request對象經常使用API 獲取請求參數的值 request應用 MVC設計模式

時間  2019-11-14
標籤 request 對象 經常 使用 api 獲取 請求 參數 應用 mvc 設計 模式 简体版
原文   原文鏈接

1 request對象經常使用API
  1)表示web瀏覽器向web服務端的請求
  2)url表示訪問web應用的完整路徑:http://localhost:8080/day06/Demo1
    uri表示訪問web應用的資源路徑:/day06/Demo1
    queryString表示?開頭的參數;name=jack
    pathInfo：路徑以外的信息，若是沒有，返回nullhtml

package cn.itcast.web.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/*
 * http://localhost:8080/day06/Demo1?name=jack回車
 */

public class Demo1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        /*
        String url = request.getRequestURL().toString();
        String uri = request.getRequestURI();
        String query = request.getQueryString();
        String pathInfo = request.getPathInfo();
        System.out.println("url=" + url);
        System.out.println("uri=" + uri);
        System.out.println("query=" + query);
        System.out.println("pathInfo=" + pathInfo);
        */
        
        String clientIP = request.getRemoteAddr();
        String clientHOST = request.getRemoteHost();
        int clientPORT = request.getRemotePort();
        
        String serverIP = request.getLocalAddr();
        String serverHOST = request.getLocalName();
        int serverPORT = request.getLocalPort();
        
        System.out.println("客戶端："+clientIP+":"+clientHOST+":"+clientPORT);
        System.out.println("服務端："+serverIP+":"+serverHOST+":"+serverPORT);
    }
}

得到客戶機信息java

    •getRequestURL方法返回客戶端發出請求時的完整URL。web

    •getRequestURI方法返回請求行中的資源名部分。正則表達式

    •getQueryString 方法返回請求行中的參數部分。apache

    •getPathInfo方法返回請求URL中的額外路徑信息。額外路徑信息是請求URL中的位於Servlet的路徑以後和查詢參數以前的內容，它以「/」開頭。編程

    •getRemoteAddr方法返回發出請求的客戶機的IP地址。設計模式

    •getRemoteHost方法返回發出請求的客戶機的完整主機名。瀏覽器

    •getRemotePort方法返回客戶機所使用的網絡端口號。緩存

    •getLocalAddr方法返回WEB服務器的IP地址。安全

    •getLocalName方法返回WEB服務器的主機名。

得到客戶機請求頭

    •getHeader(string name)方法:String

    •getHeaders(String name)方法:Enumeration

    •getHeaderNames()方法

得到客戶機請求參數(客戶端提交的數據)

    •getParameter(String)方法

    •getParameterValues（String name）方法

    •getParameterNames方法+BeanUtils框架
取得請求頭相關的信息
     *a)request.getHeader(String):String
      b)request.getHeaders(String):Enumeration
      c)getHeaderNames():Enumeration
*2 獲取請求參數的值
   2）取得請求體相關的信息
      a)request.getParameter(String):String
      b)request.getParameterValues(String):String[]
        注意：在GET請求方式下，若是參數不一致，返回null，可能出現空指針異常
      c)BeanUtils框架可以自動將String參數設置到JavaBean對象中
        1)無需理會參數的類型，個數，可是參數名必定要和JavaBean中的字段一致
        2)String->8種基本類型自動轉換，非8種基本類型能夠註冊轉換器
        3)String或String[]類型的參數自動感知裝配 

package cn.itcast.web.request;

import java.io.IOException;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        //一次性取得全部的請求頭信息
        Enumeration<String> enums = request.getHeaderNames();
        while(enums.hasMoreElements()){
            //key表示請求頭
            String key = enums.nextElement();
            Enumeration<String> enums2 = request.getHeaders(key);
            while(enums2.hasMoreElements()){
                String value = enums2.nextElement();
                response.getWriter().write(key+"<->"+value+"<br/>");
            }
        }
        
        /*
        String acceptLanguage = request.getHeader("Accept-Language");
        String userAgent = request.getHeader("User-Agent");
        String host = request.getHeader("Host");
        response.getWriter().write("Accept-Language=" + acceptLanguage + "<br/>");
        response.getWriter().write("User-Agent=" + userAgent + "<br/>");
        response.getWriter().write("Host=" + host + "<br/>");
        */
    }
}
package cn.itcast.web.request;

import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.InvocationTargetException;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.beanutils.BeanUtils;

import cn.itcast.web.domain.User;

