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<p class="MsoNormal" style="text-indent:21.0pt"><span style="font-family:宋体;
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"">应用程序的工作被分割为六个分工明确的角色。每一个角色都是各领域的专家。通过这样的分割方式，创建和管理一个分布式系统变得更为容易。</span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><font color="#000080"><b><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">应用角色</span><span lang="EN-US">(Application
roles)</span></b></font></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">应用角色负责为</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"">编写代码和开发应用程序使用它们。虽然标准不同，但这两个角色都需要懂得怎样使商业逻辑运行起来。以下就是着两个应用角色：</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 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（</span><span lang="EN-US">Bean
provider</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 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"">开发者创建</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"">并编写</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"">中的商业逻辑规则。他们也负责定义</span><span lang="EN-US"><span style="mso-tab-count:1">
</span>beans</span><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">的</span><span lang="EN-US">remote</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">home</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">接口，创建</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"">部署描述器（</span><span lang="EN-US">deployment
descriptors</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">. Bean </span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"">开发者并不需要知道怎样组合与部署他们的</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"">。</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"">应用组合者（</span><span lang="EN-US">Application
assembler</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"">应用组合者编写使用</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"">的应用程序。这些应用程序通常包含其它的组件，列如</span><span lang="EN-US">GUI
clients,applet,JSP</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">servlets</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">。这些组件被组合入分布式应用程序。应用组合者要将组合说明添加入</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"">部署描述器（</span><span lang="EN-US">deployment
descriptors</span><span style="font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"">）。虽然应用组合者必须熟悉</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"">中包含的方法以用于调用它们，但他们不必知道这些方法是怎样实现的。</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">对</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"">感兴趣的</span><span lang="EN-US">Jbuilder</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">用户通常是</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"">开发者和应用组合者。因而主要是为他们编写的。</span><span lang="EN-US">Jbuilder</span><span style="font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"">具有向导、设计和其他工具，使用它们可以简化</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"">和应用程序的开发。</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><b><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman""><font color="#000080">底层结构角色</font></span><span lang="EN-US"><o:p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">没有底层结构的支持，</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"">和使用它们的应用程序不能运行。虽然两个底层结构角色差别很大，但它们总是由同一个开发商提供。它们结合在一起为</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"">提供系统级的服务运行环境。以下就是这两个底层结构角色：</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 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"">服务器提供者（</span><span lang="EN-US">EJB
server provider</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 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"">服务器提供者是负责分布式事务管理，分布式对象管理及其它系统级服务的专家。他们提供运行</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"">容器的应用框架。</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"">服务器提供者必须至少为</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"">提供一个命名服务和事务服务。</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 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"">容器提供者</span><span lang="EN-US">(EJB
Container Provider)</span></p>
<p class="MsoNormal" style="margin-left:57.0pt"><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"">容器提供者提供必须的部署工具来部署</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"">并为处于运行状态的</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"">提供支持。一个容器可以为一个或多个</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，它们代替</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"">与</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"">服务器通信，以访问</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"">需要的服务。</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">当前几乎所有实例中，</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"">服务器提供者和</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"">容器提供者来自同一个开发商。例如，</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"">既提供了服务器又提供了容器。</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><b><font color="#000080"><span style="font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"">部署与运行角色</span></font><span lang="EN-US"><font color="#000080"><o:p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-family:宋体;
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