15.html

写给JSP初级程序员的书

      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">架构可以充分利用用户原有的投资，如一些公司使用的</SPAN><SPAN 
      lang=EN-US>BEA Tuxedo</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
      lang=EN-US>IBM CICS, IBM Encina,</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">、</SPAN><SPAN 
      lang=EN-US>Inprise VisiBroker </SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">以及</SPAN><SPAN 
      lang=EN-US>Netscape Application Server</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。这之所以成为可能是因为</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">拥有广泛的业界支持和一些重要的‘企业计算’领域供应商的参与。每一个供应商都对现有的客户提供了不用废弃已有投资，进入可移植的</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">领域的升级途径。由于基于</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">平台的产品几乎能够在任何操作系统和硬件配置上运行，现有的操作系统和硬件也能被保留使用。</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><SPAN lang=EN-US><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></P>
      <P align=left class=MsoNormal 
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      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">能够保留现存的</SPAN><SPAN 
      lang=EN-US>IT</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">资产有以下三方面的好处：</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="mso-fareast-font-family: 楷体_GB2312"><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></B></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><B 
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      style="FONT-FAMILY: 楷体_GB2312; mso-ascii-font-family: 'Times New Roman'">应用程序能被利用</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="mso-fareast-font-family: 楷体_GB2312"><o:p></o:p></SPAN></B></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">已有的代码在</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">方案中可被重用，一个应用程序可重新划分层次而不用重写。这样就减少了开发时间，加快了进入市场的步伐，降低了开发成本，把项目保持在合理预算水平上。这同时也降低了企业的风险，因为公司可以使用已被验证和曾经运作的方案，而不是撤掉已有系统从新编写。</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><SPAN lang=EN-US><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 楷体_GB2312; mso-ascii-font-family: 'Times New Roman'">已有的产品和使用许可协议能被利用</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="mso-fareast-font-family: 楷体_GB2312"><o:p></o:p></SPAN></B></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如果一个公司已经购买了某些已有技术的使用许可协议或维护协议，如中间件，操作系统或硬件方面的许可协议，这些许可在</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">环境中仍能被使用。因此能够降低项目成本，缩短培训时间。</SPAN></P>
      <P align=left class=MsoNormal 
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      <P align=left class=MsoNormal 
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      style="mso-bidi-font-weight: normal"><SPAN 
      style="FONT-FAMILY: 楷体_GB2312; mso-ascii-font-family: 'Times New Roman'">对供应商的依赖性更小</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="mso-fareast-font-family: 楷体_GB2312"><o:p></o:p></SPAN></B></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">因为正在为你服务的供应商提供了用于</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">平台的产品，整体上只有一个供应商，你不需要依靠两个供应商的帮助在他们产品之间建立连接。这就减小了应用程序的复杂性，降低了整体风险水平。</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><SPAN lang=EN-US><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">与此相对照，微软的</SPAN><SPAN 
      lang=EN-US>WINDOWS DNA </SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">架构要求客户购买并安装</SPAN><SPAN 
      lang=EN-US>WINDOWS 2000,</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">还有可能需要客户购买新的硬件。客户就没有机会使用原有供应商的许可或维护协议，增加了项目成本。</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><SPAN lang=EN-US><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">我们也应当看到</SPAN><SPAN 
      lang=EN-US>WINDOWS DNA </SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">确实提供了到用户已有系统的连接，可是客户使用这种连接要依靠两个供应商：微软和现在为你提供产品的供应商。仅用一个供应商的方案通常比两个供应商的连接方案更易管理，更可靠。</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="FONT-SIZE: 16pt; mso-bidi-font-size: 10.0pt"><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></B></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="FONT-SIZE: 16pt; mso-bidi-font-size: 10.0pt">3</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN 
      style="FONT-FAMILY: 宋体; FONT-SIZE: 16pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.0pt">保护未来的</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="FONT-SIZE: 16pt; mso-bidi-font-size: 10.0pt">IT</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN 
      style="FONT-FAMILY: 宋体; FONT-SIZE: 16pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.0pt">投资，适应变化</SPAN></B><B 
      style="mso-bidi-font-weight: normal"><SPAN lang=EN-US 
      style="FONT-SIZE: 16pt; mso-bidi-font-size: 10.0pt"><o:p></o:p></SPAN></B></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">今天，一个公司的</SPAN><SPAN 
      lang=EN-US>IT</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">部门的灵活性与适应性是保持公司在市场中的竞争优势的源泉。公司应迅速改进程序，以期对变化的市场环境做出反应，同时公司通过更短时间内面向市场，比竞争对手更快的采取应对措施可以在竞争中取得飞跃。通过设计能够适应更多的用户负载或事务需求的商务系统，</SPAN><SPAN 
      lang=EN-US>IT</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">部门能够按照市场需求规划部署。</SPAN></P>
      <P align=left class=MsoNormal 
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      <P align=left class=MsoNormal 
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      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">能让一个公司具有更强的适应变化的能力。因为每一个基于</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">平台的产品都保证支持最基本的</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">服务。公司可以只需构造一次编码良好，符合</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的程序，然后在部署时按应用环境做出决策。如果底层平台的功能、伸缩性或可用性还不足以满足新的市场需求，用户可以有其他选择。如果客户的</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">应用程序设计良好，并能符合标准，这个系统可以随着时间的推移通过更换底层中间件、操作系统或硬件来进行放缩，却不会显著地更动应用程序。用这种方式对未来</SPAN><SPAN 
      lang=EN-US>IT</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">投资的保护是很具吸引力的建议。对市场需求的反应时间缩至最短，可以让公司以</SPAN><SPAN 
      lang=EN-US>INTERNET</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">所要求的那种速度采取行动。</SPAN></P>
      <P align=left class=MsoNormal 
      style="TEXT-ALIGN: left; mso-layout-grid-align: none"><SPAN lang=EN-US><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></SPAN></P>
      <P align=left class=MsoNormal 
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      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">而</SPAN><SPAN 
      lang=EN-US>WINDOWS DNA</SPAN><SPAN 
      style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">没有提供象</SPAN><SPAN 
      lang=EN-US>J2EE</SPAN><SPAN