servlet 会话管理

一.URL　重写

URL 重写是一种会话跟踪技术,它将一个或多个token添加到URL的查询字符串中,每个token通常为 key=value形式,如下:

url?key-1=value-1&key-2=value-2 ... &key-n=value-n//url和token间用?号分割,token间用与号(&)

URL重写适合tokens无须在太多的URL间传递的情况;它有如下限制:

1.URL在某些浏览器上的最大传递为2000字符

2.静态页面很难传值

3.一个页面有多个URL,很难处理

4.某些字符,如问号,与和空格等必须用base64编码

5.所有信息都是可见的,某些情况不太合适

实例: 显示最受旅客青睐的10个伦敦和巴黎的景点

package app02a;
/*
 * 显示最受旅客青睐的10个伦敦和巴黎的景点
 */
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
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;

@WebServlet(name ="Top10Servlet", urlPatterns= {"/top10","/top"})
public class Top10Servlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
    private List<String> londonAttractions;
    private List<String> parisAttractions;
    
    @Override
    public void init() throws ServletException{
        londonAttractions = new ArrayList<String>(10);
        londonAttractions.add("Buckingham Palace");
        londonAttractions.add("london Eye");
        londonAttractions.add("British Museum");
        londonAttractions.add("National Gallery");
        londonAttractions.add("big ben");
        londonAttractions.add("Tower of london");
        londonAttractions.add("Canary Wharf");
        londonAttractions.add("2012 Olympic Park");
        londonAttractions.add("St Paul's CathedRal");
        londonAttractions.add("newyork");
        
        parisAttractions = new ArrayList<String>(10);
        for(int i = 0; i < 10; i++)
            parisAttractions.add("parisAttractions" + (i+1));
    }
    @Override
    public void doGet(HttpServletRequest request,HttpServletResponse response)
                throws ServletException,IOException{
        String city = request.getParameter("city");
        if(city != null && (city.equals("london") || city.equals("paris"))) {
            // show attractions
            showAttractions(request,response,city);
        }else {
            //show main page
            showMainPage(request,response);
        }
    }
    
    private void showMainPage(HttpServletRequest requset,HttpServletResponse response) 
                throws ServletException,IOException{
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter();
        writer.print("<!DOCTYPE html>"
                + "<html><head><meta language='en' enconding='utf-8'><title>Top 10 attractions</title></head>"
                + "<body>Please select a city: <br />"
                // 此处为相对url,  borwer 会在当前url后面加上href的内容 http://localhost:8080/app02a/top10?city=london
                + "<a href='?city=london'>London</a> <br />" 
                + "<a href='?city=paris'>Paris</a></body></html>");
    }
    private void showAttractions(HttpServletRequest request, HttpServletResponse response, String city) 
                throws ServletException, IOException {
        int page = 1;
        // 得到page的值
        String pageParameter = request.getParameter("page");
        if(pageParameter != null) {
            try {
                page = Integer.parseInt(pageParameter);
            }catch(NumberFormatException e) {
                //do nothing and retain default value for page
            }
            if(page > 2) {
                page = 1;
            }
        }
            List<String> attractions = null;
            if(city.equals("london"))
                attractions = londonAttractions;
            else if(city.equals("paris"))
                attractions = parisAttractions;
            response.setContentType("text/html");
            PrintWriter writer = response.getWriter();
            writer.print("<html><head>"
                    + "<title> Top 10 Attractions </title>"  
                    + "</head><body>");
            writer.print("<a href='top10'>Seletct City</a>");
            writer.print("<hr/>page " + page + "<hr />");
            int start = page*5-5;
            for( int i = start; i < start + 5; i++) {
                writer.print(attractions.get(i) + "<br />");
            }
            writer.print("<hr style='color:blue;' />"
                    + "<a href='?city="+ city
                    + "&page=1'>page 1</a>");
            writer.print("&nbsp; <a href='?city=" + city +
                    "&page=2'>page 2</a>");
        }
    }

二.隐藏域

使用隐藏域来保持状态类似于URL重写技术, 但不是将值附加到URL上,而是放到HTML的表单的隐藏域中.当表单提交时,隐藏域的值也它是条件到服务器端,隐藏域技术仅当网页有表单时有效,相对于URL的优势在于,没有字符限制,同时无须额外编码.但是不适合跨越多个页面

