session: 简单购物车

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session:简单购物车

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// 注： session中的对象(如：Book) 一般都要实现Serializable接口
public class Book implements Serializable{
private String id;
private String name;
private String author;
private float price;
private String description;
public Book(){}
public Book(String id, String name, String author, float price,
String description) {
super();
this.id = id;
this.name = name;
this.author = author;
this.price = price;
this.description = description;
}
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 float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Override
public String toString() {
return "Book [author=" + author + ", description=" + description
+ ", id=" + id + ", name=" + name + ", price=" + price + "]";
}
}
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public class BookDB {
// key: 书的id value: id对应的书对象
private static Map<String, Book> books = new LinkedHashMap<String, Book>();
static{
books.put("1", new Book("1", "葵花宝典", "葛付以", 5.00f, "欲练此功));
books.put("2", new Book("2", "玉女心经", "朱巧玲", 8.00f, "欲练此功));
books.put("3", new Book("3", "辟邪剑法", "邹海洋", 5.00f, "欲练此功));
books.put("4", new Book("4", "金瓶梅", "刘建平", 15.00f, "古代爱"));
books.put("5", new Book("5", "红楼梦", "曹雪芹", 105.00f, "古代"));
}
public static Book findBookById(String bookId){
return books.get(bookId); // map集合的方法
}
public static Map<String,Book> findAllBooks(){
return books;
}
}
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// 显示所有商品
// 提供购买链接
// 提供查看购物车的链接
public class ShowAllBooksServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();

// 显示所有的商品并提供购买链接
out.write("<h1>本站有以下商品</h1>");
Map<String,Book> books = BookDB.findAllBooks();
for(Map.Entry<String, Book> me : books.entrySet()){
out.write(me.getValue().getName() + "  
<a href='/day08/servlet/BuyServlet?id="+ me.getKey() +"'>
购买</a><br/>");
}

// 提供查看购物车的链接
out.write("<a href='/day08/servlet/ShowCartServlet'>查看购物车</a>");
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
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// 完成购物，提供继续购物的超级链接
public class BuyServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();

String id = request.getParameter("id");
Book book = BookDB.findBookById(id);

// 搞一个购物车：先查看有无购物车，若没有，则创建一个，若有，则直接使用
HttpSession session = request.getSession();
List<Book> cart = (List<Book>) session.getAttribute("cart");
if(cart == null){
cart = new ArrayList<Book>();
session.setAttribute("cart", cart);
}
cart.add(book);
out.write(book.getName() + "已经放入您的购物车<br/>");

out.write("<a href='/day08/servlet/ShowAllBooksServlet'>继续购物</a>");

// 若想关闭浏览器之后再次访问时，购物车的信息还在，
// 则须自己写cookie,根据JSESSIONID覆盖session中的cookie
Cookie c = new Cookie("JSESSIONID",session.getId());
c.setPath(request.getContextPath());
c.setMaxAge(Integer.MAX_VALUE);
response.addCookie(c);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
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public class ShowCartServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();

HttpSession session = request.getSession(false); // 只查询
if(session == null){
// 没购物车
out.write("对不起，您还未曾购物！");
}else{
List<Book> cart = (List<Book>) session.getAttribute("cart");
if(cart == null){
// 有购物车，但没购物
out.write("对不起，您还未曾购物！");
}else{
out.write("您购买的商品如下：<br/> ");
for(Book b : cart){
out.write(b.getName() + "<br/>");
}
}
}
out.write("<a href='/day08/servlet/ShowAllBooksServlet'>继续购物</a>");
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
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