Java Practical info

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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b>The Element of struts
Architecture</b><o:p></o:p></span><br />
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%; mso-bidi-font-family: Georgia; mso-fareast-font-family: Georgia;">1.<span style="font-family: 'Times New Roman'; font-size: 7pt; line-height: normal;">       </span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">The
Action Servlet:  The Action Servlet of
struts framwwork is an implementation of front controller pattern and java
servlet component i.e is a servlet front for struts application. The
ActionServlet is a subtype of javax.servlet.http.HttpServlet and implements
init(), doGet(), doPost() and destroy() methods. The ActionServlet init()
method is responsible to find the user configured struts modules and locate the
struts configuration file of each module, then read, validate the configuration
and load the details into moduleconfig object which is further injected into
the module specific RequestProcessor instance.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">The
RequestProcessor further ses the ModuleConfig to get all the moule specific
details. Once if all these initializations are successfully done then the
ActionServlet instance is put into service, which provides an entry point to
serve the client requests using these configurations loaded. This means that
once if the ActionServlet is initialized any chages into the configuration
files are not affected until the ActionServlet is reinitialized which can be
done by redeploying the containing web application.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">The
ActionServlet accepts HTTP GET and POST method request where the doGet() and
doPost() method implementations of ActionServlet just call the protected
process() method of the same class where all the request handling logic is  implemented.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">The ActionServlet
process() method identifies the module that client has requested for , this is
done by matching the first part of the request URL with the configured modules.
There after it gets the RequestProcessor instance of the respecting module and
delegates the request to that RequestProcessor instance by invoking process()
method on the located RequestProcessor instance.<o:p></o:p></span></div>
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<span style="line-height: 18px; text-align: left;"><span style="font-family: Georgia, serif;"><b>Configuring</b></span></span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><b> <o:p></o:p></b></span><span style="line-height: 18px; text-align: left;"><span style="font-family: Georgia, serif;"><b>Action-Servlet</b></span></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">As we
have discussed in the above section that the ActionSerlvet class in the front
controller class that recives all incoming HTTP client requests for the
application. In addition, ActionSerlvet is responsible for initializing the
struts frame work for out application, and is a servlet extending HttpServlet
just like any other servlet and thus ActionSerlvet is also required to be
configured in out web application like any other servlet i.e inot Web
application deployment descriptor (web.xml). Since ActionServlet has to be
configured to receive all the requests to out application i.e for various
services. ActionSerlvet’s mapping should be generic and there are two
approaches to configure ActionServlet to recive all requests for our
application. First, Action Servlet can be configured using path mapping, as
shown in the following code snippet.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><web-app><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><!—ActionServlet
Declaration</span><span style="font-family: Wingdings; font-size: 12.0pt; line-height: 115%; mso-ascii-font-family: Georgia; mso-char-type: symbol; mso-hansi-font-family: Georgia; mso-symbol-font-family: Wingdings;">à</span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"> <Servlet><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <Servlet-name>action</servlet-name><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <servlet-class></span><b><span style="font-family: "Georgia","serif"; line-height: 115%; mso-bidi-font-size: 12.0pt;">org.apache.struts.action.ActionServlet</span></b><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"></servlet-class><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <init-param><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <param-name>config</param-name><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <param-value>/WEB-ING/Struts-config.xml</param-value><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <load-on-startup>1</load-on-startup><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><servlet><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><!---
Action Servlet Mapping><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><servlet-mapping><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"> 
<Servlet-name>action</servlet-name><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"> <url-pattern./do/*</url-pattern><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"></servlet-mapping><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"></web-app><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">In this
case all the request for this context whose servletPath starts with / do are
dispatched by the web container to the ActionServlet which further takes the
responsibility to handle the request as explained in the above section. As
shown in the above code it is not mandatory to confirure only /do/* instead we
are allowed to configure any other path mapping also.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">The
second approach to configure the mapping for ActionServlet is to use extension
mapping as shown in the below give code snippet.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><web-app><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><!—ActionServlet
Declaration</span><span style="font-family: Wingdings; font-size: 12.0pt; line-height: 115%; mso-ascii-font-family: Georgia; mso-char-type: symbol; mso-hansi-font-family: Georgia; mso-symbol-font-family: Wingdings;">à</span><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"> <Servlet><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <Servlet-name>action</servlet-name><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <servlet-class></span><b><span style="font-family: "Georgia","serif"; line-height: 115%; mso-bidi-font-size: 12.0pt;">org.apache.struts.action.ActionServlet</span></b><span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"></servlet-class><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <init-param><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <param-name>config</param-name><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <param-value>/WEB-ING/Struts-config.xml</param-value><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">            <load-on-startup>1</load-on-startup><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><servlet><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><!---
Action Servlet Mapping><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"><servlet-mapping><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"> 
<Servlet-name>action</servlet-name><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"> <url-pattern>*.do</url-pattern><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"></servlet-mapping><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;"></web-app><o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">In this
case all the request for this context whose servletPath ends with .do extension
are dispatched by the web container to the ActionServlet which further takes
the responsibility to handle the request as explained in the above section. As shown
in the above code its is not mandatory to configure only .do instead we are
allowed to configured any other textension also excluding the reserved
extension like jsp,jspx,sun,java etc.<o:p></o:p></span></div>
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<span style="font-family: "Georgia","serif"; font-size: 12.0pt; line-height: 115%;">NextPost
Struts configuration file and more component………………….<o:p></o:p></span></div>
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Struts Architecture

The Element of struts Architecture 1. The Action Servlet: The Action Servlet of struts framwwork is an implementation of ...