Initialization parameters for Web. xml

Initialization parameters for Web. xml

　　

--------- first declares that this is the initialization configuration of the Context-param,init-param parameter in the Web ----------

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First, the initialization of parameters

　　There are two types of parameters that can be defined in Web. xml:

　(1) Parameters within the application range, stored in the ServletContext, are configured in Web. Xml as follows:　　　

< Context-param >          <param-name>context/param</param-name>           <param-value>avalible during application</ param-value></context-param>

(2) The parameters within the Servlet range can only be obtained in the servlet's init () method, which is configured in Web. Xml as follows:

<servlet>    <Servlet-name>Mainservlet</Servlet-name>    <Servlet-class>Cn.jbit.controller.MainServlet</Servlet-class>   <init-param> <param-name>param1</param-name> <param-value>avalible in Servlets in It () </param-value> </init-param>    <Load-on-startup>0</Load-on-startup></servlet>

In a servlet, you can use the code separately:

 PackageCn.jbit.controller;Importjavax.servlet.ServletException;ImportJavax.servlet.http.HttpServlet; Public classMainservletextendsHttpServlet { PublicMainservlet () {Super(); }     Public voidInit ()throwsservletexception {System.out.println ("The following parameters are stored in the ServletContext"); System.out.println (getservletcontext (). Getinitparameter("Context/param")); System.out.println ("The following two parameters param1 are stored in the servlet"); System.out.println ( This.Getinitparameter("param1")); }}

The first parameter in the servlet can be obtained by Getservletcontext (). Getinitparameter ("Context/param")
The second parameter can only be obtained by This.getinitparameter ("param1") in the servlet's init () method

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Second, the initialization parameters have been

 <!--application Mode --
<Context-param>  <Param-name>Count</Param-name>  <Param-value>1200</Param-value></Context-param>  
<!--servlet-->
<servlet>    <Description>Loginservlet</Description>    <Display-name>Loginservlet</Display-name>    <Servlet-name>Loginservlet</Servlet-name>    <Servlet-class>Loginservlet</Servlet-class>   
 　　 <!--servlet init at initialization ()--
<Init-param>      <Description>Number of system initializations</Description>      <Param-name>Num</Param-name>      <Param-value>100</Param-value>    </Init-param>
  </servlet>

  <servlet-mapping>    <Servlet-name>Loginservlet</Servlet-name>    <Url-pattern>/loginservlet</Url-pattern>  </servlet-mapping>

Methods and similarities and differences in obtaining parameters in a servlet:

  
 response.setcharacterencoding ("GB2312"); System.out.println ("Getservletcontext ():" +Getservletcontext ()); ServletContext Context=getservletconfig (). Getservletcontext (); String num =context.getinitparameter ("num");//<init-param> Get No value  String Count=context.getinitparameter ("Count");//<context-param> get to ValueSYSTEM.OUT.PRINTLN ("num:" +num);//NULLSystem.out.println ("Count:" +count);// -System.out.println ("num:" +getservletconfig (). Getinitparameter ("num"));//100 Gets the value System.out.println ("Count:" +getservletconfig (). Getinitparameter ("Count"));//null Get no value

Initialization parameters for Web. xml