/*
 * http://localhost:8080/day07/Demo2?username=jack&age=30&salary=5000&likes=dance&likes=sing回車
 */

public class Demo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        
        //分別取得客戶端提交的信息
        //String strUsername = request.getParameter("username");
        //String strAge = request.getParameter("age");
        //String strSalary = request.getParameter("salary");
        //String[] strLikes = request.getParameterValues("likes");
        
        BeanUtils bu = new BeanUtils();
        User user = new User();
        Enumeration<String> enums = request.getParameterNames();
        while(enums.hasMoreElements()){
            String key = enums.nextElement();
            String[] values = request.getParameterValues(key);
            try {
                bu.setProperty(user,key,values);
            }catch (Exception e) {
                e.printStackTrace();
            }
        }
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter pw = response.getWriter();
        pw.write("用戶名：" + user.getUsername() + "<br/>");
        pw.write("年齡：" + user.getAge() + "<br/>");
        pw.write("指望薪水：" + user.getSalary() + "<br/>");
        pw.write("愛好個數：" + user.getLikes().length + "<br/>");
        pw.flush();
        pw.close();
    }
}

*3 request應用
   1)防盜鏈
     判段某個頁面來自於何方，即referer請求頭

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>index.html</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
      <a href="/day07/DownServlet">下載</a>
  </body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>index.html</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
      這是廣告頁面
  </body>
</html>
package cn.itcast.web.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo4 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        
        //取得瀏覽器來自於何方
        String referer = request.getHeader("referer");
        
        //判段 
        if(referer!=null && referer.equals("http://localhost:8080/day07/index.html")){
            //轉發到download.html頁面
            this
                .getServletContext()
                .getRequestDispatcher("/download.html")
                .forward(request,response);
        }else{
            //轉發到ad.html頁面
            this
            .getServletContext()
            .getRequestDispatcher("/ad.html")
            .forward(request,response);
        }
    }
}

     2)收集表單數據
     a)項目中，用戶請求的參數，最好作null或空串的二次判段

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>index.html</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
      <form action="/day07/Demo5" method="post">
          <table border="1" align="center">
              <caption>用戶註冊</caption>
              <tr>
                  <th>用戶名</th>
                  <td><input type="text" name="username"/></td>
              </tr>
              <tr>
                  <th>密碼</th>
                  <td><input type="password" name="password"/></td>
              </tr>
              <tr>
                  <th>性別</th>
                  <td>
                      <input checked type="radio" name="gender" value="male"/>男
                      <input type="radio" name="gender" value="female"/>女
                  </td>
              </tr>
              <tr>
                  <th>愛好</th>
                  <td>
                      <input type="checkbox" name="likes" value="sing"/>唱歌
                      <input type="checkbox" name="likes" value="dance"/>跳舞
                      <input type="checkbox" name="likes" value="play"/>打球
                      <input type="checkbox" name="likes" value="net"/>上網
                  </td>
              </tr>
              <tr>
                  <th>上傳文件</th>
                  <td><input type="file" name="upfile"/></td>
              </tr>
              <tr>
                  <th>城市</th>
                  <td>
                      <select name="city">
                          <option value="bj">北京</option>
                          <option value="sh">上海</option>
                          <option value="gz" selected>廣州</option>
                          <option value="cq">重慶</option>
                      </select>
                  </td>
              </tr>
              <tr>
                  <th>留言</th>
                  <td>
                      <textarea name="message" rows="5" cols="20"></textarea>
                  </td>
              </tr>
              <tr>    
                  <td>
                      <input type="hidden" name="id" value="20111008"/>
                  </td>    
              </tr>                
              <tr>
                  <td colspan="2" align="center">
                      <input type="submit" value="提交"/>
                          &nbsp;&nbsp;&nbsp;&nbsp;
                      <input type="reset" value="重填"/>
                  </td>
              </tr>    
          </table>
      </form>
  </body>
</html>
package cn.itcast.web.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo5 extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        
        //將[請求體]的中文以UTF-8方式從新編碼
        request.setCharacterEncoding("UTF-8");

