外文翻譯-----使用開(kāi)放源碼工具的專業(yè)便攜式開(kāi)發(fā)

1、<p>　　Professional Portal Development with Open Source Tools</p><p>　　Design Pattern Considerations in Your Portal Clearly, there are many ways to implement a design that cannot be expressed adequately

2、in this chapter alone. Hopefully, the introduction of high-level pattern constructs and brief discussion of the implementation of Java standards in this chapter can facilitate your design decisions on your portal deploym

3、ents.</p><p>　　Java language and implementation standards can also help control complexity so that consistent levels of quality can be attained in your development activities. This in turn can lead to increa

4、sed partner adoption and portlet maintenance. Last, the adoption of design patterns should be applied so that best practices are propagated in your portal deployment and development operations can be hastened.</p>

5、<p>　　Much has been written during the last few years about design patterns and their use in Java development,so rather than go into great elaboration of their use, we felt that it would be more beneficial to provi

6、de high-level concepts of patterns that might be used in your portal deployments and to encourage you to explore them from the online Javaworld newsletter and from the Core J2EE Patterns book [ALUR].</p><p>

7、　　Planning for Portal Deployment</p><p>　　Using Java Standards</p><p>　　For many mission-critical development portal efforts, decisions need to be made about expensive software procurements to s

8、atisfy your development needs. In order to protect this investment, it is wise to consider standards when you make your purchasing decision because there is nothing worse than dumping a lot of money into a particular fra

9、mework only to learn after you have obtained it that it is a closed, proprietary system that does not work well with other systems. To guarantee that this doe</p><p>　　Figure 7.21 illustrates some of the Jav

10、a standards that could be considered for portal development. It is important to remember that these need to be established prior to procuring a portal framework or integrating existing applications into a homegrown porta

11、l application. Always be cognizant of the latest versions of the standards listed in Figure 7.21, and the effects that newer versions of those standards might have on your design decisions.</p><p>　　Figure 7

12、.21</p><p>　　Figure 7.22 illustrates some of the portal standards that should be considered before building your portalapplication.</p><p>　　On many portal implementations, a business case for a

13、dherence to language standards that relate to individual portlets needs to be made so that proprietary extensions are not adopted by a program that disallows code reuse and promotes vendor lock-in. Being exposed to propr

14、ietary data formats, one inevitably gets increasingly locked into the solutions of a particular vendor, which in turn limits the options for application software. This ultimately enables vendors to dictate enhancement pr

15、ices an</p><p>　　Figure 7.22</p><p>　　Model-View-Controller (MVC) Pattern</p><p>　　In the portal architecture shown in Figure 7.23, the MVC Pattern is where the servlet controller r

16、enders different views to the portal façade from a disparate set of data sources.</p><p>　　The model is the piece that has no specific knowledge of its controllers or its views. The portal system mainta

17、ins relations between the different models and views and broadcasts content to the views when the model changes state. The view is typically the piece that manages the visualizations of the model data. The controller is

18、the piece that manages user interaction with the model data.</p><p>　　The MVC Pattern is used with many frameworks because of its ability to handle content delivery complexities that are prominent in many en

19、terprise systems. Jakarta’s Struts and BEA’s WebFlow are two notable implementations that use this in their frameworks.</p><p>　　Template Method Pattern</p><p>　　A good practice when developing

20、JavaBeans in your portal applications is to use the Template Method Pattern [GoF] to enforce a common design across the portal back-end. The Template Method Pattern can be used so that modifications to your get and/or se

21、t methods will not affect your presentation view.</p><p>　　In the portal display in Figure 7.23, the JavaBean applications on the back-end implement the Template Method Pattern to manage the logic in the acc

22、essor (get/set) methods.</p><p>　　Memento Pattern</p><p>　　In the sample portal visualization shown in Figure 7.23, the view labeled #4 indicates that a form will be rendered to the user display

23、. In many cases, the form will use JavaScript to perform validation testing so that activities will be performed on the client side in order to alleviate unnecessary operations on the server. This is a good practice for

24、some Web applications, especially portals that perform heavy server operations, but sometimes incompatibilities in browsers allow inconsistent be</p><p>　　The Memento Pattern [GoF] will persist the state of

