JAVA网站制作之JSP构架

还有就是总有人问我到底该学习什么语言，什么语言有前途，那么我的回答是不论是C，C++，java，.net，ruby，asp或是其他语言都可以学，编程的关键不是语言，而是思想。js
--2种ModelI体例：和ModelIILanceLavandowska





blueski



编译：



　Servlet



假如你常常往或JSP的ModelI旧事组大概邮件列表，那末必定会看到很多关于和ModelII方OOP法的会商。事实接纳哪种，这取决于你的团体喜欢、团队事情战略和是不是接纳正统的。ModelI



复杂地说，将businesslogic事件逻辑（）presentationcode和暗示代码（）HTML交融在一同（如在中ModelII）；则倡始最年夜限制地将一切的代码放到内容暗示以外。ModelI





：简单的单条理使用Java



假如是在一团体人都精晓和HTML的HTML情况中，大概你单独做着一切的事情，假设每一个人都有明晰的编程布局和思绪，那末这类办法会很无效，不外如许的假定不在本文会商局限以内。这类办法的第一个长处是假如你的使用改动了，你只需保护一个文件。而最年夜的缺点是可读性！除非非常当心，不然你的和Java代码会互相混同，从而难以保护。TimeZone



鄙人面这个例子中，我们将增添一个元JSP素，从而使它酿成文TimeZone件，它会前往基于工夫的所等候的。TimeZone假如没有提交，那末缺省的是服务器的缺省工夫。



======================================================================xmlversion

<=1.0""?>H1

TimeJSP<H1>jsp

<:scriptlet>theparameter

//"zone"shallbeequaltoanumberbetween0and24(inclusive)TimeZonetimeZone

=TimeZone.getDefault();/returnsthedefaultTimeZonefortheserver/if

(request.getParameterValues(zone"")!null=)

{StringtimeZoneArg

=request.getParameterValues(zone""0)[];timeZone

=TimeZone.getTimeZone(GMT"+"+timeZoneArg+"00:");getsaTimeZone.Forthisexamplewe

//rejustgoingtoassumeitsapositiveargument

//,notanegativeone.

}sincewe

//rebasingourtimefromGMT,wellsetourLocaletoBrittania,andgetaCalendar.CalendarmyCalendar

=Calendar.getInstance(timeZone,Locale.UK);jsp

</:scriptlet>myCalendar.get

<%=(Calendar.HOUR_OF_DAY)%>:myCalendar.get

<%=(Calendar.MINUTE)%>:myCalendar.get

<%=(Calendar.SECOND)%>

======================================================================JavaBean

响应地，数据也能够从取得并加以显现。鄙人一个例子中我们就能够看到。ModelII





:重RedirectingRequests定向哀求（）HTML





在一个团队开辟情况中，有些是设Java计者，另外一些则是程Java序员，这时候这一办法显得十分主要。程HTML序员能够会合精神创立可重用代码，而设计师能够会合精神于内容暗示，相互绝对对峙，能够分离静态地修正本人的内容，只需整体的输出输入稳定。ModelII



如今我们可使用来ModelI暗示的Model-View-Controller谁人例子。这一办法遵守了(MVC)范例(citeDesignPatternsbook)。在servlet这个例子中，我们只要一个类(页大概)处Controller理哀求()TimeZone，获得，View设置一切用于暗示的变量，并将把持传送到暗示页()。作为云云复杂的使用，能够没有"Model"。Controller



:timeByZone.jspcontroller





可servlet所以一个或JSP一个页JSP。我保举利用，granularity由于如许我不用忧虑每当我做修正时要对类从头编译，可是，你将因而得到（颗粒性），今后要扩大该类也对照坚苦。





======================================================================xmlversion

<=1.0""?>--WorkerClass

<!,nobodyshouldseeme-->jsp

<:scriptlet>theparameter

//"zone"shallbeequaltoanumberbetween0and24(inclusive)TimeZonetimeZone

=TimeZone.getDefault();/returnsthedefaultTimeZonefortheserver/if

(request.getParameterValues(zone"")!null=)

{StringtimeZoneArg

=request.getParameterValues(zone""0)[];timeZone

=TimeZone.getTimeZone(GMT"+"+timeZoneArg+"00:");getsaTimeZone.Forthisexamplewe

//rejustgoingtoassumeitsapositiveargument

//,notanegativeone.

