dayjavaweb之文件和課件so easy系列session教程

SoEasySessionSessionSession一般譯為會話，是解決Http協(xié)議的無狀態(tài)問題的方案，可以將一次會話中的數(shù)據(jù)在IDSessionIDSession信息，進行進一步地操作。在JavaEE中提供了javax.servlet.http.HttpSession接口，通過該接口可以將共享的數(shù)據(jù)內(nèi)容HttpSessionHttpSession直接翻譯成中文比較，一般都譯成時域。在計算機專業(yè)術(shù)語中，Session是指一個終端用戶與交互系統(tǒng)進行通信的時間間隔，通常指從進入系統(tǒng)到注銷退出系統(tǒng)之間所經(jīng)過的時間。具體到Web中的Session指的就是用戶在瀏覽某個時，從進入到關(guān)閉這個所經(jīng)過的這段時間，也就是用戶瀏覽這個所花費的時間。因此從上述的定義中我們可以看到，Session實Session的概念需要包括特定的客戶端，特定的服務(wù)器端以及不中斷的操作Session。起到交換數(shù)據(jù)包的作用機制，session在網(wǎng)絡(luò)協(xié)議（例如 net或FTP）中是非常重要的部分。維持需要依靠在傳輸數(shù)據(jù)中的高級別程序。例如，在瀏覽器和主機之間的HTTP傳輸中sessionIDSession Session 都是解決Http協(xié)議的無狀態(tài)問題，但是兩者之間還是存在一定區(qū)別的 數(shù)據(jù)在客戶端的瀏覽器內(nèi)存中或本地緩存文件中，Session數(shù)據(jù)在服務(wù)器端的數(shù)據(jù)安全性較低，Session數(shù)據(jù)安全性較高，Session數(shù)據(jù)在服務(wù)器端內(nèi)存中增多時，降低服務(wù)器端性能。而 ， 的數(shù)據(jù)最大是4KB，一個只能20個 。Session則沒有這個問Session在關(guān)閉瀏覽器時失效，而持 則可以更長有效時間總的來說，Session與 SessionSessionMethod ReturnstheobjectboundMethod Returnstheobjectboundwiththespecifiednameinthissession,ornullifnoobjectisboundunderthename.ReturnsanEnumerationofStringobjectscontainingthenamesofalltheobjectsboundtothissession. Removestheobjectboundwiththespecifiednamefromthis name, Bindsanobjecttothissession,usingthenameRequestHttpSessionHttpSessionHttpSessionsession=HttpSessionStringname=SessionSessionHttpSessionServletHttpSessionServletHttpSessionpublicclassFirstServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{HttpSessionsession=request.getSession(); }publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}publicpublicclassSecondServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{PrintWriterout=response.getWriter();HttpSessionsession=Stringname=}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}Webweb.xml<?xmlversion="1.0"encoding="UTF-<web-app 打開瀏覽器，在地址欄中輸入在地址欄中再輸入Session在JavaEE的javax.servlet.http.HttpSessionMethodReturnsthetimewhenthissessionwascreated,measuredinmillisecondsmidnightJanuary1,1970ReturnsastringcontainingtheuniqueidentifierassignedtothisReturnsthelasttimethesentarequestassociatedwiththissession,asthenumberofmillisecondssincemidnightJanuary1,1970GMT,andmarkedbythetimethereceivedtheReturnstheumtimeinterval,inseconds,thattheservletcontainerwillthissessionopenbetweenReturnstheServletContexttowhichthissessionInvalidatesthissessionthenunbindsanyobjectsboundtoReturnstrueifthedoesnotyetknowaboutthesessionorifthechoosesnottojointhesession. Specifiesthetime,inseconds,betweenrequestsbeforetheservletwillinvalidatethisStringgetId()longgetCreationTime()sessionlonggetLastAccessedTime()sessionisNew()sessionIdsession的intgetMaxInactiveInterval()session可以的最大不活動時間（秒30session30Tomcatsession1session1session就會被移除；voidinvalidate()：讓session失效！調(diào)用這個方被session失效，當session失效后，客戶端再次請求，服務(wù)器會給客戶端創(chuàng)建一個新的session，并在響應(yīng)中給客戶端新session的下面我們通過一個Servlet將上述中的一些方法進試這里理解性就好后面案例中用到ServletHttpSessionpublicclassThreeServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{DateFormatformatter=newSimpleDateFormat("yyyy-MM-ddCalendarcalendar=HttpSessionsession=request.getSession();}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}Webweb.xml<?<?xmlversion="1.0"encoding="UTF-<web-app" 打開瀏覽器，在地址欄中輸入ServletHttpSession對象的基本使用方法，到目前為止，ServletServletHttpServletRequest對象、ServletContextHttpSessionServletContext中的數(shù)據(jù)就可以共享；SessionSessionHttpSession對象實現(xiàn)了在多次會話中共享數(shù)據(jù)內(nèi)容，HttpSession對象底層到底是如何實現(xiàn)MyEclipseDebugrequest.getSession()Debug模式啟動Tomcat服務(wù)器，并對應(yīng)的Servlet，抓取獲取的Session內(nèi)容org.apache.catalina.session.StandardSessionTomcat服SessionID值。IEHttpWatchServletIEHttpWatch會發(fā)現(xiàn)客戶端向服務(wù)器端發(fā)送請求時，向服務(wù)器端發(fā)送了一 :JSESSIONID=0BD17B07E383FA86703B370560E823F2;Path=/11_session/;: 信息。進而可以總結(jié)出Session的實現(xiàn)原理如下：因為Session使用的是會話 ，所以當瀏覽器關(guān)閉后，Session會失效。重新打開瀏覽器對應(yīng)Servlet時服務(wù)器端會重新創(chuàng)建Session對象可以使用持 來延長Session的有效時間 通過Session的實現(xiàn)原理可以知道，Session的實現(xiàn)是基于的。如果瀏覽器禁用話，Session是否還是有效的呢？下面我們具體操作來看一看。