我是一名java开发人员。我正在用java和mysql开发一个股票应用程序。
我有一个很大的问题。我无法弄清楚应该在哪里放置方法来保存数据。我应该为DB operatios创建一个新类，还是应该将它们放在库存类中。
谢谢！
我的课程是：
package inventory;
public class Item
{
private String bc; // ITEM BARCODE
private String description; // ITEM DESCRIPTION
private int nItm; // NUMBER OF ITEMS IN A PACK OR ITEMS
/**
* Constructor for objects of class item
* - Initialise instance variables bc, description to null and nItm to 0
*/
public Item()
{
// initialise instance variables
bc = null;
description = null;
nItm = 0;
}
/**
* Constructor for objects of class item
* - Initialise instance variables to a given parameters.
* @param bc String item codebar.
* @param description String description of the item.
* @param nItm int items or number of items in a pack
*/
public Item(String bc,String description,int nItm)
{
this.bc = bc;
this.description = description;
this.nItm = nItm;
}
/**
* Gets a codebar from the item
*
* @return A String with the codebar item.
*/
public String getBarcode()
{
// put your code here
return bc;
}
/**
* Gets description from the item
*
* @return A String with the description item.
*/
public String getDescription()
{
return description;
}
/**
* Gets the number of items in stock
*
* @return Number of items in stock.
*/
public int getNumberOfItems()
{
return nItm;
}
/**
* Set the value for codebar
*
* @param bc Barcode item.
*/
public void setBarcode(String bc)
{
this.bc = bc;
}
/**
* Set the value for description
*
* @param description Description item.
*/
public void setDescription(String description)
{
this.description = description;
}
/**
* Set the value for nItm
*
* @param nItm Number of items or items in a pack
*/
public void setNumberOfItems(int nItm)
{
this.nItm = nItm;
}
/**
* Shows an item with this template "| %-16s | %-44s | %5d |"
*/
public void showItem()
{
System.out.print("\f");
System.out.printf("+------------------+----------------------------------------------+-------+\n");
System.out.printf("| BARCODE | DESCRIPTION | STOCK |\n");
System.out.printf("+------------------+----------------------------------------------+-------+\n");
System.out.printf("| %-16s | %-44s | %5d |",this.bc,this.description,this.nItm);
System.out.printf("+-------------------------------------------------------------------------+\n");
}
}
package inventory;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
import DataBases.*;
import java.util.Scanner;
import java.sql.*;
public class Inventory
{
// instance variables - replace the example below with your own
private Item[] inventory; // array of items
public int nreg; // NUMBER OF ITEMS STORED
/**
* Constructor for objects of class Inventory
*/
public Inventory() throws SQLException,ClassNotFoundException,InstantiationException,IllegalAccessException
{
// initialise instance variables
this.inventory = new Item[100];
loadData();
}
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
public void addItem(String bc,String description,int nItm)
{
// put your code here
Item item;
item = new Item(bc,description,nItm);
inventory[nreg] = item;
nreg++;
}
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
public void loadData() throws SQLException,ClassNotFoundException,InstantiationException,IllegalAccessException
{
Mysql c = new Mysql();
ResultSet rs;
c.On();
rs = c.ExeGet("SELECT * FROM item");
while(rs.next())
{
inventory[nreg] = new Item(rs.getString("barcode"),rs.getString("description"),rs.getInt("nItems"));
this.nreg++;
}
c.Off();
}
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
public void searchItem()
{
System.out.print("\f");
int op;
System.out.printf("\tSEARCH MENU\n");
System.out.printf("\t===========\n\n");
System.out.printf("\t1.BY BARCODE.\n");
System.out.printf("\t2.BY ITEM.\n");
System.out.printf("\t3.BY NUMBER OF ITEMS.\n");
System.out.printf("\t0.EXIT.\n\n");
System.out.printf("\tOPTION: ");
Scanner reader = new Scanner(System.in);
op = reader.nextInt();
switch(op)
{
case 0: break;
//case 1: searchByBarcode();break;
//case 2: searchByItem();break;
case 3: searchByNumberOfItems();break;
default: break;
}
}
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
/*
private void searchByBarcode()
{
int op;
int flag = 0;
Item reg = new Item();
do{
System.out.print("\f");
System.out.println("OPTION 1. OK");
System.out.printf("BARCODE: ");
String bc;
Scanner reader = new Scanner(System.in);
bc = reader.nextSt();
// AQUI VA UN TRY COMO UNA CASA
for(int i=0;i<nreg;i++)
{
if (inventory[i].getBarcode() == bc)
{
reg = inventory[i];
flag = 1;
break;
}
}
if (flag == 1)
{
reg.showItem();
}
else
{
System.out.printf("I CAN NOT FIND %d",bc);
}
System.out.println("CONTINUE SEARCHING (0/1): ");
op = reader.nextInt();
}while(op != 1);
}
*/
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
private void searchByNumberOfItems()
{
System.out.print("\f");
System.out.println("OPTION 3. OK");
