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mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">开发一个</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">分布式应用程序的最后一步是部署应用程序并在其运行时监测企业级的计算和网络环境。以下就是这两个部署与运行角色：</span></p>
<p class="MsoNormal" style="margin-left:57.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo1;
tab-stops:list 57.0pt"><span lang="EN-US" style="font-family:
Wingdings">l</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">部署者（</span><span lang="EN-US">Deployer</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">）</span></p>
<p class="MsoNormal" style="margin-left:57.0pt"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">部署者懂得分布式应用程序的运行环境。他们利用容器提供者提供的工具来修改</span><span lang="EN-US">enterprise
beans</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">的属性以适应于目标运行环境。列如，部署者通过设置部署描述器中适当的属性来调整事务和安全特性。他们也将现成的企业级的管理软件集成进应用程序。</span></p>
<p class="MsoNormal" style="margin-left:57.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo1;
tab-stops:list 57.0pt"><span lang="EN-US" style="font-family:
Wingdings">l<span style="font:7.0pt "Times New Roman""> </span></span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">系统管理员（</span><span lang="EN-US">System
administrator</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">）</span></p>
<p class="MsoNormal" style="margin-left:57.0pt"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">一旦应用程序部署完毕，由系统管理员监测其运行情况，并且当其运行失常时采取适当措施。管理员负责为</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">服务器和容器提供企业级的计算和网络环境的配置和管理。</span><b><span lang="EN-US" style="font-size:12.0pt"> <o:p>
</o:p>
</span></b></p>
<hr>
<p><b><font color="#000080" size="3"><span lang="EN-US">EJB</span><span style="font-size:12.0pt;font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">体系结构</span></font><span lang="EN-US" style="font-size:12.0pt"><font color="#000080"><o:p>
</font>
</o:p>
</span></b></p>
<p class="MsoNormal"><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">多层的分布式应用程序通常由运行于本地的客户机，包含商业逻辑的运行于服务器上的中间层和由企业级的信息系统（</span><span lang="EN-US">EIS</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">）组成的后端三部分组成。一个</span><span lang="EN-US">EIS</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">可以是一个关系数据库，一个</span><span lang="EN-US">ERP</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">系统，一个传统应用程序或任何需要数据访问的数据储存库。下图展示了一个标准的</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">多层分布式应用程序，包含三层：客户端；部署容器和</span><span lang="EN-US">beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">的服务器；以及企业级的信息系统。</span></p>
<p class="MsoNormal"><span lang="EN-US">EJB</span><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">体系结构图</span></p>
<p class="MsoNormal"><img border="0" src="ejb_architecture.gif" width="675" height="561"></p>
<p class="MsoNormal"><span lang="EN-US"> <o:p>
</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">由于我们感兴趣的是怎样开发</span><span lang="EN-US">enterprise
beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">，所以我们把精力集中于中间层。</span></p>
<p class="MsoNormal"><b><span lang="EN-US"><font color="#000080">EJB</font></span><font color="#000080"><span style="font-family:
宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">服务器</span></font><span lang="EN-US"><font color="#000080"><o:p>
</font>
</o:p>
</span></b></p>
<p class="MsoNormal"><span lang="EN-US">EJB</span><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">服务器为</span><span lang="EN-US">enterprise
beans</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">和运行</span><span lang="EN-US">beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">的容器提供系统服务。它必须具有一个</span><span lang="EN-US">JIDI</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" style="mso-bidi-font-size:10.0pt;font-family:Verdana;color:black">Java
</span><span style="mso-bidi-font-size:10.0pt;font-family:宋体;mso-ascii-font-family:Verdana;
mso-hansi-font-family:Verdana;color:black">命名和目录接口</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">）访问能力的命名服务和事务管理。</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">服务器经常会提供额外的特征以区别于它的竞争者。</span><span lang="EN-US">Borland</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">公司的</span><span lang="EN-US">AppServer</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">就是一个</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">服务器的例子。</span></p>
<p class="MsoNormal"><b><span lang="EN-US"><font color="#000080">EJB</font></span><font color="#000080"><span style="font-family:
宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">容器</span></font></b></p>
<p class="MsoNormal"><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">一个容器是一个或多个</span><span lang="EN-US">enterprise
beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">的运行时系统。它提供了</span><span lang="EN-US">beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">和</span><span lang="EN-US">EJB</span><span style="font-family:
宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">服务器的通信。它提供了事务、安全和网络分布管理。一个容器既是代码又是一种为特殊的</span><span lang="EN-US">enterprise
bean</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">生成代码的工具。一个容器也提供了一个</span><span lang="EN-US">enterprise
bean</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">的部署工具，和一种监测和管理应用程序的方法。</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">服务器和</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">容器组合在一起为</span><span lang="EN-US">bean</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">提供了运行环境。容器为一个或多个</span><span lang="EN-US">beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">提供管理服务。虽然服务器为</span><span lang="EN-US">bean</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">提供了各种服务，但获取这些服务是由容器为</span><span lang="EN-US">beans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">做的。</span></p>
<p class="MsoNormal"><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">虽然容器是</span><span lang="EN-US">Enterprise
JavaBeans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">体系结构中的关键部分，但</span><span lang="EN-US">enterprise
bean</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">开发者和应用组合者不必关心它，在</span><span lang="EN-US">EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">分布式应用程序中它隐于幕后。因本书不再进一步解释容器及其工作方式。要得到更多的关于容器的资料，可以参考</span><span lang="EN-US">Enterprise
JavaBeans</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">规范</span><span lang="EN-US">1.1</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">。要得到更多的关于</span><span lang="EN-US">Borland
EJB</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">容器的资料，请参阅</span><i><span lang="EN-US">Borland
AppServer's Enterprise JavaBeans </span><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">开发指南</span><b><span lang="EN-US"><o:p>
</o:p>
</span></b></i></p>
<p class="MsoNormal"><b><font color="#000080"><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">一个</span><span lang="EN-US">Enterprise
JavaBeans</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">是如何运作的</span></font><span lang="EN-US"><o:p>
</o:p>
</span></b></p>
<p class="MsoNormal"><span lang="EN-US">bean</span><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">开发者必须创建以下这些接口和类：</span></p>
<p class="MsoNormal" style="margin-left:57.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo1;
tab-stops:list 57.0pt"><span lang="EN-US" style="font-family:
Wingdings">l<span style="font:7.0pt "Times New Roman"">
</span></span><span lang="EN-US">bean</span><span style="font-family:
宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">的本地接口（</span><span lang="EN-US">home
interface</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">）</span></p>
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