        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String gender = request.getParameter("gender");
        String[] likes = request.getParameterValues("likes");
        String upfile = request.getParameter("upfile");
        String city = request.getParameter("city");
        String message = request.getParameter("message");
        String id = request.getParameter("id");
        
        
        System.out.println("username="+username);
        System.out.println("password="+password);
        System.out.println("gender="+gender);
        System.out.println("likes="+likes.length);
        System.out.println("upfile="+upfile);
        System.out.println("city="+city);
        System.out.println("message="+message);
        System.out.println("id="+id);
    }
}

     3)中文亂碼
     a)POST方式下亂碼產生的緣由：瀏覽器發送的編碼方式與Request對象的編碼方式不一致
       解決方案：request.setCharacterEncoding("UTF-8)，該方法只能解析請求體中的亂碼方式，除此以外，無力解決
     b)若是用戶是post方式提交，在轉發狀況下，依然是post請求，但重定向狀況下，是get請求
     c)若是用戶是get方式提交，在轉發和重定向狀況下，都是get請求
     d)405：自己請求是get請求，但未在servlet內提供對應的doGet()方法, post也是相似  

針對請求頭編碼： 

<%@ page language="java" pageEncoding="UTF-8"%>
<%@ page import="java.net.*" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'get.jsp' starting page</title>
  </head>
  <body>
      <%-- 對中文編碼 --%>
    <a href="/day07/Demo7?username=<%=URLEncoder.encode("小王","UTF-8")%>">
        get方式傳中文
    </a>    
  </body>
</html>
package cn.itcast.web.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo7 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        
        String username = request.getParameter("username");
        
        //中文解碼
        byte[] buf = username.getBytes("ISO8859-1");
        username = new String(buf,"UTF-8");
        
        if(username!=null || username.trim().length()>0){
            response.setContentType("text/html;charset=UTF-8");
            response.getWriter().write("用戶名" + username);
        }
    }
}

//練習獲取ip地址和所屬地

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>用戶登陸</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
      <form action="/day07/LoginServlet" method="post">
          <table border="1" align="center">
              <caption>用戶登陸</caption>
              <tr>
                  <th>用戶名</th>
                  <td><input type="text" name="username"/></td>
              </tr>
              <tr>
                  <td colspan="2" align="center">
                      <input type="submit" value="提交"/>
                          &nbsp;&nbsp;&nbsp;&nbsp;
                      <input type="reset" value="重填"/>
                  </td>
              </tr>    
          </table>
      </form>
  </body>
</html>
package cn.itcast.web.request;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.itcast.web.domain.IpCheckBean;

public class LoginServlet extends HttpServlet {
    //key爲IP,value爲歸屬地
    private Map<String,String> map = new HashMap<String,String>();
    public void init() throws ServletException {
        //在用戶第一次訪問前加載IP和歸屬地，不存在多線程安全問題
        map.put("192.168.2.222","北京");
        map.put("192.168.10.122","上海");
        map.put("192.168.10.50","深圳");
        map.put("192.168.10.33","佛山");
        map.put("192.168.10.44","珠海");
        map.put("127.0.0.1","廣州");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        //IP
        String ip = request.getRemoteAddr();
        IpCheckBean ipCheckBean = new IpCheckBean();
        //歸屬地
        String address = ipCheckBean.check(ip,map);
        //用戶名
        String username = request.getParameter("username");
        //將信息綁定到ServletContext對象中
        ServletContext context = this.getServletContext();
        context.setAttribute("username",username);
        context.setAttribute("ip",ip);
        context.setAttribute("address",address);
        /*轉發到ShowServlet
        context
            .getRequestDispatcher("/ShowServlet")
            .forward(request,response);
        */
        //重定向到ShowServlet
        response.sendRedirect("/day07/ShowServlet");
    }
}
package cn.itcast.web.request;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletExceppackage cn.itcast.web.request;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ShowServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter pw = response.getWriter();
        pw.write("歡迎："+context.getAttribute("username")+"光臨<br/>");
        pw.write("你的IP是："+context.getAttribute("ip")+"<br/>");
        pw.write("歸屬地："+context.getAttribute("address")+"<br/>");
    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        this.doPost(request,response);
    }
}

lrequest對象實現請求轉發：請求轉發指一個web資源收到客戶端請求後，通知服務器去調用另一個web資源進行處理。請求轉發的應用場景：MVC設計模式

*4 再談MVC設計模式
   1)若是嚴格按照MVC思想的話，瀏覽器首頁訪問的是控制器，而後再由控制器轉發到視圖
   2)位於WEB-INF/目錄下的資源，客戶端沒法直接訪問，只能經過服務端轉發進入
   3)request對象也可用於資源的轉發
    request
        .getRequestDispatcher("/WEB-INF/success.html")
        .forward(request,response);
   4)經過正則表達式驗證中文：[\u4E00-\uFA29]+
   5)對於重定向而言，先後的二個Request域對象不一樣，若是取值不到，返回"null"，不會報錯   
 