打開IE瀏覽器的“工具”->“Internet選項”->“隱私”選項，所 這時重新啟動Tomcat服務(wù)器，對應(yīng)的ServletURLResponseencodeURL()URLStringStringurl=request.getRequestURI();url=response.encodeURL(url);response.getWriter().println("<ahref='"+url+打開瀏覽器，在對應(yīng)頁面中點擊禁用解決Session的問題，這種解決方案是具有理論意義的，但不具備實際意義。因為大部分的都是基于完成數(shù)據(jù)共享的例如京東或淘寶等如果瀏覽器禁用，Session關(guān)于SessioinSessionSessionSession Session信息過期時（Session30分鐘SessionSessionJSP<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<%@page<%@page<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'show.jsp'starting<metahttp-equiv="pragma"content="no-<metahttp-equiv="cache-control"content="no-<metahttp-equiv="expires"<metahttp- "<metahttp-equiv="description"content="Thisismy商品列表Java編程思想<ahref="/11_session/show?id=1"></a><br>Java設(shè)計模式<ahref="/11_session/show?id=2"></a><br>Java語言<ahref="/11_session/show?id=3"></a><br>Oracle數(shù)據(jù)庫<ahref="/11_session/show?id=4"></a><br>MySQL數(shù)據(jù)庫<ahref="/11_session/show?id=5"></a><br>購物車記錄Map<String,Integer>map=if(map==Set<String>keySet=for(StringproductName:intnumber out.println("商品名稱："+productName+", 數(shù)量："+number+"<br/>");}}}ServletpublicclassShowServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{//獲 商品Stringid=獲得idString[]names={"Java編程思想","Java設(shè)計模式","Java語言 "Oracle數(shù)據(jù)庫","MySQL數(shù)據(jù)庫"};StringproductName=names[Integer.parseInt(id)-HttpSessionsession=request.getSession();Map<String,Integer>cart=(Map<String,Integer>)if(cart==null)cart=newHashMap<String,}//判 if(cart.containsKey(productName))intnumbercart.get(productName);cart.put(productName,number1);數(shù)量+1}else}//給用戶提示}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}ServletpublicpublicclassClearServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{HttpSessionsession=跳轉(zhuǎn)}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}}Webweb.xml<?xmlversion="1.0"encoding="UTF-<web-app 打開瀏覽器，在地址欄中輸入進試所謂一次，就是生成后，只能使用一次，不管成功或者失敗，都將失效。具JSP<%@pagelanguage="java"import="java.util.*"pageEncoding="UTF-<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.01<title>MyJSP'login.jsp'starting<scriptfunction ementById("myimg").src="/11_session/checkimg?timeStamp="+newDate().getTime();<h2style="color:red;">${requestScope.msg<formaction="/11_session/login"<td><inputtype="text"name="username" <td><inputtype="password"name="password"/> <td><inputtype="text"name="checkcode"/><imgsrc="/11_session/checkimg"onclick="change();"id="myimg"style="cursor:pointer;"/></td><tdcolspan="2"><inputtype="submit"value="登陸創(chuàng)建一個Servlet用于生成publicclassCheckImgServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{intwidth=intheight=BufferedImagebufferedImage=newBufferedImage(width,//步驟 繪制背景顏色通過繪圖對GraphicsgraphicsbufferedImage.getGraphics();//筆//繪制任何圖形之前都必須指定一個顏色graphics.setColor(getRandColor(200,250));graphics.fillRect(0,0,width,height);graphics.drawRect(0,0,width-1,height-1);Graphics2Dgraphics2d=(Graphics2D)graphics2d.setFont(newFont("宋體"Font.BOLD18));Stringwords= Randomrandom=newRandom();//生成隨機數(shù)//為了 StringBufferbuffer=new定義xintx=for(inti=0;i<4;i++)graphics2d.setColor(newColor(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));-3030intjiaodu=random.nextInt(60)-doubletheta=jiaodu*Math.PI/intindexrandom.nextInt(words.length());//生成隨機數(shù)0}

charc=將cgraphics2d.rotate(theta,x,graphics2d.drawString(String.valueOf(c),x,graphics2d.rotate(-theta,x,x+=// //步驟五繪制干擾線graphics.setColor(getRandColor(160,200));intx1;intx2;inty1;intfor(inti=0;i<30;i++){x1=random.nextInt(width);x2=random.nextInt(12);y1=random.nextInt(height);y2=random.nextInt(12);graphics.drawLine(x1,y1,x1+x2,x2+}//將上 輸出到瀏覽器ImageIO.write(bufferedImage,"jpg",}publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{doGet(request,}*@param@param@returnprivateColorgetRandColor(intfc,intbc)Randomrandom=newif(fc>255){fc=255;}if(bc>255){bc=255;}intr=fc+random.nextInt(bc-fc);intg=fc+random.nextInt(bc-fc);intb=fc+random.nextInt(bc-fc);returnnewColor(r,g,b);}}ServletpublicclassLoginServletextendsHttpServletpublicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOExcepti