ActionServlet workflow

最新推荐文章于 2020-05-08 16:07:11 发布

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最新推荐文章于 2020-05-08 16:07:11 发布

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分类专栏： struts框架文章标签： workflow action path processing service class

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本文详细介绍了Apache Struts框架的核心组件ActionServlet的工作流程。当接收到客户端请求时，ActionServlet通过struts-config.xml配置文件确定对应的Action，并创建或获取ActionForm实例来填充请求参数。之后验证ActionForm的有效性，调用Action进行业务处理并返回结果。

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The org.apache.struts.action.ActionServlet is the backbone of all Struts applications. It is the mainController component that handles client requests and determines which org.apache.struts.action.Action
will process each received request. It serves as an Action factory—creating specific Action classes based on the user's request.

When the ActionServlet receives a request, it completes the following steps:
1. The doPost() or doGet() methods receive a request and invoke the process() method.
The process() method gets the current RequestProcessor and invokes the RequestProcessor.process() method.

2.The process() method gets the current RequestProcessor and invokes the RequestProcessor.process() method.

3.The RequestProcessor.process() method is where the current request is actually serviced. This
method retrieves, from the struts-config.xml file, the <action> element that matches the path
submitted on the request. It does this by matching the path passed in the <html:form /> tag's action
element to the <action> element with the same path value. Here's an example of this match:
<html:form action="/Lookup" name="lookupForm" type="app.LookupForm" >

4.When the RequestProcessor.process() method has a matching <action>, it looks for a <form-bean>
entry that has a name attribute that matches the <action> element's name attribute. The following
code snippet contains a sample match:
<form-beans>
                      <form-bean name="lookupForm" type="app.LookupForm"/>
</form-beans>
<action path="/Lookup" type="app.LookupAction" name="lookupForm" >
            <forward name="success" path="/quote.jsp"/>
            <forward name="failure" path="/index.jsp"/>
</action>

5.When the RequestProcessor.process() method knows the fully qualified name of the FormBean, it
creates or retrieves a pooled instance of the ActionForm named by the <form-bean> element's type
attribute and populates its data members with the values submitted on the request.

6.After the ActionForm's data members are populated, the RequestProcessor.process() method calls
the ActionForm.validate() method, which checks the validity of the submitted values.

7.At this point, the RequestProcessor.process() method knows all that it needs to know and it is time
to actually service the request. It does this by retrieving the fully qualified name of the Action class
from the <action> element's type attribute, creating or retrieving the named class, and calling the Action.execute() method.

8.When the Action class returns from its processing, its execute() method returns an ActionForward object that is used to determine the target of this transaction. The RequestProcessor.process()
method resumes control, and the request is then forwarded to the determined target.

9.At this point, the ActionServlet instance has completed its processing for this request and is ready
to service future requests.