25、the form entries so that submits retain that data in the form text fields, and can perform server-side validation operations on that data.</p><p>　　Facade Pattern</p><p>　　The Façade Patter

26、n [GoF] is used in the portal application shown in Figure 7-23 to facilitate tedious operations that are associated with a database connection. Some of the operations that would warrant the use of a façade include t

27、he following: database connection handling, driver setups, and SQL statement construction.</p><p>　　Adapter Pattern</p><p>　　The Adapter Pattern [GoF] could be applied in the aforementioned port

28、al application as a means to rewrite legacy code implementations to share data from the back-end data stores. By wrapping existing code with an object adapter, the application can support existing interfaces by adapting

29、the interface of the parent class.</p><p>　　The Adapter Pattern provides a mechanism to convert one interface into another. This is necessary when a newer interface has superceded an older one. Instead of re

30、coding the implementation of the older interface, that implementation can be wrapped by an adapter that implements the newer interface. Calls to the new interface methods are then translated into calls to the older inter

31、face methods. This enables the legacy code to be extended to allow for more functionality, without having to rewrite </p><p>　　Factory Method Pattern</p><p>　　The Factory Method Pattern [GoF] ca

32、n be used to instantiate objects, such as a factory, by abstracting the creation and initialization of these objects from the user. This enables the client to focus on the application without being concerned with the obj

33、ect creation details. In our sample portal display, it can be used to generate a taxonomy object (from an XML file) that will generate queries as the user traverses the navigation tree.</p><p>　　Singleton Pa

34、ttern</p><p>　　The Singleton Pattern [GoF] ensures that only one instance of a class is created, and provides a single point of access to an object. In the portal example shown in Figure 7-23 a Singleton can

35、 be used to open a database connection or to generate a navigation tree from an XML file.</p><p>　　Front Controller Pattern</p><p>　　The Front Controller Pattern [ALUR] is part of the J2EE Prese

36、ntation Tier Patterns library. The Front Controller Pattern is similar to the MVC Pattern, and is actually used within the context of it, but it differs in that no model, or data access component, is associated with it.

37、Referring to our sample portal shown in Figure 7-23, a Servlet controller is used to render different JSP views to the portal display.</p><p>　　Note the following important features of the Front Controller P

38、attern: It allows for the handling of requests in a centralized location, which facilitates maintenance, and can perform authorization checks without having to spread unnecessary logic across multiple applications.</p

39、><p>　　Intercepting Filter Pattern</p><p>　　The Intercepting Filter Pattern [ALUR] is another J2EE Presentation Tier Pattern that was introduced with the Servlet 2.3 specification. This Pattern all

40、ows for the pre-processing and post-processing of user requests, as well as the capability to alter response headers and data when processing requests.</p><p>　　In the portal display, the Intercepting Filter

41、 Pattern can be used to swap presentation views within a portlet, meaning that the data sent back from the back-end database can be processed to render data in XML format so that an XSL stylesheet can be applied to the d

42、ata to present a different user view.</p><p>　　Client-Side Processing</p><p>　　Client-side processing refers to the application processing done at the browser. All browsers have been enabled to

43、interpret scripting instructions that would usually be sent to the server. This activity reduces the load on the server’s back-end.</p><p>　　Sadly, many challenges are present in browsers because of inconsis

44、tencies in their adherence to scripting standards. One of the most troublesome problems with browsers is inconsistencies with their implementations of the Document Object Model (DOM). The DOM standard is used to access e

45、lements and attributes of a Web document. These inconsistencies force developers to increase their development efforts to support different browser incompatibilities. To work around this issue, some portal efforts </p

46、><p>　　JavaScript</p><p>　　Different Web browsers, and different versions of the same Web browser, will often treat the similar JavaScript documents slightly differently. This browser incompatibili

47、ty becomes a more salient issue the more your portal application applies it in its client-side processing. The trick to is to establish a JavaScript standard, and apply it across all of your portal applications that use

48、JavaScript. With all portal applications that use JavaScript, make sure you’re aware of your presentations whe</p><p>　　Always remember to propagate your proven scripting practices across your portal develop

