全文總結:
在讀取Cookie,然後操作時,除了getName(),getValue()外,不要妄圖得到其他信息,如下方法不會得到值的:
cookie.getMaxAge();
cookie.getDomain();
。。。
因爲,客戶端傳來的時候,就只剩下key和value了。
Java中的Cookie操作:
在Java中利用Serlvet或者JSP scriptlet可以向瀏覽器端寫入Cookie。
同樣,利用Servet或者JSP scriptlet 也可以讀取到 Cookie信息。
Servlet規範中的Cookie API 如下:
setMaxAge setPath setDomain等方法,可以對Cookie狀態進行控制;
同樣存在如下方法,可以獲得相應的狀態:
getMaxAge getPath getDomain等方法,可以對Cookie的狀態。
然後,問題來了:
讀取Cookie時,發現除了Cookie的key和value外,其他的信息都丟失了!!
原因很簡單:
Cookie從服務器端發送到客戶端時,信息是完整的;
Cookie從客戶器端發送到服務端時,信息只剩下key、value了。
(想想也明白,Domain不對的Cookie、Path不對的Cookie、過期的Cookie,客戶端是不會發送過來的。)
那爲什麼Java中提供了相應的get方法呢? 那個方法是在生成Cookie後,尚未發送到客戶端時,使用的。是“封裝”的體現吧 O(∩_∩)O~
案例說話:
寫入Cookie的Servlet
- package edu.xjtu.servlet;
- import java.io.IOException;
- import java.io.PrintWriter;
- 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 AddCookie extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- Cookie cookie01 = new Cookie( "site" , "JavaEye" );
- cookie01.setMaxAge(60 * 60 * 1 );
- cookie01.setPath("/" );
- Cookie cookie02 = new Cookie( "name" , "xiaolongfeixiang" );
- cookie02.setMaxAge(60 * 60 * 2 );
- cookie02.setPath("/servlet" );
- response.addCookie(cookie01);
- response.addCookie(cookie02);
- response.setContentType("text/html;charset=UTF8" );
- PrintWriter out = response.getWriter();
- out.println("<HTML>" );
- out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>" );
- out.println(" <BODY>" );
- out.println(" cookie寫入了" );
- out.println(" <a href='show'> 查看cookie </a>" );
- out.println(" </BODY>" );
- out.println("</HTML>" );
- out.flush();
- out.close();
- }
- }
package edu.xjtu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
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 AddCookie extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Cookie cookie01 = new Cookie("site","JavaEye");
cookie01.setMaxAge(60*60*1);
cookie01.setPath("/");
Cookie cookie02 = new Cookie("name","xiaolongfeixiang");
cookie02.setMaxAge(60*60*2);
cookie02.setPath("/servlet");
response.addCookie(cookie01);
response.addCookie(cookie02);
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.println(" cookie寫入了");
out.println(" <a href='show'> 查看cookie </a>");
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
讀取Cookie的Servlet
- package edu.xjtu.servlet;
- import java.io.IOException;
- import java.io.PrintWriter;
- 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 ShowCookie extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- Cookie[] cookies = request.getCookies();
- StringBuffer buffer = new StringBuffer();
- for (Cookie cookie : cookies){
- buffer.append(cookie.getName()).append(" : " ).append(cookie.getValue());
- buffer.append(" -- " ).append( " MaxAge : " +cookie.getMaxAge());
- buffer.append(" -- " ).append( " Path : " +cookie.getPath()).append( "<br/>" );
- }
- response.setContentType("text/html;charset=UTF8" );
- PrintWriter out = response.getWriter();
- out.println("<HTML>" );
- out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>" );
- out.println(" <BODY>" );
- out.println(" 讀取的Cookie:<br>" );
- out.println(buffer.toString());
- out.println(" </BODY>" );
- out.println("</HTML>" );
- out.flush();
- out.close();
- }
- }
package edu.xjtu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
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 ShowCookie extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Cookie[] cookies = request.getCookies();
StringBuffer buffer = new StringBuffer();
for(Cookie cookie : cookies){
buffer.append(cookie.getName()).append(" : ").append(cookie.getValue());
buffer.append(" -- ").append(" MaxAge : "+cookie.getMaxAge());
buffer.append(" -- ").append(" Path : "+cookie.getPath()).append("<br/>");
}
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
out.println(" 讀取的Cookie:<br>");
out.println(buffer.toString());
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
}
寫入Cookie的頁面 :
Response的信息如下:(信息齊全!!)
查看Cookie的頁面:(發現結果丟了一部分:)
看瀏覽器的Cookie :
Cookie: name 屬性都對着的
Cookie: site 屬性也都對着的
再看看網絡:(發現傳過來的Cookie都只有key-value了。所以那些狀態信息都丟失了!!)
驗證了前面的總結:
在讀取Cookie然後操作時,除了getName(),getValue()外,不要妄圖得到其他信息,如下方法不會得到值的:
cookie.getMaxAge();
cookie.getDomain();
。。。
因爲,客戶端傳來的時候,就只剩下key和value了。
感謝rentianchou,在解決他(她)提出的問題時,我做了這個實驗!!謝謝rentianchou