例: 通过隐藏域来更新客户信息

package app02a.hiddenfields;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;
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 java.sql.*;
//URL分别映射三个URL 前两个会调用doGet,  而 update会调用dopost方法
@WebServlet(name = "CustomerServlet", urlPatterns= {
        "/customer", "/editCustomer", "/updateCustomer"
})
public class CustomerServlet extends HttpServlet{
    private static final long serialVersionUID = -20L;
    //存储customers 数据
    private Vector<Customer> customers = new Vector<Customer>();
    @Override
    public void init() throws ServletException{
        Customer customer1 = new Customer();
        ResultSet rs = null;
        // 读取数据库的customer数据
        try (Statement stmt = new Mysql_JDBC().getStatement()){
             rs = stmt.executeQuery("SELECT cust_id,cust_name,cust_city FROM mysql_test.customer where cust_id <100 ");
             while(rs.next())
             {
                 Customer cust = new Customer();
                 cust.setId(rs.getInt("cust_id"));
                 cust.setName(rs.getString("cust_name"));
                 cust.setCity(rs.getString("cust_city"));
                 customers.add(cust);
             }
        }catch(Exception e) {
            e.printStackTrace();
        }finally{
        }
    }
    
    private void sendCusomer(HttpServletResponse response) throws ServletException, IOException{
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        PrintWriter writer = response.getWriter();
        writer.print("<!DOCTYPE html><html lang='en'><head><meta charset='utf-8' ><title>Customers</title></head>"
                + "<body><h2>Customerss </h2>");
        for(Customer customer : customers) {
            writer.println("<li>" + customer.getName() +
                    "(" + customer.getCity() + ") (" +
                    "<a href='editCustomer?id="+ customer.getId() //当用户点击<a>标签 URL 会调用doGet()
                    + " '>edit )</a> </li>");
        }
        
        writer.println("<ul>");
        writer.println("</body></html>");
    }
    
     private Customer getCustomer(int cust_id) {
            for (Customer cust : customers) {
                if (cust.getId() == cust_id)
                    return cust;
            }
            return null;
        }
        
    private void sendEditCustomerForm(HttpServletRequest request,HttpServletResponse response)
                    throws ServletException, IOException{
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        PrintWriter writer = response.getWriter();
        int cust_id = 0;
        try {
            cust_id = Integer.parseInt(request.getParameter("id"));
        }catch(NumberFormatException e) {
            
        }
        Customer customer = getCustomer(cust_id);
        if ( customer != null) {
            writer.println("<!DOCTYPE html> <html lang='en' ><head>"
                    + "<meta  charset='UTF-8' >"
                    + "<title>Edit Customer</title></head>"
                    + "<body><h2>Edit Customer</h2>"
                    + "<form method = 'post' "
                    + "action = 'updateCustomer'>");
            /* hidden 定义隐藏字段 */
            writer.println("<input type='hidden' name='id' value='"
                    + cust_id + "' />" );
            writer.println("<table>");
            writer.println("<tr><td>name: </td><td>"
                    + "<input name='name' value= '"
                    + customer.getName()
                    + "'</td></tr>");
            writer.println("<tr><td>city: </td><td>"
                    + "<input name='city' value= '"
                    + customer.getCity()
                    + "'/></td></tr>");
            writer.println("<tr>"
                    + "<td colspan='2    ' style='text-algin:right'>"
                    // 当点击提交submit  会将隐藏(hddien) 的键对值发送给doPost
                    + "<input type='submit' value='Update' /></td>"
                    + "</tr>");
            
            writer.println("<tr>"
                    + "<td colspan='2    '>"
                    + "<a href='customer'>Customer List</a></td>"
                    + "</tr>");
            writer.println("</table></form></body></html>");
        }else
            writer.println("No customer found");
    }
    
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        String uri = request.getRequestURI();
        if(uri.endsWith("/customer")) {
            sendCusomer(response);
        }else if (uri.endsWith("/editCustomer"))
            sendEditCustomerForm(request,response);
    }
    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //update customer
        request.setCharacterEncoding("UTF-8");
        int cust_id = 0;
        try {
            cust_id=Integer.parseInt(request.getParameter("id"));
        }catch(NumberFormatException e) {
            
        }
        Customer cust = getCustomer(cust_id);
        if (cust != null) {
            cust.setName( request.getParameter("name"));
            cust.setCity(request.getParameter("city"));
        }
        sendCusomer(response);
    }
    