}TimeBeantimeBean

=newTimeBean();timeBean.setHours

=myCalendar.get(Calendar.HOUR_OF_DAY);timeBean.setMinutes

=myCalendar.get(Calendar.MINUTE);timeBean.setSeconds

=myCalendar.get(Calendar.SECOND);HttpSessionmySession

=request.getSession();mySession.putValue

(tempTimeBean""timeBean,);jsp



</:scriptlet>jsp

<:forwardpage=displayTime.jsp""/>

======================================================================View





:displayTime.jspview





一样地，这个既servlet能够是一个也jsp能够是一个文Session件。这里我们从中Bean获得并显现它的值。实践上我们会将这做两次，来树模是怎样被利用的。



======================================================================xmlversion

<=1.0""?>H1

TimeJSP<H1>jsp

<:useBeanclass=TimeBean""id=tempTimeBean""scope=session""/>jsp

<:getPropertyname=tempTimeBean""property=hours"">:jsp

<:getPropertyname=tempTimeBean""property=minutes"">:jsp

<:getPropertyname=tempTimeBean""property=seconds"">--thesewouldhaveprinted

<!"null"iftempTimeBeanwasnotinstantiatedbytimeByZone.jsp-->jsp



<:scriptlet>HttpSessionmySession

=request.getSession();TimeBeantimeBean

=mySession.getValue(tempTimeBean"");if

(timeBean!null=)

{/checktomakesureitsnotnull/,toavoidNullPointerExceptionsout.print

(timeBean.getHours());out.print

(":");out.print

(timeBean.getMinutes());out.print

(":");out.print

(timeBean.getSeconds());

}else



{out.println

(PressyourBackbuttonandselectaTimeZone"");

}jsp

</:scriptlet>

======================================================================null

第二种办法（在外部利用了代码）大概有些粗笨，但同意开辟者确保输入不至于很糟（比方":null:nullnull"Sessionbean)，假定还没有被实例化和没有举行值的设置。这View种情形产生在客户端间接挪用了页scriptlets。成绩是利用剧本可url以同意更强的把持。假如你确信你能够把持存bean取，那末方View法固然更合适于开辟，并使页HTML更便利于设计者的协同事情。ModelII





下面的是"传统的"设Session计。一切的变量都包装了并放在对2象中。这有个不敷：1



)如Session果客户端回绝介入的话，是不成失掉的。2



)除Session非变Session量被显式地移走，不然它回一向存在，直到被损坏或过时。cookies



第一种案例极可能产生在如许的场所，即便用了作mechanism为声明的布局（）form而开辟者没有可以供应声明的布局的替换表单（）URL，即改写。Sessions



第二个案例乃至更加严峻，由于它大概引发很年夜的内存损耗，假如被30界说为保留比尺度存留工夫更长的话（(尺度存留工夫是分30钟）。即便是分Session钟的，Model这类也Session大概在年夜的使用中引发劫难性的内存保守。为何呢？在对Session象外部设置的对象被实例化了，而且在终references止之前一向没有被移往。由于它们仍旧有联系关系（Session对象）指garbage-collected向它们，以是没法被渣滓搜集（）ModelII。在模Session型中，良多对象被放到中JavaBean（要末间接地，要末经由过程）Session。跟着的Session举行，更多的页被存取，内存利用会增添并延续下往直到客户端停止了或Session者过Session期。要一向比及变.得不法，放在那的对象才干被渣滓搜集，而那些丧失的内存本能够用于任何别的的用处。Beans



改善的办法之一是将或Request者别的变量放到对RequestDispatcher.include象中往，并利用(RequestDispatcher.forward)而不是(View)。如许做今后，页Controller具有和一ModelII样的存取哀求的对象。传统的设计的不敷能够被扫除。ModelII



一个最初的评注：只管有如上所述，我团体仍有些不喜好的典范，假如它用一般办法开辟的话。客户端被引送到某一个地点，然后又被转向到另外一个分歧的类，我不喜好创立如许的体系。基于如许的缘故原由，我修正了计划，使它酿成了以下的模样：Controller