   6)request對象提供了一個getRequestDispatcher方法，該方法返回一個RequestDispatcher對象，調用這個對象的forward方法能夠實現請求轉發。

   7)request對象同時也是一個域對象，開發人員經過request對象在實現轉發時，把數據經過request對象帶給其它web資源處理。

    •setAttribute方法

    •getAttribute方法

    •removeAttribute方法

    •getAttributeNames方法

package cn.itcast.web.request;

import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.itcast.web.domain.ModelBean;

public class Demo8 extends HttpServlet {
    //NO1
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        //轉發到view.html頁面
        RequestDispatcher rd = request.getRequestDispatcher("/WEB-INF/view.html");
        rd.forward(request,response);
    }
    //NO2
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String username = request.getParameter("username");
        ModelBean mb = new ModelBean();
        boolean flag = mb.validate(username);
        if(flag){
            //將用戶名綁定到Request域對象中
            request.setAttribute("USERNAME",username);
            
            /*轉發到ListServlet.java
            request
                .getRequestDispatcher("/ListServlet")
                .forward(request,response);
            */    
            
            //重定向到ListServlet.java
            response.sendRedirect("/day07/ListServlet");
            
        }else{
            request
            .getRequestDispatcher("/WEB-INF/fail.html")
            .forward(request,response);
        }
    }
}
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>用戶登陸</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
      <form action="/day07/Demo8" method="post">
          <table border="1" align="center">
              <caption>用戶登陸</caption>
              <tr>
                  <th>用戶名</th>
                  <td><input type="text" name="username"/></td>
              </tr>
              <tr>
                  <td colspan="2" align="center">
                      <input type="submit" value="提交"/>
                          &nbsp;&nbsp;&nbsp;&nbsp;
                      <input type="reset" value="重填"/>
                  </td>
              </tr>    
          </table>
      </form>
  </body>
</html>
package cn.itcast.web.request;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ListServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        String username = (String) request.getAttribute("USERNAME");
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write("歡迎"+username+"光臨");
    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        String username = (String) request.getAttribute("USERNAME");
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write("歡迎"+username+"光臨");        
    }
}
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>用戶登陸</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
    登陸失敗  
  </body>
</html>
package cn.itcast.web.domain;

public class ModelBean {
    public boolean validate(String username){
        boolean flag = false;
        if(username!=null && username.matches("[\u4E00-\uFA29]+")){
            flag = true;
        }
        return flag;
    }
}


5 request的細節
   1)轉發是經過RequestDispatcher對象的forward(request,response)方法完成的
   2)forward()方法以前的輸出，若是是輸出到緩衝區，再轉發到其餘Servlet，那麼原緩衝區的數據忽略不計
   3)forward()方法以前的輸出，若是真正輸出到瀏覽器，再轉發到其餘Servlet，再轉發到其餘Servlet代碼忽略不計
   4)forward()方法以前的輸出，若是是對響應頭的設置，會保留到轉發的其餘Servlet中

請求轉發的細節

    •forward方法用於將請求轉發到RequestDispatcher對象封裝的資源。

    •若是在調用forward方法以前，在Servlet程序中寫入的部份內容已經被真正地傳送到了客戶端，forward方法將拋出IllegalStateException異常。

    •若是在調用forward方法以前向Servlet引擎的緩衝區(response)中寫入了內容，只要寫入到緩衝區中的內容尚未被真正輸出到客戶端，forward方法就能夠被正常執