}
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
public void addNewItem(String barcode,String description,int nItm) throws SQLException,ClassNotFoundException,InstantiationException,IllegalAccessException
{
Mysql c = new Mysql();
Item i = new Item(barcode,description,nItm);
String q = "INSERT INTO inventory.item (barcode,description,nItems) VALUES ('" + i.getBarcode() + "','"
+ i.getDescription() + "'," + i.getNumberOfItems() + ");";
c.On();
c.Exe(q);
c.Off();
nreg++;
}
/**
* An example of a method - replace this comment with your own
*
* @param y a sample parameter for a method
* @return the sum of x and y
*/
public void listItems() throws SQLException,ClassNotFoundException,InstantiationException,IllegalAccessException
{
Mysql c = new Mysql();
ResultSet rs;
c.On();
rs = c.ExeGet("SELECT * FROM item");
System.out.print("\f");
System.out.printf("+------------------+----------------------------------------------+-------+\n");
System.out.printf("| BARCODE | DESCRIPTION | STOCK |\n");
System.out.printf("+------------------+----------------------------------------------+-------+\n");
while(rs.next())
{
//System.out.println("" + rs.getString("barcode") + " " + rs.getString("description") + " " + rs.getInt("nItems"));
System.out.printf("| %-16s | %-44s | %5d |\n",rs.getString("barcode"),rs.getString("description"),rs.getInt("nItems"));
}
System.out.printf("+-------------------------------------------------------------------------+\n");
c.Off();
}
public void listArray()
{
System.out.print("\f");
System.out.printf("+------------------+----------------------------------------------+-------+\n");
System.out.printf("| BARCODE | DESCRIPTION | STOCK |\n");
System.out.printf("+------------------+----------------------------------------------+-------+\n");
for(int i = 0;i<nreg;i++)
{
System.out.printf("| %-16s | %-44s | %5d |\n",inventory[i].getBarcode(),inventory[i].getDescription(),inventory[i].getNumberOfItems());
}
System.out.printf("+-------------------------------------------------------------------------+\n");
System.out.printf("| NUMBER OF ITEMS: %3d |\n",nreg);
System.out.printf("+-------------------------------------------------------------------------+\n");
}
}
package DataBases;
import java.sql.*;
public class Mysql
{
// instance variables - replace the example below with your own
private String host;
private String user;
private String pass;
private String db;
private int port;
private Connection connection;
/**
* Constructor for objects of class Mysql
*/
public Mysql()throws ClassNotFoundException,InstantiationException,IllegalAccessException
{
// initialise instance variables
this.host = "localhost";
this.user = "inventory";
this.pass = "123456";
this.port = 3306;
this.db = "inventory";
this.Init();
}
public Mysql(String host,String user,String pass,int port,String db) throws ClassNotFoundException,InstantiationException,IllegalAccessException
{
this.host = host;
this.user = user;
this.pass = pass;
this.port = port;
this.db = db;
this.Init();
}
public void Init() throws ClassNotFoundException,InstantiationException,IllegalAccessException
{
// put your code here
Class.forName("com.mysql.jdbc.Driver").newInstance();
}
public void On() throws SQLException
{
this.connection = DriverManager.getConnection("jdbc:mysql://"+ this.host +"/" + this.db,this.user,this.pass);
}
public void Off() throws SQLException
{
this.connection.close();
}
public ResultSet ExeGet(String Query) throws SQLException
{
Statement st = this.connection.createStatement();
return (ResultSet) st.executeQuery(Query);
}
public int Exe(String Query) throws SQLException
{
Statement st = this.connection.createStatement();
return st.executeUpdate(Query);
}
}
答案 0 :(得分：0)
快速回答是的，这是一个糟糕的设计对不起，我会采取以下措施来改善它：
尝试实现类之间的松散耦合，每个类应该是一个接口的实现。例如。
public interface ConnectionManager {
void On() throws SQLException;
void Off() throws SQLException;
ResultSet ExeGet(String Query) throws SQLException;
int Exe(String Query) throws SQLException;
}
public class MysqlConnectionManager implements ConnectionManager {
@Override
public void On() throws SQLException {
}
@Override
public void Off() throws SQLException {
}
@Override
public ResultSet ExeGet(String Query) throws SQLException {
}
@Override
public int Exe(String Query) throws SQLException {
}
}
然后你的DAO会有这样的引用（可以注入）：
ConnectionManager connectionManager = new MysqlConnectionManager();
尝试按照骆驼案例练习（Wiki source）
您的属性和关联方法应根据您的属性名称共享相同的名称。
private String barCode;
public String getBarCode(){
return this.barCode;
}
public void setBarCode(final String barCode){
this.barCode = barCode;
}
遵循DAO模式（Wiki source），基本上您需要创建一个类名ItemDao，它将使用DB来处理所有操作＆＃39;项目＆＃39;。
应该将库存重命名为ItemService，并且它不应该只访问数据库DAO，因此如果您需要实现另一个DAO，则很容易替换它。
< / LI>过多地使用System.out.print，而是将您的类配置为使用输出流，因此可以使用文件或字符串输出流轻松配置。
要将数据注入数据库，请使用预准备语句而不是在查询中连接数据（SQL injection）