:timeByZone2.jspcontroller





和后面一样，使Request用值View来获得需要的数据，而且将数据放到哀求的对象中往。这回的区分是页RequestDispatcher.include将利用(Controller)来挪用。chained在这类办法中，客户端不再做重定向，哀求不是"链接”class的。相称于/jsp请求了另外一方来为它做一些事情，然后持续。



======================================================================xmlversion

<=1.0""?>--WorkerClass

<!,nobodyshouldseeme-->jsp

<:scriptlet>theparameter

//"zone"shallbeequaltoanumberbetween0and24(inclusive)TimeZonetimeZone

=TimeZone.getDefault();/returnsthedefaultTimeZonefortheserver/if

(request.getParameterValues(zone"")!null=)

{StringtimeZoneArg

=request.getParameterValues(zone""0)[];timeZone

=TimeZone.getTimeZone(GMT"+"+timeZoneArg+"00:");getsaTimeZone.Forthisexamplewe

//rejustgoingtoassumeitsapositiveargument

//,notanegativeone.

}TimeBeantimeBean

=newTimeBean();timeBean.setHours

=myCalendar.get(Calendar.HOUR_OF_DAY);timeBean.setMinutes

=myCalendar.get(Calendar.MINUTE);timeBean.setSeconds

=myCalendar.get(Calendar.SECOND);request.setAttribute

(tempTimeBean""timeBean,);jsp

</:scriptlet>

======================================================================View





:displayTime2.jspdisplayTime.jsp





和非timeByZone2.jsp常类似，但在也的顶部被挪用。请注重<jsp:useBean/>中scope的""request已被换成了""。



======================================================================xmlversion

<=1.0""?>H1

TimeJSP<H1>jsp



<:includepage=timeByZone2.jsp""/>jsp



<:useBeanclass=TimeBean""id=tempTimeBean""scope=request""/>jsp

<:getPropertyname=tempTimeBean""property=hours"">:jsp

<:getPropertyname=tempTimeBean""property=minutes"">:jsp

<:getPropertyname=tempTimeBean""property=seconds"">--thesewouldhaveprinted

<!"null"iftempTimeBeanwasnotinstantiatedbytimeByZone2.jsp-->



======================================================================View





在一个在建体系中，我们已利用这类办法来创立类的链，每个都只对它所处置的事情卖力。经由过程分辨公用的暗示格局，我们创立了一个对JSP象，即便在很高条理的中它也能够反复利用。我们的方针就是创建一些可重用的页，同时削减用于暗示的类的数目。ServletModel



单个的(AModelIIDesign)





甚么时分我有充足工夫来研讨这个课题，我会在这里宣布更多的工具。



附原文：JSPArchitectures



Anexplanationandcomparisonofthemethodologies

commonlyknownas

"ModelI"and"ModelII".LanceLavandowskaToOutline

IfyouspendanytimereadingthroughServletorJSPrelatednewsgroupsormailinglists



,yourelikelytoencounteradiscussionofModelIversusModelIImethodologies.Whichoneyouusedependsonpersonaltaste,teamworkstrategiesandOOPorthodoxy.Looselydescribed



,ModelIisanapproachwherebusinesslogicandpresentationcodecanbeintermixedwiththepresentationitself(HTMLinourarena).ModelIIproscribesthatallcode,totheextentthisispossible,beexcludedfromthepresentation.ModelI



:Simple21/2TierApplicationInateamenvironmentwhereeveryoneknowsJavaandHTML

,orifyouredoingitallyourself,thisapproachcanworkwell,providedeveryonemaintainsaclearcodingstructure(thatdiscussionisoutsidetheboundsofthisarticle).Theprimaryadvantageofthisapproachisthatthereisonlyonefiletomaintainforchangestoyourapplication.Themajordisadvantageisreadability!Unlessgreatcareistaken,yourHTMLandJavacodecanbecomesointermingledthatitbecomesdifficulttodebugandmaintainyourapplication.Forthisexample



,wearegoingtorevisitthe"SamplePage"fromtheJSPQuickStartchapter.ImgoingtoaddaTimeZoneelement,sowellhaveaJSPthatreturnsthetimebasedonthedesiredtimezone.IfnoTimeZoneissubmitted,welldefaulttothatoftheserver.



======================================================================xmlversion

<=1.0""?>H1

TimeJSP<H1>jsp

<:scriptlet>theparameter

//"zone"shallbeequaltoanumberbetween0and24(inclusive)TimeZonetimeZone

=TimeZone.getDefault();/returnsthedefaultTimeZonefortheserver/if

(request.getParameterValues(zone"")!null=)

{StringtimeZoneArg

=request.getParameterValues(zone""0)[];timeZone

=TimeZone.getTimeZone(GMT"+"+timeZoneArg+"00:");getsaTimeZone.Forthisexamplewe

//rejustgoingtoassumeitsapositiveargument

//,notanegativeone.

}sincewe

//rebasingourtimefromGMT,wellsetourLocaletoBrittania,andgetaCalendar.CalendarmyCalendar

=Calendar.getInstance(timeZone,Locale.UK);jsp

</:scriptlet>myCalendar.get

<%=(Calendar.HOUR_OF_DAY)%>:myCalendar.get

<%=(Calendar.MINUTE)%>:myCalendar.get

<%=(Calendar.SECOND)%>

======================================================================Similarly

,thedatatobedisplayedcouldhavebeengottenfromaJavaBean.Wellseealittleofthatinthenextexample.ModelII

:RedirectingRequestsInateamenvironmentwheresomemembersareHTMLdesignersandothersareJavaprogrammers

,thisapproachcanbeparticularlystrong.TheJavaprogrammerscanfocusoncreating(re)usablecode,whiletheHTMLdesignerscanfocusonpresentation.Whilethetworemaindependantoneachother,oneortheothercanchangedramaticallysolongastheprincipleinputsandoutputs(respectively)remainthesame.Nowwe



lltakethesamedesiredbehaviourfromtheModelIexample,andpresentitusingtheModelIImethodology.ThismethodologyfollowstheModel-View-Controller(MVC)paradigm(citeDesignPatternsbook).Forthisexample,wellhaveoneclass(orpageorservlet)processtherequest(Controller)gettheTimeZone,,setalltherequiredvariablesforpresentation,andpasscontrolofftoapresentationpage(View).Forsimpleappslikethis,thereisno"Model".Controller



:timeByZone.jspThecontrollercanbeaservletorajspfile.IprefertouseJSP

,asIdonthavetoworryaboutcompilingtheclasseachtimeImakechanges.However,youlosegranularitythisway,andmakeitmoredifficulttoextendthisclasslater(wellreviewthisinAdvancedJSPProgramming).



======================================================================xmlversion

<=1.0""?>--WorkerClass

<!,nobodyshouldseeme-->jsp

<:scriptlet>theparameter

//"zone"shallbeequaltoanumberbetween0and24(inclusive)TimeZonetimeZone

=TimeZone.getDefault();/returnsthedefaultTimeZonefortheserver/if

(request.getParameterValues(zone"")!null=)

{StringtimeZoneArg

=request.getParameterValues(zone""0)[];timeZone

=TimeZone.getTimeZone(GMT"+"+timeZoneArg+"00:");getsaTimeZone.Forthisexamplewe

//rejustgoingtoassumeitsapositiveargument

//,notanegativeone.

}TimeBeantimeBean

=newTimeBean();timeBean.setHours

=myCalendar.get(Calendar.HOUR_OF_DAY);timeBean.setMinutes

=myCalendar.get(Calendar.MINUTE);timeBean.setSeconds

=myCalendar.get(Calendar.SECOND);HttpSessionmySession

=request.getSession();mySession.putValue

(tempTimeBean""timeBean,);jsp



</:scriptlet>jsp

<:forwardpage=displayTime.jsp""/>

======================================================================View

:displayTime.jspAgain

,theviewcanbeeitheraservletorajspfile.HerewellgettheBeanfromtheSession,anddisplayitsvalues.Wellactuallydothistwice,toillustrateagainhowBeansareused.





