Session案例,顯示商品瀏覽記錄
阿新 • • 發佈:2019-01-22
相對於Cookie而言,Session並不經常在伺服器中使用,因為session為每一個瀏覽器使用者建立了一個session,這樣對伺服器的要求無形之中高了很多,而cookie是對每個瀏覽器傳送資料,所以伺服器負擔小,所以大部分瀏覽器還是選擇使用cookie來實現瀏覽記錄的顯示。
當用戶的瀏覽器禁用Cookie的時候,可以使用超連結裡面帶著指定的id去訪問servlet,具體程式碼為response.encodeURL("/");裡面放具體的servlet訪問地址,這樣的話,就能帶著指定的id去訪問從而解決了禁用cookie問題,
如果使用者沒有禁用cookie,則第一次他會將超連結和cookie同時傳送回去,但是,當第二次訪問的時候,伺服器發現他返回了cookie,則就不在重新寫超連結了
本案例是使用session來實現模仿當用戶在首頁點選了商品名字的時候,通過session記錄了各個他點選的商品的名字,然後當選擇結賬的時候,自動將他選擇購買的商品顯示出來,下面上程式碼
第一段程式碼是用來充當首頁的servlet,裡面假設了如果使用者禁用cookie的情況
package com.bird.shopping; import java.io.IOException; import java.io.PrintWriter; import java.io.Serializable; import java.util.LinkedHashMap; import java.util.Map; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @category 模擬網站首頁的servlet用來顯示所有的商品 * @author Bird * */ public class ListBookServlet extends HttpServlet { private static final long serialVersionUID = 1L; 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(); request.getSession();//注意,一定要得到session,否則無法進行自動的id新增 out.write("本網站有如下商品</br>"); Map<String,Book> map = DB.getAll(); for(Map.Entry<String, Book> entry : map.entrySet()){ Book book = entry.getValue(); String url = response.encodeURL("/Web/servlet/BuyServlet?id="+book.getId()+""); out.write(book.getName()+"<a href='"+url+"' target='_blank'>購買</a></br>"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } } class DB{ //必須使用連結串列Map進行有序儲存 private static Map<String,Book> map = new LinkedHashMap<String,Book>(); static{ map.put("1", new Book("1","javaweb開發詳解","老張","一本好書!!!")); map.put("2", new Book("2","jdbc開發詳解","老張","一本好書!!!")); map.put("3", new Book("3","sping開發詳解","老黎","一本好書!!!")); map.put("4", new Book("4","struts開發詳解","老宇","一本好書!!!")); map.put("5", new Book("5","heibrate開發詳解","老畢","一本好書!!!")); } public static Map<String,Book> getAll(){ return map; } } class Book implements Serializable{ private static final long serialVersionUID = 1L; private String id; private String name; private String author; private String description; public Book(){} 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; } }
第二段程式碼,是根據帶過來的id將對應的商品名稱放入到session中,以備下面的結賬,當然,最終的跳轉一定要使用瀏覽器的本地重定向,而不是伺服器的請求重定向,否則會反覆訪問這個servlet幹同樣的事情,導致多次的購買
package com.bird.shopping; import java.io.IOException; import java.util.ArrayList; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * @category 購買 * @author Bird * */ public class BuyServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String id = request.getParameter("id"); Book book = DB.getAll().get(id); HttpSession session = request.getSession(); //從session獲得使用者儲存的資料(購物車) @SuppressWarnings("unchecked") List<Book> list = (List<Book>) session.getAttribute("list"); if(list==null){ list = new ArrayList<Book>(); session.setAttribute("list", list); } list.add(book); String url = response.encodeRedirectURL(request.getContextPath()+"/servlet/ListCarServlet"); //request.getRequestDispatcher("/servlet/ListCarServlet").forward(request, response); response.sendRedirect(url); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }
第三段程式碼,用來顯示已經購買的商品名稱
package com.bird.shopping;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* @category 顯示使用者購買的商品
* @author Bird
*
*/
public class ListCarServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
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();
if(session == null){
out.write("您沒有購買任何商品");
return;
}
out.write("您購買了如下商品:</br>");
@SuppressWarnings("unchecked")
List<Book> list = (List<Book>) session.getAttribute("list");
for(Book book: list){
out.write(book.getName());
out.write("</br>");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}