49、ment efforts. One best practice to apply across your JavaScripting effort in your portal is to put your JavaScript source in a separate JavaScript (.js) file. When this is done, the JavaScript source can be referenced wi

50、th the script tag in the following manner: <script src=””>.</p><p>　　Server-Side Processing</p><p>　　According to the JSR-168 Portlet Specification, portlets share many of the same attribu

51、tes as servlet components.The following table compares the two Web components to highlight their commonalities and differences.</p><p>　　Figure 7.24 describes the request-handling operations that occur durin

52、g portlet processing in a portal that implements the JSR-168 Portlet Specification APIs. The portlet container processes the action initiated by the portal user first, and then renders the portlet fragments in no specifi

53、c order to refresh the user display.</p><p>　　Figure 7.24</p><p>　　Java Plug-ins</p><p>　　Java Plug-ins enable Web applications to supplant a browser’s default virtual machine so th

54、at more upto-date JVMs can be applied to that application. The Java Plug-in, which requires a one-time download,enables applications to be consistent in their operations by overriding browser inconsistencies.</p>

55、<p>　　The first time a Web browser encounters a Web page that specifies the use of the Java Plug-in, the browser must download and install the required files for proper operation. On most portals’ applications, a li

56、nk should be provided to show users where a plug-in can be obtained to run their application. After the Java.</p><p>　　Plug-in has been downloaded, subsequent invocations of Web pages that are reliant on the

57、 plug-in will retrieve it from the local hard drive when an applet component is rendered.</p><p>　　The implementation of applets and Java Plug-ins in your portal deployments typically needs stakeholder “buy-

58、in” prior to acceptance. This consideration needs to be addressed because of bandwidth and firewall issues that might prevent users from downloading the plug-in to access portlets that use them. To gain better clarity on

59、 the implementation of the Java Plug-in on your portal implementation with two of the most common browsers, Netscape and Internet Explorer, developers should refer to Sun’s</p><p>　　The intention of WSRP is

60、to facilitate the integration of Web applications through a standard set of Web service interfaces. A simple sequence of steps (shown in Figure 7.25) is performed when adding portlets through Web services in portals. Whe

61、n a user puts a portlet on one of the portal pages, the portal requests the creation of a corresponding portlet instance on the WSRP service’s side, by calling the createPortletInstance operation and obtaining a portlet

62、instance handle that it uses in sub</p><p>　　Figure 7.25</p><p>　　使用開(kāi)放源碼工具的專業(yè)便攜式開(kāi)發(fā)</p><p>　　門(mén)戶的模式設(shè)計(jì)與思考</p><p>　　顯然，有許多方法來(lái)完成這個(gè)設(shè)計(jì)，在這一章不能全部表述出來(lái)。我們希望，引進(jìn)高層次的模式構(gòu)建與淺談執(zhí)行Java的標(biāo)準(zhǔn)

63、，這一章可以促進(jìn)您的門(mén)戶網(wǎng)站設(shè)計(jì)部署。 Java語(yǔ)言和執(zhí)行標(biāo)準(zhǔn)，也可以幫助控制復(fù)雜度，使在您的開(kāi)發(fā)活動(dòng)中實(shí)現(xiàn)一致的水平質(zhì)量。這反過(guò)來(lái)可能導(dǎo)致更多的合作伙伴采納使用portlet維護(hù)。最后，通過(guò)使用設(shè)計(jì)模式最佳做法，可以加速您的門(mén)戶網(wǎng)站宣傳的部署和發(fā)展業(yè)務(wù)。 </p><p>　　很多人已書(shū)面在過(guò)去幾年中的設(shè)計(jì)模式中使用Java開(kāi)發(fā)，因此，我們不是要制訂它們的使用，我們認(rèn)為這將更有利于提供高層次的概念模式，可用于在

64、您的門(mén)戶網(wǎng)站的部署，并鼓勵(lì)你探討它們?cè)诰€Javaworld通訊和核心的J2EE模式的圖書(shū)[ALUR] 。</p><p><b>　　門(mén)戶部署規(guī)劃 </b></p><p><b>　　使用Java標(biāo)準(zhǔn) </b></p><p>　　對(duì)于許多發(fā)展門(mén)戶網(wǎng)站的關(guān)鍵任務(wù)，需要購(gòu)買(mǎi)昂貴的軟件以滿足發(fā)展的需要。為了保護(hù)這些投資，決定