}

三.Cookies

cookies 是一个很少的信息片段,可以自动的在浏览器和Web服务器间交互,因此cookies可存储在多个页面间传递的信息,Cookies 作为HTTP协议的一部分,其传输协议是有HTTP协议控制.浏览器通常支持每个网站高达20个Cookies

Cookies的问题在于,用户可以通过改变浏览器的设置拒绝接受Cookies

Cookies的构造方法:

javax.servlet.http.Cookie cookie = new javax.servlet.http.Cookie(name, value);//通过给定键值对构造

要将cookie发送到浏览器需要HttpServletResponse的addcookie方法

httpServeltResonse.addCookie(cookie)

浏览器在访问同一Web服务器时,会将之前收到的cookie以便发送

服务器若要提取浏览器提交的cookie,可以通过HttpServletRequest接口的getCookies的方法,该方法返回一个Cookie数组,如果没有Cookie则返回null

如下为查询名为maxRecords的cookie的示例

Cookie[] cookies = request.getCookies();
        Cookie maxRecordesCookie = null;
        if(cookies != null)
        {
            for(Cookie cookie : cookies)
            {
                if(cookie.getName().contentEquals(" maxRecordesCookie"))
                {
                     maxRecordesCookie = cookie;
                    break;
                }
            }
        }

要删除Cookie 只能创建一个同名的Cookie,并将maxAge属性设置为0,并添加到HttpServletRepsonse 接口中

public void test() {
        Cookie cookie = new Cookie("userName","");
        cookie.setMaxAge(0);
        response.addCookie(cookie);
    }

Servlet Cookie 方法

以下是在 Servlet 中操作 Cookie 时可使用的有用的方法列表。

序号	方法 & 描述
1	public void setDomain(String pattern) 该方法设置 cookie 适用的域，例如 runoob.com。
2	public String getDomain() 该方法获取 cookie 适用的域，例如 runoob.com。
3	public void setMaxAge(int expiry) 该方法设置 cookie 过期的时间（以秒为单位）。如果不这样设置，cookie 只会在当前 session 会话中持续有效。
4	public int getMaxAge() 该方法返回 cookie 的最大生存周期（以秒为单位），默认情况下，-1 表示 cookie 将持续下去，直到浏览器关闭。
5	public String getName() 该方法返回 cookie 的名称。名称在创建后不能改变。
6	public void setValue(String newValue) 该方法设置与 cookie 关联的值。
7	public String getValue() 该方法获取与 cookie 关联的值。
8	public void setPath(String uri) 该方法设置 cookie 适用的路径。如果您不指定路径，与当前页面相同目录下的（包括子目录下的）所有 URL 都会返回 cookie。
9	public String getPath() 该方法获取 cookie 适用的路径。
10	public void setSecure(boolean flag) 该方法设置布尔值，表示 cookie 是否应该只在加密的（即 SSL）连接上发送。
11	public void setComment(String purpose) 设置cookie的注释。该注释在浏览器向用户呈现 cookie 时非常有用。
12	public String getComment() 获取 cookie 的注释，如果 cookie 没有注释则返回 null。

http头信息中包含如下内容

HTTP/1.1 200 OK
Date: Fri, 04 Feb 2000 21:03:38 GMT
Server: Apache/1.3.9 (UNIX) PHP/4.0b3
Set-Cookie: name=xyz; expires=Friday, 04-Feb-07 22:03:38 GMT; 
                 path=/; domain=runoob.com
Connection: close
Content-Type: text/html

例: PreferenceServlet 展示了如何通过cookies来进行会话管理,改Servlet允许用户通过修改四个cookie值设定显示配置

package cookie;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
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 java.sql.*;