======================================================================xmlversion

<=1.0""?>H1

TimeJSP<H1>jsp

<:useBeanclass=TimeBean""id=tempTimeBean""scope=session""/>jsp

<:getPropertyname=tempTimeBean""property=hours"">:jsp

<:getPropertyname=tempTimeBean""property=minutes"">:jsp

<:getPropertyname=tempTimeBean""property=seconds"">--thesewouldhaveprinted

<!"null"iftempTimeBeanwasnotinstantiatedbytimeByZone.jsp-->jsp



<:scriptlet>HttpSessionmySession

=request.getSession();TimeBeantimeBean

=mySession.getValue(tempTimeBean"");if

(timeBean!null=)

{/checktomakesureitsnotnull/,toavoidNullPointerExceptionsout.print

(timeBean.getHours());out.print

(":");out.print

(timeBean.getMinutes());out.print

(":");out.print

(timeBean.getSeconds());

}else



{out.println

(PressyourBackbuttonandselectaTimeZone"");

}jsp

</:scriptlet>

======================================================================Thesecondmethod

(usingcodeinside)maybemorecumbersome,butallowsthedevelopertoensureagainstuglyoutput(suchas"null:null:nullnull"iftheSessionbeanhasnotbeeninstantiated)&haditsvaluesset.ThiswouldlikelyonlyhappeniftheclientsomehowcalledtheViewpagedirectly.Thepointisthatusingscriptletsallowsforgreatercontrol.Ifyouarecertainyoucancontrolurlaccess,thebeanapproachcertainlyeasesdevelopment,andmakestheViewpageeasierforHTMLdesignerstoworkwith.Theaboveisthe



"traditional"ModelIIdesign.YoullnotethatallthevariablesarewrappedupandplacedintotheSessionobject.Thishastwoweaknesses:1)noSessionisavailabebecausetheclienthasrefusedtoparticipate,2)unlesstheSessionvariableisexplicitlyremoveditwillcontinuetoexistuntiltheSessionisdestroyedorexpires.ThefirstcaseismostlikelytohappenwhencookiesareusedastheStatemechanismandthedevelopershavefailedtoprovideforthealternativeformofStatemaintenance



,URLrewriting.Thesecondcaseisevenmoreserious



,asitcanleadtogreatmemoryuseifSessionsaredefinedtoexistformorethanthestandardamountoftime(30minutesappearstobethestandard).Eveninthecaseof30minuteSessions,thisModelcanleadtodisastrousmemoryleaksinsystemsundergreatuse.Why?Objectsgetinstantiated,setinsidetheSessionobject,andarenotremoveduntiltheSessionends.Becausetheystillhavereferences(theSessionobject)pointingtothem,theyarenotgarbage-collected.IntheModelIIpattern,manyobjectsareplacedintotheSession(eitherdirectlyorviaaJavaBean).AstheSessionprogresses(morepagesareaccessed)memory-useincreasesandpersistsuntiltheclientendstheSessionortheSessiontimesout.UntiltheSessionisinvalidated,theobjectsplacedtherecannotbegarbage-collected,andthusconsumememorythatcouldbeofuseelsewhere.OnemeansofaddressingthisissueistoplacetheBeansorothervariablesintotheRequestobject



,anduseRequestDispatcher.include(ratherthanRequestDispatcher.forward)(.Bydoingso),theViewpagehasaccesstothesameRequestobjectastheController,andtheweaknessesofthetraditionalModelIIdesignareobviated.Onefinalcomment



:despitealltheabove,IhaveapersonaldistastefortheModelIIparadigmasitiscommonlyimplemented.Thecreationofasystemwheretheclientissenttoanaddress,butisredirectedtoadifferentclass,isforsomereasonabhorrenttome.Forthisreason,Ivemodifiedthedesigninthefollowingmanner:Controller



:timeByZone2.jspAsbefore

,thecontrollerusestheRequestvaluestoobtainthenecessarydataandputthatdataintotheRequestobject.ThedifferencethistimeisthattheViewpagewillcalltheControllerusingRequestDispatcher.include(.Inthisway),theclientisneverredirected,andRequestsarenot"chained".Rather,theclass/jspcalledaskssomeoneelsetodosomeworkforit,thencontinues.



======================================================================xmlversion

<=1.0""?>--WorkerClass

<!,nobodyshouldseeme-->jsp

<:scriptlet>theparameter

//"zone"shallbeequaltoanumberbetween0and24(inclusive)TimeZonetimeZone

=TimeZone.getDefault();/returnsthedefaultTimeZonefortheserver/if

(request.getParameterValues(zone"")!null=)

{StringtimeZoneArg

=request.getParameterValues(zone""0)[];timeZone

=TimeZone.getTimeZone(GMT"+"+timeZoneArg+"00:");getsaTimeZone.Forthisexamplewe

//rejustgoingtoassumeitsapositiveargument

//,notanegativeone.