65、購(gòu)買(mǎi)是明智的選擇，因?yàn)闆](méi)有什么比投入了很多錢(qián)才得到特定的框架再差的了，只有了解之后，您才能獲得它，這是一個(gè)封閉的專有不支持其他系統(tǒng)工作的系統(tǒng)。為了保證這不發(fā)生在你身上，你應(yīng)該熟悉的軟件標(biāo)準(zhǔn)和其他應(yīng)用框架。令人遺憾的是，在很大程度上依賴專有擴(kuò)展常常迫使你的項(xiàng)目雇用昂貴的專業(yè)知識(shí)，幫助您部署您的計(jì)劃與他們的框架。 圖7.21顯示一些門(mén)戶發(fā)展的Java標(biāo)準(zhǔn)。它重要的是要記住，這需要在建立之前，采購(gòu)門(mén)戶框架或整合現(xiàn)有框架應(yīng)用到本門(mén)戶設(shè)計(jì)中來(lái)。認(rèn)

66、識(shí)到最新版本標(biāo)準(zhǔn)列在圖7.21，新版本的這些標(biāo)準(zhǔn)的可能已在您的設(shè)計(jì)決策之中。 </p><p><b>　　圖7.21</b></p><p>　　圖7.22說(shuō)明一些門(mén)戶網(wǎng)站的標(biāo)準(zhǔn)，在您的門(mén)戶網(wǎng)站建設(shè)應(yīng)用程序時(shí)可以參考。 在許多門(mén)戶網(wǎng)站的實(shí)施，商業(yè)案例遵守語(yǔ)言的標(biāo)準(zhǔn)，涉及到個(gè)人門(mén)戶需要作出這樣專有Extensions沒(méi)有通過(guò)的程序禁用代碼重用，并促進(jìn)供應(yīng)商鎖定。受專有

67、的數(shù)據(jù)格式的限制，其中不可避免地會(huì)越來(lái)越多地被限制在某一特定的供應(yīng)商，而這反過(guò)來(lái)又限制了選擇應(yīng)用軟件。這最終使供應(yīng)商提高價(jià)格，并對(duì)您的系統(tǒng)介紹了一些不必要的風(fēng)險(xiǎn)。</p><p><b>　　圖7.22</b></p><p>　　模型視圖控制器（ MVC模式）模式 </p><p>　　在門(mén)戶網(wǎng)站的架構(gòu)如圖7.23，MVC模式在這里呈現(xiàn)了se

68、rvlet控制器以正面的門(mén)戶從不同的地方得到數(shù)據(jù)。該模型沒(méi)有任何具體的知識(shí)或控制器。當(dāng)模型變化狀態(tài)時(shí)，門(mén)戶網(wǎng)站系統(tǒng)可中支持兩個(gè)模型采取不同的模式和廣播內(nèi)容。認(rèn)為通常是一塊可視化管理的模式數(shù)據(jù)。該控制器是管理用戶交互模型數(shù)據(jù)。 在MVC模式用于許多框架，因?yàn)樗谠S多知名企業(yè)系統(tǒng)中有能力處理復(fù)雜的內(nèi)容傳輸。Jakarta的Struts和BEA的WebFlow是兩個(gè)使用這個(gè)框架著名的實(shí)現(xiàn)。</p><p>　　模板方法

69、模式 一個(gè)良好的習(xí)慣做法是在門(mén)戶應(yīng)用中創(chuàng)建JavaBeans是使用模板方法模式[ GoF ]執(zhí)行一個(gè)共同的設(shè)計(jì)穿過(guò)整個(gè)門(mén)戶后端。模板方法模式可以 用來(lái)使您得到或修改一套方法不會(huì)影響您的演示文稿查看。 在門(mén)戶網(wǎng)站中顯示圖7.23中，該Java組件應(yīng)用在后端執(zhí)行模板方法模式來(lái)管理邏輯的存取（獲取/設(shè)置）方法。 </p><p><b>　　紀(jì)念模式</b></p><p&g

