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 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 {//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ClassType genericType = getClass().getGenericSuperclass();//ParameterizedType 参数化类型Type[] actualTypeArguments = ((ParameterizedType) genericType).getActualTypeArguments();//获取到的中的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rsif(rs.next()){for(int i = 0 ; i executeQuery(String sql , Object... params){List 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rswhile(rs.next()){T entity = (T)entityClass.newInstance();for(int i = 0 ; i

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 implements FruitDAO {//查询库存列表@Overridepublic List getFruitList() {return super.executeQuery("select * from t_fruit");}//新增库存@Overridepublic 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@Overridepublic 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@Overridepublic Fruit getFruitByFname(String fname) {return super.load("select * from t_fruit where fname like ? ",fname);}//删除特定库存记录@Overridepublic boolean delFruit(String fname) {String sql = "delete from t_fruit where fname like ? " ;return super.executeUpdate(sql,fname) > 0;}
}

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 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);
}

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

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！");}
}