按照上篇文章的分析来具体实现：
定义所需包名来分工：
功能一：显示所有图书：
1、数据层：用双列集合来保存数据，用静态方法来添加数据里嵌套Book类（在实体类包domain里来创建，代码在下面）的构造方法，
public class DB {
private static Map<String,Book> map=new LinkedHashMap<String,Book>();
static
{
map.put("1", new Book("1","java","A",20));
map.put("2", new Book("2","c++","B",21));
map.put("3", new Book("3","PHP","C",22));
map.put("4", new Book("4",".NET","D",23));
map.put("4", new Book("5","Python","E",23));
map.put("6", new Book("6","C#","F",23));
}
/*按照实施过程来创建查找方法，通过类名来调用该静态方法。返回map对象。即上篇文章的
实施过程，可返回参考*/
//注意map的key和value对应public static Map<String,Book> findAllBook(){return map;}public static Book findBookById(String id){return DB.findBookById(id);}}
2、实体层
public class Book {
private String id;
private String name;
private String author;
private double price;
private int num=1;
public Book() {
}
//即对应DB类里的new Book("1","java","A",20)public Book(String id, String name, String author, int price) {super();this.id = id;this.name = name;this.author = author;this.price = price;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}public double getPrice() {return price;}public void setPrice(int price) {this.price = price;}}
3、访问层
//访问层/持久层
public class BookDao {
//查询所有的图书
private DB db=new DB();
public Map<String,Book> findAllBook()
{
return DB.findAllBook();
}
public static Book findBookById(String id){
return DB.findBookById(id);
}
}
4、业务层
public class BookService {
private BookDao bookDao = new BookDao();
// 查询所有图书
public Map<String, Book> findAllBook() {
return bookDao.findAllBook();
}
// 购买图书
public void buyBook(String id, Car car) {
// 取得图书列表
Map<String, Item> map = car.getMap();
// 根据id获得图书
Item item = map.get(id);
if (item == null) {
Book book = bookDao.findBookById(id);
// 加入购物车
item = new Item();
// Book book =new Book();
item.setBook(book);
item.setNum(1);
map.put(id, item);
} else {
item.setNum(item.getNum() + 1);
}
}
public void deleteBook(String id, Car car) {
Map<String, Item> map = car.getMap();
map.remove(id);
}
public void clearCar(Car car) {
Map<String, Item> map = car.getMap();
map.clear();
}
public void updateBook(String id, int num, Car car) {
Map<String, Item> map = car.getMap();
Item item = map.get(id);
item.setNum(num);
}
}
5、控制层
public class ListBookServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
BookService bookservice=new BookService();
Map<String,Book> map=bookservice.findAllBook();
request.setAttribute("map", map);
//请求转发：
request.getRequestDispatcher("/view/listAllBook.jsp").forward(request, response);
}
}6、显示层
listAllBook.jsp
<html>
<body>
<table border="1" align="center" width="80%">
<caption>图书列表</caption>
<tr>
<th>编号</th>
<th>书名</th>
<th>作者</th>
<th>单价</th>
</tr>
<c:forEach var="entry" items="${map}">
<tr>
<td>${entry.value.id}</td>
<td>${entry.value.name}</td>
<td>${entry.value.auther}</td>
<td>${entry.value.price}</td>
<td><a style="text-decoration:none"
href="BuyServlet?id=${entry.value.id}">购买</a></td>
</tr>
</c:forEach>
</table>
</body>
</html>