Cookie技术案例-——显示曾经浏览过的商品

CookieDemo1

import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedHashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CookieDemo1 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();
		// 输出所有商品
		out.write("本站有如下商品:<br/>");
		Map<String, Book> map = Db.getAll();
		for (Map.Entry<String, Book> entry : map.entrySet())
		{
			Book book = entry.getValue();
			out.print("<a target=\"_blank\" href='/day07/servlet/cookieDemo2?id="
							+ book.getId()
							+ "'>"
							+ book.getName()
							+ "</a><br/>");

		}
		// 显示用户看过的商品
		out.print("<br/>你曾经看过的商品<br/>");
		Cookie cookies[] = request.getCookies();
		for (int i = 0; cookies != null && i < cookies.length; i++)
		{
			if (cookies[i].getName().equals("bookHistory"))
			{
				String ids[] = cookies[i].getValue().split("\\,");// 2,3,1
				for (String id : ids)
				{
					Book book = (Book) Db.getAll().get(id);
					out.print("<a target=\"_blank\" href='/day07/servlet/cookieDemo4?id="
									+ book.getId()
									+ "'>"
									+ book.getName()
									+ "</a><br/>");
				}
			}
		}
	}
}
//用Db模拟数据库
class Db
{
	private static Map<String, Book> map = new LinkedHashMap<String, Book>();
	static
	{
		map.put("1", new Book("1", "JavaWeb开发", "老k", "一本好书"));
		map.put("2", new Book("2", "jdbc开发", "老张", "一本好书"));
		map.put("3", new Book("3", "spring开发", "老li", "一本好书"));
		map.put("4", new Book("4", "struts开发", "老张", "一本好书"));
		map.put("5", new Book("5", "android开发", "老bi", "一本好书"));
	}

	public static Map getAll()
	{
		return map;
	}

}

class Book
{
	private String id;
	private String name;
	private String author;
	private String description;

	public Book()
	{
		super();
	}

	public Book(String id, String name, String author, String description)
	{
		this.id = id;
		this.name = name;
		this.author = author;
		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 String getDescription()
	{
		return description;
	}

	public void setDescription(String description)
	{
		this.description = description;
	}
}

CookieDemo2

 

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//显示详细信息的servlet
public class CookieDemo2 extends HttpServlet
{

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException
	{
		// 根据用户带过来的id，显示相应的详细信息
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		String id = request.getParameter("id");
		Book book = (Book) Db.getAll().get(id);
		out.write(book.getId() + "<br/>");
		out.write(book.getName() + "<br/>");
		out.write(book.getAuthor() + "<br/>");
		out.write(book.getDescription() + "<br/>");
		// 2.构建cookie，回写给浏览器；
		String cookieValue = buildCookie(id, request);
		Cookie cookie = new Cookie("bookHistory", cookieValue);
		cookie.setMaxAge(1 * 30 * 24 * 3600);// 1 个月
		cookie.setPath("/day07");
		response.addCookie(cookie);
	}

	private String buildCookie(String id, HttpServletRequest request)
	{
		// bookHistory =null 1 1
		// bookHistory=2,5,1 1 1,2,5
		// bookHistory=2,5,4 1 1,2,5
		// bookHistroy=2,5 1 1,2,5 // 假如列表最多3个
		String bookHistroy = null;
		Cookie cookies[] = request.getCookies();
		for (int i = 0; cookies != null && i < cookies.length; i++)
		{
			if (cookies[i].getName().equals("bookHistory"))
			{
				bookHistroy = cookies[i].getValue();
			}
		}
		if (bookHistroy == null)
			return id;
		// if(bookHistroy.contains(id))不能这样 21,23 也包括1
		List<String> list = Arrays.asList(bookHistroy.split("\\,"));
		LinkedList<String> linkedlist = new LinkedList<String>(list);
		if (list.contains(id))
		{
			linkedlist.remove(id);
			linkedlist.addFirst(id);
		} else
		{
			if (list.size() >= 3)
			{
				linkedlist.removeLast();
				linkedlist.addFirst(id);
			} else
				linkedlist.addFirst(id);
		}
		StringBuffer sb = new StringBuffer();
		for (String bid : linkedlist)
		{
			sb.append(bid + ",");
		}
		return sb.deleteCharAt(sb.length() - 1).toString();
	}

}