70、t;　　門(mén)戶網(wǎng)站的抽樣可視化如圖7.23所示，標(biāo)簽＃4表明，一種形式將提供給用戶顯示。在許多情況下，將使用JavaScript形式進(jìn)行測(cè)試，以便驗(yàn)證這一活動(dòng)是否在客戶端，以減輕不必要的服務(wù)器運(yùn)行。對(duì)于某些Web應(yīng)用程序這是一個(gè)很好的做法，特別是門(mén)戶網(wǎng)站的服務(wù)器進(jìn)行重新啟動(dòng)，但有時(shí)不兼容的瀏覽器允許違反行為發(fā)生。該紀(jì)念模式[ GoF]將堅(jiān)持規(guī)定的形式，以便提出保留數(shù)據(jù)形式的文本字段，并可以執(zhí)行服務(wù)器端驗(yàn)證的數(shù)據(jù)業(yè)務(wù)。</p>

71、<p>　　門(mén)面模式 門(mén)面模式[ GoF ]中使用的門(mén)戶應(yīng)用如圖7.23，以促進(jìn)冗長(zhǎng)業(yè)務(wù)相關(guān)的數(shù)據(jù)庫(kù)連接。一些操作將使外觀包括以下內(nèi)容：數(shù)據(jù)庫(kù)連接處理，驅(qū)動(dòng)程序設(shè)置，和SQL語(yǔ)句構(gòu)建。 </p><p><b>　　適配器模式</b></p><p>　　適配器模式[ GoF ]可用于在上述門(mén)戶網(wǎng)站應(yīng)用的一種手段重寫(xiě)遺留代碼實(shí)現(xiàn)共享數(shù)據(jù)從后端數(shù)據(jù)存儲(chǔ)。包

72、括現(xiàn)有代碼的對(duì)象適配器，該應(yīng)用程序可以支持現(xiàn)有的接口適應(yīng)的界面父類(lèi)。適配器模式提供了一個(gè)接口轉(zhuǎn)換成另一接口的機(jī)制。新的接口取代舊的是必要的。而不是重新執(zhí)行舊的接口，可以說(shuō)，執(zhí)行結(jié)束的適配器，實(shí)現(xiàn)了新的接口。調(diào)用新接口的方法，然后翻譯成給老年人調(diào)用接口的方法。這使遺留代碼將擴(kuò)大到更多的功能，而不必重寫(xiě)現(xiàn)有的代碼。</p><p><b>　　工廠方法模式</b></p><

73、p>　　工廠方法模式[ GoF ]通過(guò)抽象這些對(duì)象的創(chuàng)建和初始化可以用來(lái)實(shí)例化這些對(duì)象，如一個(gè)工廠。這使客戶專注于應(yīng)用而不涉及對(duì)象創(chuàng)建的細(xì)節(jié)。門(mén)戶網(wǎng)站在我們的樣本顯示，它可以用來(lái)生成一個(gè)分類(lèi)對(duì)象（由一個(gè)XML文件） ，這個(gè)對(duì)象將產(chǎn)生查詢用戶遍歷導(dǎo)航樹(shù)。</p><p><b>　　單件模式</b></p><p>　　單件模式[ GoF ]確保只有一個(gè)實(shí)例類(lèi)被創(chuàng)

74、建，并提供了一個(gè)單一的點(diǎn)訪問(wèn)一個(gè)對(duì)象。在門(mén)戶如圖7.23單件可以用來(lái)從一個(gè)XMl文件中打開(kāi)數(shù)據(jù)庫(kù)連接或生成一個(gè)導(dǎo)航樹(shù)。 </p><p>　　前端控制器模式 前端控制器模式[ALUR]是J2EE的外觀層模式庫(kù)。該控制器模式類(lèi)似MVC模式，在實(shí)際使用的環(huán)境中，它不同于那種沒(méi)有任何模式或數(shù)據(jù)訪問(wèn)的組件，它的內(nèi)部是相互聯(lián)系的。我們的范例門(mén)戶如圖7.23所示，一個(gè)servlet控制器用來(lái)提供不同的JSP試圖用門(mén)戶網(wǎng)站來(lái)