@WebServlet(name ="PreferenceServlet", urlPatterns = {"/preference"})
public class PreferenceServlet extends HttpServlet{
    private static final long serialVersionUID = 888L;
    public static final String MENU = 
            "<div style = 'background:#e8e8e8;"
            + "padding:15px'>"
            + "<a href='cookieClss'>Cookie class </a>&nbsp;&nbsp;"
            + "<a href='cookieinfo'>Cookie info </a>&nbsp;&nbsp;"
            + "<a href='preference'>preference</a>" + "</div>";
    @Override
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");
        PrintWriter writer = response.getWriter();
        writer.print("<html lang='en'>\r\n" + 
                "<head>\r\n" + 
                "<meta charset='UTF-8' />\r\n" + 
                "<title>Preference</title>\r\n" + 
                "<style>\r\n" + 
                "table{\r\n" + 
                "font-size:samll;\r\n" + 
                "background:WHILE;\r\n" + 
                "}\r\n" + 
                "</style>\r\n" + 
                "</head><body>"
                + MENU
                + "Please select the value below:\r\n" + 
                "<form method='post' action=\"\">\r\n" + 
                "    <table>\r\n" + 
                "        <tr>\r\n" + 
                "        <td>Title Font Size:</td>\r\n" + 
                "        <td><select name='titleFontSize' >\r\n" + 
                "        <option >large</option>\r\n" + 
                "        <option >x-large</option>\r\n" + 
                "        <option >xx-large</option>\r\n" + 
                "        </select>\r\n" + 
                "        </td>\r\n" + 
                "        </tr>\r\n" + 
                "        <tr>\r\n" + 
                "            <td>Title Style %26 Weight: </td>\r\n" + 
                "            <td><select name='titleStyleAndWeight' multiple>\r\n" + 
                "            <option >italic</option>\r\n" + 
                "            <option >bold</option>\r\n" + 
                "            </select>\r\n" + 
                "            </td>\r\n" + 
                "        </tr>\r\n" + 
                "        <tr>\r\n" + 
                "            <td>Max, Records in Table: </td>\r\n" + 
                "            <td><select name='maxRecords'>\r\n" + 
                "            <option >5</option>\r\n" + 
                "            <option >10</option>\r\n" + 
                "            </select></td>\r\n" + 
                "        </tr>\r\n" + 
                "        <tr>\r\n" + 
                "            <td rowspan=\"2\">\r\n" + 
                "            <input type=\"submit\" value=\"set\" />\r\n" + 
                "            </td>\r\n" + 
                "        </tr>\r\n" + 
                "    </table>\r\n" + 
                "</form>\r\n" + 
                "</body>\r\n" + 
                "</html>");
    }
    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
        request.setCharacterEncoding("UTF-8");
        // 得到浏览器发送的值
        String maxRecords = request.getParameter("maxRecords");
　　　　　// 得到多选select的数组值
        String[] titleStyleAndWeight = request.getParameterValues("titleStyleAndWeight");
    
        String titleFontSize =
                request.getParameter("titleFontSize");
        // 创建Cookie 并发送
        response.addCookie(new Cookie("maxRecords",maxRecords));
        response.addCookie(new Cookie("titleFontSize",titleFontSize));
        //delete titleFontWeight and titleFontStyle cookies first
        // delete cookie by adding a cookie with the maxAage = 0;
        Cookie cookie =  new Cookie("titleFontWeight","");
        cookie.setMaxAge(0);
        response.addCookie(cookie);
        
        cookie = new Cookie("titleFontStyle","");
        cookie.setMaxAge(0);
        response.addCookie(cookie);
        
        if(titleStyleAndWeight != null) {
            for( String style : titleStyleAndWeight) 
            {
                if(style.contentEquals("bold"))
                response.addCookie(new Cookie("TitleFontWeight","bold"));
                else if (style.contentEquals("italic")) 
                {
                response.addCookie(new Cookie("titleFontStyle","italic"));    
                }
            } 
        }
        
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");
        PrintWriter writer = response.getWriter();
        writer.println("<html lang='en'>\r\n" + 
                "<head>\r\n" + 
                "<meta charset='UTF-8' />\r\n" + 
                "<title>Preference</title>\r\n" + 
                "</head><body>"
                + MENU
                + "Please select the value below:\r\n" +
                "<br/><br/> Max. Records in Table: " + maxRecords
                + "<br/>Title Font Size: " + titleFontSize
                + "<br/>TitleFOnt Style & Weight: "
                );
        //titleStyleAnd Weight will be null if none of the options
        //was selected 
        if(titleStyleAndWeight != null) {
            writer.println("<ul>");
            for (String style : titleStyleAndWeight)
                writer.print("<li>" + style + "</li>");
            writer.println("</ul>");
        }
        writer.println("</body></html>");
    }
            
}

package cookie;
/*
 * 
 */
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
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 java.sql.*;