    •行，原來寫入到輸出緩衝區中的內容將被清空，可是，已寫入到HttpServletResponse對象中的響應頭字段信息保持有效

package cn.itcast.web.request;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo91 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        //response.setContentType("text/html;charset=UTF-8");
        //PrintWriter pw = response.getWriter();
        //pw.write("Demo91");
        //pw.flush();
        //pw.close();
        //request.getRequestDispatcher("/Demo92").forward(request,response);
        response.sendRedirect("/day06/success.html");
    }
}
package cn.itcast.web.request;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo92 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        response.getWriter().write("哈哈");
    }
}

 

*6 重定向和轉發區別

    •一個web資源收到客戶端請求後，通知服務器去調用另一個web資源進行處理，稱之爲請求轉發/307。

    •一個web資源收到客戶端請求後，通知瀏覽器去訪問另一個web資源進行處理，稱之爲請求重定向/302。
   1)轉發只能相對於當前web應用而言，不能轉發到其它web應用
     重定向能夠在當前web應用以外的其它web應用重寫向資源
   2)轉發/表示當前web應用
     重定向/表示web服務器的根目錄，即webapps目錄
   3)轉發時，瀏覽器地址欄不變
     重定向時，瀏覽器地址欄改變
   4)轉發是服務端的內部行爲，瀏覽器不知
     重定向是瀏覽器和服務端的共同行爲，瀏覽器必知
   5)轉發時二個Servlet共享request域對象
     重定向時二個Servlet獨享request域對象
   6)request具備二義性：
    a)請求對象
    b)域對   
7 include包含
   1)須要使用Servlet包含相同的頁面輸出時，相似於函數調用

    •RequestDispatcher.include方法用於將RequestDispatcher對象封裝的資源內容做爲當前響應內容的一部分包含進來，從而實現可編程的服務器端包含功能。

    •被包含的Servlet程序不能改變響應消息的狀態碼和響應頭，若是它裏面存在這樣的語句，這些語句的執行結果將被忽略

package cn.itcast.web.request;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo10 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        
        //取得客戶端請求的類型
        String method = request.getMethod();
        System.out.println("method="+method);
        
        
        //包含head.html(相似於函數調用)
        request
            .getRequestDispatcher("/common/head.html")
            .include(request,response);
        response.getOutputStream().write("<hr/>".getBytes());
        
        //動態生成
        response.getOutputStream().write("login.html".getBytes());
        response.getOutputStream().write("<hr/>".getBytes());
        
        //包含foot.html
        request
            .getRequestDispatcher("/common/foot.html")
            .include(request,response);
        response.getOutputStream().write("<hr/>".getBytes());
    }
}

會話
   1)用戶輸出URL地址，有效訪問某個網站，在該網站上的一系列有效操做，隨後關閉瀏覽器的整個過程，叫一次會話
   2)會話主要解決服務端如何保存每一個客戶端對應的私有信息。
   3)會話主要有二種：
    a)Cookie技術[客戶端技術]
    b)Session技術 
  
Cookie

image_thumb4_thumb
   1)Cookie是客戶端的技術
   2)每次發送請求時，客戶端都會帶上各自已的不一樣Cookie到服務端，服務端一解析Cookie，就知道是哪一個客戶端發送過來的信息
   3)一個Cookie只能存儲一種類型的信息
   4)更新某個名的Cookie，即向瀏覽器寫一個相同名的Cookie
   5)Cookie必定要設置一個有效時間，若是不設置的話，默認該請求訪問結束後，該Cookie自動銷燬，用專業名詞來說，
     Cookie的默認有效期時一個有效會話結束

package cn.itcast.web.cookie;

import java.io.IOException;
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 Demo1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        /*
        //服務端產生Cookie
        Cookie cookie = new Cookie("username","haha");
        //設置Cookie存活時間
        cookie.setMaxAge(1*24*60*60);
        //服務端將Cookie寫到客戶端暫存
        response.addCookie(cookie);
        */
        
        //取得客戶端全部的Cookie
        Cookie[] cookies = request.getCookies();
        Cookie usernameCookie = null;
        if(cookies!=null){
            for(Cookie c : cookies){
                if(c.getName().equals("username")){
                    usernameCookie = c;
                    break;
                }
            }
            //若是找到了Cookie
            if(usernameCookie!=null){
                System.out.println("Cookie的名字：" + usernameCookie.getName());
                System.out.println("Cookie的值：" + usernameCookie.getValue());
                System.out.println("Cookie的生命：" + usernameCookie.getMaxAge());
                System.out.println("Cookie的路徑：" + usernameCookie.getPath());
            }
        }
    }
}
package cn.itcast.web.cookie;

import java.io.IOException;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/*
 * http://localhost:8080/day07/Demo2?name=jack回車
 */
public class Demo2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        String name = request.getParameter("name");
        if(name==null){
            name="default";
        }
        