}TimeBeantimeBean

=newTimeBean();timeBean.setHours

=myCalendar.get(Calendar.HOUR_OF_DAY);timeBean.setMinutes

=myCalendar.get(Calendar.MINUTE);timeBean.setSeconds

=myCalendar.get(Calendar.SECOND);request.setAttribute

(tempTimeBean""timeBean,);jsp

</:scriptlet>

======================================================================View

:displayTime2.jspMuchlikedisplayTime.jsp

,howeveryoullseethattimeByZone2.jspiscalledatthetopofthepage.Noticethatthescopeof<jsp:useBean/haschangedto>"request".



======================================================================xmlversion

<=1.0""?>H1

TimeJSP<H1>jsp



<:includepage=timeByZone2.jsp""/>jsp



<:useBeanclass=TimeBean""id=tempTimeBean""scope=request""/>jsp

<:getPropertyname=tempTimeBean""property=hours"">:jsp

<:getPropertyname=tempTimeBean""property=minutes"">:jsp

<:getPropertyname=tempTimeBean""property=seconds"">--thesewouldhaveprinted

<!"null"iftempTimeBeanwasnotinstantiatedbytimeByZone2.jsp-->



======================================================================Inasystemcurrentlyunderconstruction

,wevemadeuseofthismethodtocreatechainsofclasses,eachresponsibleforitsownprocessing.Byidentifyingcommonpresentationformats,wevecreatedViewobjectsthatcanbereusedinyethigherlevelJavaServerPages.Ourgoalistocreatepagesthataredesignedforreuse,andtoreducethenumberofpresentationclasses.SingleServletModel



(AModelIIDesign)WhenI

vehadtimetoadequatelyresearchandimplementthisidea,Illpostsomethinghere.


java比较简单,没有C++的烦琐,但学习时最好有C++为基础.与JSP和SQL起应用,功能强大.

Java自面世后就非常流行，发展迅速，对C++语言形成了有力冲击。Java 技术具有卓越的通用性、高效性、平台移植性和安全性，广泛应用于个人PC、数据中心、游戏控制台

至于JDBC，就不用我多说了，你如果用java编过存取数据库的程序，就应该很熟悉。还有，如果你要用Java编发送电子邮件的程序，你就得看看Javamail 了。

你一定会高兴地说，哈哈，原来成为Java高手就这么简单啊!记得Tomjava也曾碰到过一个项目经理，号称Java很简单，只要三个月就可以学会。

如果你学过HTML，那么事情要好办的多，如果没有，那你快去补一补HTML基础吧。其实JSP中的Java语法也不多，它更象一个脚本语言，有点象ASP。

[url]http://www.jdon.com/[/url]去下载，或到同济技术论坛的服务器[url]ftp://nro.shtdu.edu.cn[/url]去下，安装上有什么问题，可以到论坛上去提问。

自从Sun推出Java以来，就力图使之无所不包，所以Java发展到现在，按应用来分主要分为三大块：J2SE,J2ME和J2EE,这也就是Sun ONE(Open Net Environment)体系。J2SE就是Java2的标准版，主要用于桌面应用软件的编程；J2ME主要应用于嵌入是系统开发，如手机和PDA的编程；J2EE是Java2的企业版，主要用于分布式的网络程序的开发，如电子商务网站和ERP系统。

是一种简化的C++语言 是一种安全的语言，具有阻绝计算机病毒传输的功能

你可以去承接一些项目做了，一开始可能有些困难，可是你有技术积累，又考虑周全，接下项目来可以迅速作完，相信大家以后都会来找你的，所以Money就哗啦啦的。。。。。。

如果你学过HTML，那么事情要好办的多，如果没有，那你快去补一补HTML基础吧。其实JSP中的Java语法也不多，它更象一个脚本语言，有点象ASP。

还好，SUN提供了Javabean可以把你的JSP中的 Java代码封装起来，便于调用也便于重用。