This article shares with you the relevant methods of using cookies to display recently viewed books for your reference. The specific content is as follows
1.ben package
import java.io.Serializable; public class Book implements Serializable { private String id; private String name; private String price; private String auth; private String publish; private String description; public Book() { } public Book(String id, String name, String price, String auth, String publish, String description) { super(); this.id = id; this.name = name; this.price = price; this.auth = auth; this.publish = publish; this.description = description; } public String getDescription() { return description; } public void setDescription(String description) { 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 getPrice() { return price; } public void setPrice(String price) { this.price = price; } public String getAuth() { return auth; } public void setAuth(String auth) { this.auth = auth; } public String getPublish() { return publish; } public void setPublish(String publish) { this.publish = publish; } } 2. Dao package
import java.util.LinkedHashMap;import java.util.Map; import cn.huiyu.ben.Book; public class BookDao { private static Map<String,Book> bookMap = new LinkedHashMap<String, Book>(); private BookDao() { } static{ bookMap.put("1", new Book("1","1111","11.0","zqwang","111 Press","111111111")); bookMap.put("2", new Book("2","2222","22.0","zqwang","2222222222")); bookMap.put("3", new Book("3","3333","33.0","zqwang","3333333333")); } public static Map<String,Book> getBooks(){ return bookMap; } public static Book getBook(String id){ return bookMap.get(id); }} 3.servlet
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); //1. Query all books in the database to display Map<String,Book> map = BookDao.getBooks(); for(Map.Entry<String, Book> entry : map.entrySet()){ Book book = entry.getValue(); response.getWriter().write("<a href='"+request.getContextPath()+"/servlet/BookInfoServlet?id="+book.getId()+"'>"+book.getName()+"</a><br>"); } response.getWriter().write("<hr>"); //2. Show the books I have read before Cookie [] cs = request.getCookies(); Cookie findC = null; if(cs!=null){ for(Cookie c : cs){ if("last".equals(c.getName())){ findC = c; } } } if(findC == null){ response.getWriter().write("I haven't read any books!"); }else{ response.getWriter().write("The books you have browsed:<br>"); String[] ids = findC.getValue().split(","); for(String id : ids){ Book book = BookDao.getBook(id); response.getWriter().write(book.getName()+"<br>"); } } } 4.servlet
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); //1. Get the id of the book to be read, query the database to find the book, and output the detailed information of the book String id = request.getParameter("id"); Book book = BookDao.getBook(id); if(book==null){ response.getWriter().write("This book cannot be found!"); return; }else{ response.getWriter().write("<h1>Title:"+book.getName()+"</h1>"); response.getWriter().write("<h3>Author:"+book.getAuth()+"</h3>"); response.getWriter().write("<h3>Selling price:"+book.getPrice()+"</h3>"); response.getWriter().write("<h3>Publisher:"+book.getPublish()+"</h3>"); response.getWriter().write("<h3>Description:"+book.getDescription()+"</h3>"); } //2. Send cookies to save the last book you read // --- 1 --> 1 // 1 --2,1 --> 2,1 // 2,1--3,2,1 --> 3,2,1 // 3,2,1 --> 3,2,1 --> 4,3,2 --> 4,3,2 // 4,3,2 --3,4,2 --> 3,4,2 String ids = ""; Cookie [] cs = request.getCookies(); Cookie findC = null; if(cs!=null){ for(Cookie c : cs){ if("last".equals(c.getName())){ findC = c; } } } if(findC == null){ //Explanation records that have not read the book before ids += book.getId(); }else{ //Explanation records of books that have been read in history before, and a new record needs to be calculated based on the history String [] olds = findC.getValue().split(","); StringBuffer buffer = new StringBuffer(); buffer.append(book.getId()+","); for(int i = 0;i<olds.length && buffer.toString().split(",").length<3 ;i++){ String old = olds[i]; if(!old.equals(book.getId())){ buffer.append(old+","); } } ids = buffer.substring(0, buffer.length()-1); } Cookie lastC = new Cookie("last",ids); lastC.setMaxAge(3600*24*30); lastC.setPath(request.getContextPath()); response.addCookie(lastC); }The above is all about this article. I hope it will be helpful for everyone to learn how to use cookies to display recently viewed books.