j假设一个数据库和书对象
//数据库
class Db{
private static Map<String, Book> map = new LinkedHashMap();
static{
map.put("1", new Book("1","web开发","老张"));
map.put("2", new Book("2","spring","老毕"));
map.put("3", new Book("3","struts","老张"));
map.put("4", new Book("4","jdbc","老黎"));
}
//拿到书
public static Map getAll(){
return map;
}
}
//书对象
class Book{
private String id;
private String name;
private String author;
public Book() {
super();
}
public Book(String id, String name, String author) {
super();
this.id = id;
this.name = name;
this.author = author;
}
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;
}
}
将书的列表显示出来
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置防止乱码
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
out.write("本网站有如下商品:<br>");
request.getSession();
Map<String,Book> map = Db.getAll();
for(Map.Entry<String,Book> entry : map.entrySet()){
Book book = entry.getValue();
//重写url防止用户禁用cookie
String url = response.encodeURL("BuyServlet?id="+book.getId());
out.write(book.getName()+"<a href='"+url+"' target='_blank'>购买</a><br>");
}
}
点击购买后
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String id = request.getParameter("id");
//根据id号找到书
Map<String, Book> map = Db.getAll();
Book book = map.get(id);
HttpSession session = request.getSession(false);
//从session得到书,使用list存放
List list = (List) session.getAttribute("list");
if(list==null){
list = new ArrayList();
session.setAttribute("list", list);
}
list.add(book);
//重写url
String url = response.encodeRedirectURL("/day07/ListCartServlet");
response.sendRedirect(url);
}
最后显示购买的界面
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置防止乱码
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
//由session得到书目
HttpSession session = request.getSession(false);
//对session进行判断
if(session==null){
out.write("you do not hava to purchase any goods<br>");
return;
}
out.write("You purchase the following commodity: <br>");
List<Book> list = (List) session.getAttribute("list");
for(Book book : list){
out.write(book.getName()+"<br>");
}
}