75、顯示。請(qǐng)注意以下前端控制器模式的重要特點(diǎn)：它可以對(duì)維護(hù)和執(zhí)行授權(quán)檢查進(jìn)行集中處理而無(wú)需多個(gè)應(yīng)用程序。</p><p><b>　　截取過(guò)濾器模式</b></p><p>　　截取過(guò)濾器模式[ALUR]是介紹Servlet2.3規(guī)范的另一個(gè)J2EE的三層模式， 這種模式允許前處理和后處理的用戶要求，當(dāng)進(jìn)程需要時(shí)，能改變頁(yè)眉和數(shù)據(jù)處理。在門(mén)戶網(wǎng)站顯示，攔截過(guò)濾模式可以用

76、來(lái)交換意見(jiàn)，提交在一個(gè)portlet中，即發(fā)回的數(shù)據(jù)從后端數(shù)據(jù)庫(kù)可以處理，使數(shù)據(jù)保存在XML表中，這樣的XSL樣式表可以適用于當(dāng)前不同用戶觀點(diǎn)的數(shù)據(jù)。</p><p>　　客戶端處理 客戶端處理是指應(yīng)用處理工作在瀏覽器中，所有的瀏覽器能解釋發(fā)送到這個(gè)服務(wù)器的腳本命令。這項(xiàng)活動(dòng)將減少服務(wù)器的后端負(fù)載。 可悲的是，瀏覽器要堅(jiān)持不一樣的腳本語(yǔ)言標(biāo)準(zhǔn)，因而存在著許多挑戰(zhàn)，其中最棘手的問(wèn)題，瀏覽器與它的實(shí)現(xiàn)文檔對(duì)象模型

77、（ DOM ）不一致 。標(biāo)準(zhǔn)的DOM是用于訪問(wèn)網(wǎng)頁(yè)文件的元素和屬性的。這些不一致促使開(kāi)發(fā)者改進(jìn)他們的開(kāi)發(fā)產(chǎn)品以支持瀏覽器的不兼容。對(duì)于這個(gè)問(wèn)題，一些門(mén)戶網(wǎng)站采取在服務(wù)器后端進(jìn)行大量的數(shù)據(jù)處理的辦法。其他可行的措施包括允許數(shù)量有限的客戶端處理，以及引用其他開(kāi)發(fā)產(chǎn)品的最優(yōu)作法。</p><p><b>　　JavaScrip</b></p><p>　　在不同的Web瀏覽

78、器和同一Web瀏覽器的不同版本中，處理類(lèi)似JavaScript的文件常常略有不同。當(dāng)網(wǎng)站應(yīng)用程序在其客戶端進(jìn)行處理的時(shí)候，瀏覽器不兼容成為一個(gè)更加突出的問(wèn)題。一個(gè)有效的方法是建立一個(gè)JavaScript的標(biāo)準(zhǔn)，并適用于所有的門(mén)戶網(wǎng)站應(yīng)用程序。所有的門(mén)戶應(yīng)用程序使用JavaScript ，在演示文稿時(shí)，確保 JavaScript在您的瀏覽器中被屏蔽。</p><p>　　永遠(yuǎn)記住實(shí)踐證明腳本在您的門(mén)戶網(wǎng)站的開(kāi)發(fā)中所

79、起的作用。 一個(gè)最佳的做法是在門(mén)戶網(wǎng)站上將你的JavaScript源代碼在一個(gè)單獨(dú)的JavaScript文件中。當(dāng)做到這一點(diǎn)， JavaScript的來(lái)源可以是引用的，腳本標(biāo)記方式如下： <script src=""> 。</p><p><b>　　服務(wù)器端處理</b></p><p>　　根據(jù)JSR – 168 的Portlet規(guī)范

80、，portlet許多相同的屬性的可以被servlet所共享。 下表把兩個(gè)Web組件作了比較，以突出其共性和分歧。</p><p>　　圖7.24描述了請(qǐng)求處理期間在portlet的門(mén)戶網(wǎng)站中發(fā)生的業(yè)務(wù)處理中實(shí)現(xiàn)了JSR – 168 Portlet規(guī)范的API 。在portlet容器進(jìn)程中首先運(yùn)行門(mén)戶網(wǎng)站，然后在portlet容器中的各個(gè)部分沒(méi)有具體的刷新顯示。</p><p><b&

