同一台计算机session共享

亦凉 2022-05-16 06:13 286阅读 0赞

## session ##

由服务器维护跟同一个浏览器的会话，有效时长不超过30分钟（可以在web.xml中设置||在程序中调用invalidate()）  
但要是需要实现不同浏览器共享同一个session则需要考虑session的实现原理——cookie，服务器创建一个session时会将这个session的id在cookie中写给浏览器，所以需要在程序中重写一个同名的cookie  
BuyServlet：

package com.kexin.session1;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    /**
     * 将用户选择要购买的商品加入到服务器维护的session中并重定向到购物车页面
     * Session的原理其实是服务器将SessionID以Cookie的形式写给了浏览器
     * 所以如果想要实现同一台计算机实现同一个session共享的话就需要重写cookie代码
     * 
     * @author KeXin
     *
     */
    @WebServlet("/BuyServlet")
    public class BuyServlet extends HttpServlet {
        
        private static final long serialVersionUID = 1L;
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            // 获取用户选择购买的产品
            Product pro = (Product) new DB().GetProducts().get(request.getParameter("ID"));
    
            // Session的原理其实是服务器将SessionID以Cookie的形式写给了浏览器
            // 所以如果想要实现同一台计算机实现同一个session共享的话就需要重写cookie代码
            HttpSession session = request.getSession();
            Cookie cookie = new Cookie("JSESSIONID", session.getId());
            cookie.setMaxAge(30 * 60);// 最大不超过30min
            cookie.setPath("/SessionGetProduct");// 设置路径
            response.addCookie(cookie);
    
            // 将产品添加到session维护的list中
            List<Product> list = (List<Product>) session.getAttribute("list");
            if (list == null) {
                list = new ArrayList<>();
            }
            list.add(pro);
            session.setAttribute("list", list);
    
            response.sendRedirect("/SessionGetProduct/ListCartServlet");
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }
    
    }

CartListServlet：

package com.kexin.session1;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    @WebServlet("/ListCartServlet")
    public class ListCartServlet extends HttpServlet {
        
        private static final long serialVersionUID = 1L;
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.setCharacterEncoding("UTF-8");
            response.setContentType("text/html;character='utf-8'");
            HttpSession session = request.getSession();
            @SuppressWarnings("unchecked")
            List<Product> list = (List<Product>) session.getAttribute("list");
            PrintWriter writer = response.getWriter();
            writer.write("购买的商品：</br>");
            for(Product p:list){
                writer.write(p.getProductName()+"</br>");
            }
        }
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    
    }

ProductIndex：

package com.kexin.session1;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.io.Serializable;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.Set;
    import java.util.Map.Entry;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /**
     * 商品首页
     * 
     * @author KeXin
     *
     */
    @WebServlet("/ProductIndex")
    public class ProductIndex extends HttpServlet {
        
        private static final long serialVersionUID = 1L;
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            response.setContentType("text/html;character='UTF-8'");
            response.setCharacterEncoding("UTF-8");
            PrintWriter writer = response.getWriter();
            // 展示所有商品
            writer.write("所有商品列表：</br>");
            DB db = new DB();
            Map<String, Product> products = db.GetProducts();
            Set<Entry<String, Product>> product_set = products.entrySet();
            for (Entry<String, Product> e : product_set) {
                Product p = (Product) e.getValue();
                writer.write( p.getProductName() + "<a href = '/SessionGetProduct/BuyServlet?ID=" + p.getID() + "'>购买</a></br>");
            }
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }
    
    }
    
    /**
     * 使用类来模拟数据库
     */
    class DB {
        private Map<String, Product> products = new HashMap();
    
        public DB() {
            this.products.put("1", new Product("1", "马丁靴1", "冬季保暖1"));
            this.products.put("2", new Product("2", "马丁靴2", "冬季保暖2"));
            this.products.put("3", new Product("3", "马丁靴3", "冬季保暖3"));
            this.products.put("4", new Product("4", "马丁靴4", "冬季保暖4"));
            this.products.put("5", new Product("5", "马丁靴5", "冬季保暖5"));
            this.products.put("6", new Product("6", "马丁靴6", "冬季保暖6"));
        }
    
        public Map GetProducts() {
            return products;
        }
    }
    
    /**
     * 使用类Product来模拟数据库记录
     */
    class Product implements Serializable{
        private String ID;
        private String ProductName;
        private String ProductDecs;
    
        public Product(String iD, String productName, String productDecs) {
            super();
            ID = iD;
            ProductName = productName;
            ProductDecs = productDecs;
        }
    
        public String getID() {
            return ID;
        }
    
        public void setID(String iD) {
            ID = iD;
        }
    
        public String getProductName() {
            return ProductName;
        }
    
        public void setProductName(String productName) {
            ProductName = productName;
        }
    
        public String getProductDecs() {
            return ProductDecs;
        }
    
        public void setProductDecs(String productDecs) {
            ProductDecs = productDecs;
        }
    
    }