@WebServlet(name = "CookieClassServlet", urlPatterns = { "/cookieClass" })
public class CookieClassServlet extends HttpServlet{
    private static final long serialVersionUID = 837369L;
    
    private String[] methods = {
            "cone1","cone2","cone3","cone4","cone5","cone6","cone7","cone8","cone9",
            "cone10","cone11","cone12","cone13","cone14","cone15","cone16","cone17","cone18",
    };
    
    @Override
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
        Cookie[] cookies = request.getCookies();
        Cookie maxRecordsCookie = null;
        if(cookies != null)
        {
            for(Cookie cookie: cookies)
            {
                if(cookie.getName().contentEquals("maxRecords")) {
                    maxRecordsCookie = cookie;
                    break;
                }
            }
        }
        
        int maxRecords = 5;
        if (maxRecordsCookie !=null)
        {
            try {
                // 得到cookie的值
                maxRecords = Integer.parseInt(maxRecordsCookie.getValue());
            }catch(NumberFormatException e) {
                
            }
        }
        
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");
        PrintWriter writer = response.getWriter();
        writer.print("<!DOCTYPE html>\r\n" + 
                "<html lang=\"en\">\r\n" + 
                "<head>\r\n" + 
                "    <meta charset=\"UTF-8\">\r\n" + 
                "    <title>Cookie class</title>\r\n" + 
                "</head>\r\n" + 
                "<body>"
                + PreferenceServlet.MENU +
                "<div>Here are some of the methods in javax.servlet.http.Cookie\r\n" + 
                "    <ul>");
        for( int i =0; i<maxRecords; i++) 
            writer.print("<li>" + methods[i] + "</li>");
            
            writer.print("</ul>\r\n" + 
                    "    </div>\r\n" + 
                    "</body>\r\n" + 
                    "</html>");
        
    }
    
}

package cookie;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
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 java.sql.*;

@WebServlet(name = "CookieInfoServlet", urlPatterns = { "/cookieinfo" })
public class CookieInfoServlet extends HttpServlet{

    private static final long serialVersionUID = 3829L;
    
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
        // 得到cookies的数组
        Cookie[] cookies = request.getCookies();
        StringBuilder styles = new StringBuilder();
        if( cookies != null) {
            for(Cookie cookie : cookies)
            {
                String name = cookie.getName();
                String value =cookie.getValue();
                if ( name.equals("titleFontSize"))
                    styles.append("font-size: " + value + ":");
                else if ( name.equals("titleFontWeight"))
                    styles.append("titleFontWeight: " + value + ":");
                else if ( name.equals("font-weight"))
                    styles.append("font-weight: " + value + ":");
            }
        }
        styles.append("}");
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");
        PrintWriter writer = response.getWriter();
        writer.print("<!DOCTYPE html>\r\n" + 
                "<html lang=\"en\">\r\n" + 
                "<head>\r\n" + 
                "    <meta charset=\"UTF-8\">\r\n" + 
                "    <title>Styles.toString()</title>\r\n" + 
                "</head>\r\n" + 
                "<body>" + PreferenceServlet.MENU +
                "<div class=\"title\">Session management with cookies:\r\n" + 
                "    </div>");
        
        //cookies will be null if there's no cookie
        if ( cookies ==null) {
            writer.print("NO cookie in this http response"  );
        }
        else {
            writer.println("<br/> Cookies in this http response: ");
            for(Cookie cookie : cookies) {
                writer.println("<br /> " + cookie.getName() + ": "
                        + cookie.getValue());
            }
        }
        writer.println("</body>\r\n" + 
                "</html>");
    }

}

4. HttpSession 对象

所有会话跟踪技术中HttpSession 最强大, 一个用户有且只能由一个HttpSession对象,并且不会被用户访问到

HttpSession对象在用户第一次访问网站时自动创建,你可以通过调用HttpServletRequest的getSession()获取该对象,getSession() 有两个重载方法

HttpSession getSession()/// 返回当前的HttpSession,若没有则创建HttpSession
HttpSession getSession(Boolean create)// 返回当前的HttpSession,create值false时若没有则返回null,create值true时若没有则创建HttpSession,

可以通过HttpSession的setAttribute方法将值放入HttpSession

void setAttribute(java.lang.String name, java.lang.Object value)