81、gt;　　圖7.24</b></p><p>　　Java的插件 Java的插件使Web應(yīng)用程序取代瀏覽器默認(rèn)的虛擬機(jī)，使更多的JVMs可以適用于該應(yīng)用程序。該Java插件，需要一次性下載，使應(yīng)用程序通過(guò)重新定義不同的瀏覽器來(lái)保持它的一致性。最開(kāi)始的Web瀏覽器的網(wǎng)頁(yè)指定使用該Java插件，瀏覽器 必須下載并安裝正常運(yùn)行所需的文件。在多數(shù)門(mén)戶網(wǎng)站的應(yīng)用程序，鏈接應(yīng)當(dāng)向用戶展示一個(gè)可運(yùn)行的應(yīng)用程序插件

82、。java插件下載后，后面調(diào)用的web網(wǎng)頁(yè)的都是依賴插件的，當(dāng)一個(gè)applet組件提交時(shí)，該插件會(huì)從本地硬盤(pán)驅(qū)動(dòng)器得到需要的數(shù)據(jù)。 在門(mén)戶網(wǎng)站中執(zhí)行小應(yīng)用程序和Java插件通常需要支持之前的規(guī)定。由于考慮到帶寬和防火墻的問(wèn)題，可能用戶不能下載安裝插件來(lái)訪問(wèn)和使用portlet。為了更好地保證該Java插件可以在您的門(mén)戶網(wǎng)站執(zhí)行有兩個(gè)最常見(jiàn)的瀏覽器， Netscape和Internet Explorer ，開(kāi)發(fā)商應(yīng)提及Sun的Java插

83、件參考： http://java.sun.com/products/plugin/ 。</p><p>　　Web遠(yuǎn)程門(mén)戶服務(wù)（WSRP ）</p><p>　　Web遠(yuǎn)程門(mén)戶服務(wù)（WSRP ）是一種新技術(shù)，它將是一個(gè)重要JSR - 168規(guī)范的Portlet標(biāo)準(zhǔn)規(guī)格。它在即插即用的可視化界面的Web服務(wù)的門(mén)戶網(wǎng)站 或任何其他Web應(yīng)用程序中都可以使用。WSRP服務(wù)將允許提供商可以不改寫(xiě)

84、應(yīng)用程序曝光內(nèi)容或應(yīng)用程序。 </p><p>　　WSRP的意圖是通過(guò)一套標(biāo)準(zhǔn)的Web服務(wù)接口促進(jìn)一體化的網(wǎng)絡(luò)應(yīng)用程序，一個(gè)簡(jiǎn)單的步驟順序（如圖7.25所示 ）執(zhí)行在門(mén)戶網(wǎng)站上通過(guò)Web服務(wù)的增加portlet模塊。當(dāng)用戶將在一個(gè)門(mén)戶網(wǎng)站的網(wǎng)頁(yè)上增加一個(gè)porlet，門(mén)戶網(wǎng)站要求建立一個(gè)相應(yīng)的portlet來(lái)實(shí)例化WSRP服務(wù)，通過(guò)調(diào)用 createPortletInstance來(lái)取得的portlet實(shí)例

85、句柄以便以后的使用 。它可以從WSRP服務(wù)通過(guò)調(diào)用portlet內(nèi)的getPortletMarkup 操作和顯示的標(biāo)記獲取所需的標(biāo)記。如果獲得標(biāo)記含有鏈接或相關(guān)的窗體，當(dāng)用戶點(diǎn)portlet中的其中一個(gè)鏈接或窗體，portlet觸發(fā)相應(yīng)的WSRP服務(wù)performAction。當(dāng)門(mén)戶不再需要portlet實(shí)例了，就通過(guò)portlet實(shí)例上的WSRP服務(wù)調(diào)用destroyInstance 方法。對(duì)WSRP的執(zhí)行情況在www-106.ibm