        //取得客戶端的全部Cookie的值
        Cookie[] cookies = request.getCookies();
        if(cookies==null){
            Cookie cookie = new Cookie("name_"+name,System.currentTimeMillis()+"");
            cookie.setMaxAge(1*24*60*60);
            response.addCookie(cookie);
            response.setContentType("text/html;charset=UTF-8");
            response.getWriter().write("歡迎"+name+"首次光臨,訪問時間：" + new Date().toLocaleString());
        }else{
            //查找名爲name的Cookie
            Cookie nameCookie = null;
            for(Cookie c : cookies){
                if(c.getName().equals("name_"+name)){
                    nameCookie = c;
                    break;
                }
            }
            //找到了
            if(nameCookie!=null){
                String strTime = nameCookie.getValue();
                response.setContentType("text/html;charset=UTF-8");
                long lastTime = Long.parseLong(strTime);
                response.getWriter().write("歡迎"+name+"再次光臨,你上次訪問時間：" + new Date(lastTime).toLocaleString());
                //更新時間
                Cookie cookie = new Cookie("name_"+name,System.currentTimeMillis()+"");
                cookie.setMaxAge(1*24*60*60);
                response.addCookie(cookie);
            }
        }
    }
}

 

*0 帶用驗證碼功能的用戶登陸
  1)驗證碼使用一個CheckCodeSerlvet產生，經過<img src=""/>發送請求，將驗證碼綁定到HttpSession中
  2)產生的驗證碼必定要在輸出到瀏覽器以前綁定到HttpSession中
  3)設置驗證碼禁止緩存要在輸出到瀏覽器以前 
  4)全部響應頭的設置放置在最早

package cn.itcast.web.session;

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class CheckCodeServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        response.setHeader("expires","-1");
        response.setHeader("cache-control","no-cache");
        response.setHeader("pragma","no-cache");
        String token = Token.getNum();
        //將驗證碼綁定到域對象
        HttpSession session = request.getSession();
        session.setAttribute("checkCodeServer",token);
        BufferedImage image = new BufferedImage(50,25,BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        g.drawString(token,15,15);
        //加干擾線
        for(int i=0;i<10;i++){
            Random r = new Random();
            int x1 = r.nextInt(50);
            int y1 = r.nextInt(25);
            g.drawLine(x1, y1, x1+4,y1+4);
        }
        ImageIO.write(image,"JPG",response.getOutputStream());
    }
}
class Token{
    public static String getNum(){
        Random r = new Random();
        int num = r.nextInt(10000);
        return num + "";
    }
}
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>login.html</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
      <form action="/day09/LoginServlet" method="post">
          <table border="1" align="center">
              <tr>
                  <th>用戶名</th>
                  <td><input type="text" name="username"/></td>
              </tr>
              <tr>
                  <th>密碼</th>
                  <td><input type="password" name="password"/></td>
              </tr>
              <tr>
                  <th>驗證碼</th>
                  <td>
                      <input type="text" name="checkCodeClient"/>
                  </td>
                  <td>
                      <img src="/day09/CheckCodeServlet"/>    
                  </td>
              </tr>
              <tr>
                  <td colspan="2" align="center">
                      <input type="submit" value="提交"/>
                  </td>
              </tr>
          </table>
      </form>
  </body>
</html>
package cn.itcast.web.session;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        //收集客戶端填入的驗證碼
        String checkCodeClient = request.getParameter("checkCodeClient");
        //取得服務端填入的驗證碼
        String checkCodeServer = (String) request.getSession().getAttribute("checkCodeServer");
        //判段
        response.setContentType("text/html;charset=UTF-8");
        if(checkCodeClient!=null && checkCodeClient.trim().length()>0 && checkCodeServer!=null && checkCodeServer.equals(checkCodeClient)){
            response.getWriter().write("驗證碼正確");
        }else{
            response.getWriter().write("驗證碼出錯");
        }
    }
}
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