs = psmt.executeQuery();

            //通过rs可以获取结果集的元数据
            //元数据：描述结果集数据的数据 , 简单讲，就是这个结果集有哪些列，什么类型等等

            ResultSetMetaData rsmd = rs.getMetaData();
            //获取结果集的列数
            int columnCount = rsmd.getColumnCount();
            //6.解析rs
            while(rs.next()){
                T entity = (T)entityClass.newInstance();

                for(int i = 0 ; i<columnCount;i++){
                    String columnName = rsmd.getColumnName(i+1);            //fid   fname   price
                    Object columnValue = rs.getObject(i+1);     //33    苹果      5
                    setValue(entity,columnName,columnValue);
                }
                list.add(entity);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } finally {
            close(rs,psmt,conn);
        }
        return list ;
    }
}

FruitDAOImpl.class

package com.atguigu.fruit.dao.impl;

import com.atguigu.fruit.dao.FruitDAO;
import com.atguigu.fruit.dao.base.BaseDAO;
import com.atguigu.fruit.pojo.Fruit;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;
//接口实现类
public class FruitDAOImpl extends BaseDAO<Fruit> implements FruitDAO {


    //查询库存列表
    @Override
    public List<Fruit> getFruitList() {
        return super.executeQuery("select * from t_fruit");
    }

    //新增库存
    @Override
    public boolean addFruit(Fruit fruit) {
        String sql = "insert into t_fruit values(0,?,?,?,?)";
        return super.executeUpdate(sql,fruit.getFname(),fruit.getPrice(),fruit.getFcount(),fruit.getRemark())>0;
    }

    //修改库存
    @Override
    public boolean updateFruit(Fruit fruit) {
        String sql = "update t_fruit set fcount = ? where fid = ? " ;
        return super.executeUpdate(sql,fruit.getFcount(),fruit.getFid())>0;
    }

    //根据名称查询特定库存
    @Override
    public Fruit getFruitByFname(String fname) {
        return super.load("select * from t_fruit where fname like ? ",fname);
    }
    //删除特定库存记录
    @Override
    public boolean delFruit(String fname) {
        String sql = "delete from t_fruit where fname like ? " ;
        return super.executeUpdate(sql,fname) > 0;
    }
}

FruitDAO.interface

package com.atguigu.fruit.dao;

import com.atguigu.fruit.pojo.Fruit;

import java.util.List;

public interface FruitDAO {
    //查询库存列表
    List<Fruit> getFruitList();

    //新增库存
    boolean addFruit(Fruit fruit);

    //修改库存
    boolean updateFruit(Fruit fruit);

    //根据名称查询特定库存
    Fruit getFruitByFname(String fname);

    //删除特定库存记录
    boolean delFruit(String fname);
}

Fruit.class

package com.atguigu.fruit.pojo;

public class Fruit {
    private Integer fid ;
    private String fname ;
    private Integer price ;
    private Integer fcount ;
    private String remark ;

    public Fruit(){}

    public Fruit(Integer fid, String fname, Integer price, Integer fcount, String remark) {
        this.fid = fid;
        this.fname = fname;
        this.price = price;
        this.fcount = fcount;
        this.remark = remark;
    }

    public Integer getFid() {
        return fid;
    }

    public void setFid(Integer fid) {
        this.fid = fid;
    }

    public String getFname() {
        return fname;
    }

    public void setFname(String fname) {
        this.fname = fname;
    }

    public Integer getPrice() {
        return price;
    }

    public void setPrice(Integer price) {
        this.price = price;
    }

    public Integer getFcount() {
        return fcount;
    }

    public void setFcount(Integer fcount) {
        this.fcount = fcount;
    }

    public String getRemark() {
        return remark;
    }

    public void setRemark(String remark) {
        this.remark = remark;
    }

    @Override
    public String toString() {
        return fid + "\t\t" + fname + "\t\t" + price +"\t\t" + fcount +"\t\t" + remark ;
    }
}

Client.class

package com.atguigu.fruit.view;

import com.atguigu.fruit.controller.Menu;

public class Client {
    public static void main(String[] args) {
        Menu m = new Menu() ;

        boolean flag = true ;
        while(flag){
            //调用显示主菜单的方法
            int slt = m.showMainMenu();
            switch(slt){
                case 1:
                    //显示库存列表
                    m.showFruitList();
                    break;
                case 2:
                    m.addFruit();
                    break;
                case 3:
                    m.showFruitInfo();
                    break;
                case 4:
                    m.delFruit();
                    break;
                case 5:
                    flag=m.exit();
                    break;
                default:
                    System.out.println("你不按套路出牌！");
                    break;
            }
        }
        System.out.println("谢谢使用！再见！");
    }
}