放入HttpSession的值时存储在内存中的,因此不要放入太多对象

通过调用HttpSession的getAttribute方法可以取回之前放入的对象

java.lang.Object getAttribute(java.lang.String name)

HttpSession 还有一个非常有用的方法,会返回一个Enumeration对象来迭代访问保存在HttpSession中的值

java.util.Enumeration<java.lang.String> getAttributeName();

HttpSession 会生成唯一标识,并将该标识发送给浏览器,在后续的请求中浏览器会将标识提交给服务器

可以用HttpSession 的geId方法获取该标识

java.lang.String getId()

HttpSession的ivalidate()方法会强制会话过期,并清空保存的对象,

void getMaxInactiveInterval( ) //查看会话多久会过期,单位为秒
void setMaxInactiveInterval( int seconds) //设置其超时时间,若为0 则永不过期

例: ShoppingCartServet 为一个小的有4个商品的在线商城,用户可以将商品添加到购物车中,并可以查看购物车内容,Produc类定义了4个属性(id,name,description 和price),Shopping 有两个属性即 quantity 和Product

package app02a.httpSession;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
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(name = "ShoppingCartServlet", urlPatterns = {
"/products", "/viewProductDetails",
"/addToCart", "/viewCart" })
public class ShoppingCartServlet extends HttpServlet {
private static final long serialVersionUID = -20L;
private static final String CART_ATTRIBUTE = "cart";
private List<Product> products = new ArrayList<Product>();
private NumberFormat currencyFormat = NumberFormat
.getCurrencyInstance(Locale.US);
@Override
public void init() throws ServletException {
products.add(new Product(1, "Bravo 32' HDTV",
"Low-cost HDTV from renowned TV manufacturer",
159.95F));
products.add(new Product(2, "Bravo BluRay Player",
"High quality stylish BluRay player", 99.95F));
products.add(new Product(3, "Bravo Stereo System",
"5 speaker hifi system with iPod player",
129.95F));
products.add(new Product(4, "Bravo iPod player",
"An iPod plug-in that can play multiple formats",
39.95F));
}
@Override
public void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {
String uri = request.getRequestURI();
if (uri.endsWith("/products")) {
sendProductList(response);
} else if (uri.endsWith("/viewProductDetails")) {
sendProductDetails(request, response);
} else if (uri.endsWith("viewCart")) {
showCart(request, response);
}
}
@Override
public void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {
// add to cart
int productId = 0;
int quantity = 0;
try {
productId = Integer.parseInt(
request.getParameter("id"));
quantity = Integer.parseInt(request
.getParameter("quantity"));
} catch (NumberFormatException e) {
}
Product product = getProduct(productId);
if (product != null && quantity >= 0) {
ShoppingItem shoppingItem = new ShoppingItem(product,
quantity);
// 得到当前浏览器的HttpSession对象
HttpSession session = request.getSession();
@SuppressWarnings("unchecked")
List<ShoppingItem> cart = (List<ShoppingItem>) session
.getAttribute(CART_ATTRIBUTE);
if (cart == null) {
    //如果当前的HttpSession里没有cart 则添加cart
cart = new ArrayList<ShoppingItem>();
session.setAttribute(CART_ATTRIBUTE, cart);
}
cart.add(shoppingItem);
}
sendProductList(response);
}
private void sendProductList(HttpServletResponse response)
throws IOException {
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
writer.println("<html><head><title>Products</title>" +
"</head><body><h2>Products</h2>");
writer.println("<ul>");
for (Product product : products) {writer.println("<li>" + product.getName() + "("+ currencyFormat.format(product.getPrice())
+ ") (" + "<a href='viewProductDetails?id="+ product.getId() + "'>Details</a>)");
}
writer.println("</ul>");
writer.println("<a href='viewCart'>View Cart</a>");
writer.println("</body></html>");
}
private Product getProduct(int productId) {
for (Product product : products) {
if (product.getId() == productId) {
return product;
}
}
return null;
}
private void sendProductDetails(HttpServletRequest request,
HttpServletResponse response) throws IOException {
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
int productId = 0;
try {
productId = Integer.parseInt(
request.getParameter("id"));
} catch (NumberFormatException e) {
}
Product product = getProduct(productId);
if (product != null) {
writer.println("<html><head>"
+ "<title>Product Details</title></head>"
+ "<body><h2>Product Details</h2>"
+ "<form method='post' action='addToCart'>"
);
writer.println("<input type='hidden' name='id' "
+ "value='" + productId + "'/>");
writer.println("<table>");
writer.println("<tr><td>Name:</td><td>"
+ product.getName() + "</td></tr>");
writer.println("<tr><td>Description:</td><td>"
+ product.getDescription() + "</td></tr>");
writer.println("<tr>" + "<tr>"
+ "<td><input name='quantity'/></td>"
+ "<td><input type='submit' value='Buy'/>"
+ "</td>"
+ "</tr>");
writer.println("<tr><td colspan='2'>"
+ "<a href='products'>Product List</a>"
+ "</td></tr>");
writer.println("</table>");
writer.println("</form></body>");
} else {
writer.println("No product found");
}
}
private void showCart(HttpServletRequest request,
HttpServletResponse response) throws IOException {
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
writer.println("<html><head><title>Shopping Cart</title>"
+ "</head>");
writer.println("<body><a href='products'>" +
"Product List</a>");
HttpSession session = request.getSession();
@SuppressWarnings("unchecked")
List<ShoppingItem> cart = (List<ShoppingItem>) session
.getAttribute(CART_ATTRIBUTE);
if (cart != null) {
writer.println("<table>");
writer.println("<tr><td style='width:150px'>Quantity"
+ "</td>"
+ "<td style='width:150px'>Product</td>"
+ "<td style='width:150px'>Price</td>"
+ "<td>Amount</td></tr>");
double total = 0.0;
for (ShoppingItem shoppingItem : cart) {
Product product = shoppingItem.getProduct();
int quantity = shoppingItem.getQuantity();
if (quantity != 0) {
float price = product.getPrice();
writer.println("<tr>");
writer.println("<td>" + quantity + "</td>")
;
writer.println("<td>" + product.getName()
+ "</td>");
writer.println("<td>"
+ currencyFormat.format(price)
+ "</td>");
double subtotal = price * quantity;
writer.println("<td>"
+ currencyFormat.format(subtotal)
+ "</td>");
total += subtotal;
writer.println("</tr>");
}
}
writer.println("<tr><td colspan='4' "
+ "style='text-align:right'>"
+ "Total:"
+ currencyFormat.format(total)
+ "</td></tr>");
writer.println("</table>");
}
writer.println("</table></body></html>");
}
}

package app02a.httpSession;

public class Product {
private int id;
private String name;
private String description;
private float price;
public Product(int id, String name, String description, float price) {
this.id = id;
this.name = name;
this.description = description;
this.price = price;
}
public int getId() {
    return this.id;
}
public String  getName() {
    return this.name;
}
public String getDescription() {
    return this.description;
}

public float getPrice() {
    return this.price;
}
// get and set methods not shown to save space
}

package app02a.httpSession;

public class ShoppingItem {
private Product product;
private int quantity;
public ShoppingItem(Product product, int quantity) {
this.product = product;
this.quantity = quantity;
}

public Product getProduct() {
    return this.product;
}
public int getQuantity() {
    return this.quantity;
}
// get and set methods not shown to save space
}

posted @ 2019-04-06 21:17 江期玉阅读(218) 评论(0) 编辑收藏举报

刷新页面返回顶部

飞龙dragon

servlet 会话管理

一.URL　重写

二.隐藏域

三.Cookies

要将cookie发送到浏览器需要HttpServletResponse的addcookie方法

服务器若要提取浏览器提交的cookie,可以通过HttpServletRequest接口的getCookies的方法,该方法返回一个Cookie数组,如果没有Cookie则返回null

要删除Cookie 只能创建一个同名的Cookie,并将maxAge属性设置为0,并添加到HttpServletRepsonse 接口中

Servlet Cookie 方法

4. HttpSession 对象

公告

飞龙dragon

servlet 会话管理

一.URL 重写

二.隐藏域

三.Cookies

要将cookie发送到浏览器需要HttpServletResponse的addcookie方法

服务器若要提取浏览器提交的cookie,可以通过HttpServletRequest接口的getCookies的方法,该方法返回一个Cookie数组,如果没有Cookie则返回null

要删除Cookie 只能创建一个同名的Cookie,并将maxAge属性设置为0,并添加到HttpServletRepsonse 接口中

Servlet Cookie 方法

4. HttpSession 对象

公告

一.URL　重写