Three major examples of Servlet method implementation

The Servlet method is first developed by implementing the servlet interface.

 

  
/***//**
  
* @ (#) Hello. java
  
*
  
*
  
* @ Author shiyi05
  
* @ Version 1.00 2008/5/9
  
*/
  
// This is my first servlet. It is developed using the implements Servlet to implement the servlet interface.
  
Package com. rao;
  
Import javax. servlet .*;
  
Import javax. servlet. ServletConfig;
  
Import javax. servlet. ServletException;
  
Import javax. servlet. ServletRequest;
  
Import javax. servlet. ServletResponse;
  
Import java. io. IOException;
  
Import javax. servlet .*;
  
Import java. io .*;
  
 
  
 
  
 
  
Public class Hello implements Servlet
  
...{
  
 
  
Public Hello ()
  
...{
  
}
  

  

  
/***//**
  
* Method init
  
*
  
*
  
* @ Param parm1
  
*
  
@ Throws ServletException
  
*
  
*/
  
// This function is used to initialize the servlet. This function will only be called once when the user accesses the servlet for the first time)
  
Public void init (ServletConfig parm1) throws ServletException
  
...{
  
// TODO: Add your code here
  
System. out. println ("init ");
  
}
  
 
  
/***//**
  
* Method getServletConfig
  
*
  
*
  
* @ Return
  
*
  
*/
  
Public ServletConfig getServletConfig ()
  
...{
  
// TODO: Add your code here
  

  
Return null;
  
}
  
 
  
/***//**
  
* Method service
  
*
  
*
  
* @ Param req is used to obtain client information.
  
* @ Param res is used to return information to the client.
  
*
  
@ Throws ServletException
  
@ Throws IOException
  
*
  
*/
  
// This function is used to process the business logic. Each time a user accesses the servlet, it is called
  
Public void service (ServletRequest req, ServletResponse res) throws ServletException, IOException
  
...{
  
// TODO: Add your code here
  
System. out. println ("service ");
  
PrintWriterPw=Res. GetWriter ();
  
Pw. println ("Hello world! ");
  
}
  
 
  
/***//**
  
* Method getServletInfo
  
*
  
*
  
* @ Return
  
*
  
*/
  
Public String getServletInfo ()
  
...{
  
// TODO: Add your code here
  
Return "";
  
}
  
 
  
/***//**
  
* Method destroy
  
*
  
*
  
*/
  
Public void destroy ()
  
...{
  
// TODO: Add your code here
  
System. out. println ("destroy ");
  
}
  

  
}
 

Implement the second Servlet method by inheriting GenericServlet Development

 

  
/***//**
  
* @ (#) HelloGen. java
  
*
  
*
  
* @ Author shiyi05
  
* @ Version 1.00 2008/5/9
  
*/
  
 
  
 
  
// This is the second way to develop servlet. It is developed by inheriting GenericServlet
  
Package com. rao;
  
Import javax. servlet. GenericServlet;
  
Import java. io .*;
  
Import javax. servlet .*;
  
 
  
 
  
Public class HelloGen extends GenericServlet
  
...{
  
 
  
Public HelloGen ()
  
...{
  
}
  

  
// Rewrite the service () method
  
Public void service (ServletRequest req, ServletResponse res)
  
...{
  
Try
  
...{
  
PrintWriterPw=Res. GetWriter ();
  
Pw. println ("Hello World, Generic ");
  
}
  
Catch (Exception ex)
  
...{
  
Ex. printStackTrace ();
  
}
  

  

  
}
  

  

  
}
 

The third and most common Servlet method is implemented by inheriting the HttpServlet class.

 

  
/**
  
* @ (#) HelloHttp. java
  
* @ Author shiyi05
  
* @ Version 1.00 2008/5/9
  
*/
  
// This is the third servlet development method, which is implemented by inheriting the HttpServlet class.
  
Package com. rao;
  
Import javax. servlet. http .*;
  
Import java. io .*;
  
Public class HelloHttp extends HttpServlet
  
...{
  
 
  
Public HelloHttp ()
  
...{
  
}
  

  
// Process Get requests
  
Public void doGet (HttpServletRequest req, HttpServletResponse res)
  
...{
  
Try
  
...{
  
PrintWriterPw=Res. GetWriter ();
  
Pw. println ("Hello World, HttpServlet ");
  
}
  
Catch (Exception ex)
  
...{
  
Ex. printStackTrace ();
  
}
  

  
}
  

  
Public void doPost (HttpServletRequest req, HttpServletResponse res)
  
...{
  
This. doGet (req, res );
  

  
}
  
}
 

Finally, deploy the three servlets in the web. xml file.

 

  
<? XmlVersion="1.0" Encoding=ISO-8859-1"? >
  
 
  
<Web-appXmlns=Http://java.sun.com/xml/ns/javaee" 
  
Xmlns: xsi=Http://www.w3.org/2001/XMLSchema-instance" 
  
Xsi: schemaLocation=Http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
  
Version="2.5">
  
 
  
<Display-name> Welcome to Tomcat </display-name>
  
<Description>
  
Welcome to Tomcat
  
</Description>
  

  
<Servlet>
  
<! -- Servlet name, which is arbitrary -->
  
<Servlet-name> Hello </servlet-name>
  
<! -- Specify the servlet Path, package name + class name -->
  
<Servlet-class> com. rao. Hello </servlet-class>
  
</Servlet>
  
<Servlet-mapping>
  
<! -- Same as above -->
  
<Servlet-name> Hello </servlet-name>
  
<! -- The URL used to access the servlet in the browser is arbitrary -->
  
<Url-pattern>/Hello </url-pattern>
  
</Servlet-mapping>
  

  

  
<Servlet>
  
<! -- Servlet name, which is arbitrary -->
  
<Servlet-name> HelloGen </servlet-name>
  
<! -- Specify the servlet Path, package name + class name -->
  
<Servlet-class> com. rao. HelloGen </servlet-class>
  
</Servlet>
  
<Servlet-mapping>
  
<! -- Same as above -->
  
<Servlet-name> HelloGen </servlet-name>
  
<! -- The URL used to access the servlet in the browser is arbitrary -->
  
<Url-pattern>/HelloGen </url-pattern>
  
</Servlet-mapping>
  

  
<Servlet>
  
<! -- Servlet name, which is arbitrary -->
  
<Servlet-name> HelloHttp </servlet-name>
  
<! -- Specify the servlet Path, package name + class name -->
  
<Servlet-class> com. rao. HelloHttp </servlet-class>
  
</Servlet>
  
<Servlet-mapping>
  
<! -- Same as above -->
  
<Servlet-name> HelloHttp </servlet-name>
  
<! -- The URL used to access the servlet in the browser is arbitrary -->
  
<Url-pattern>/HelloHttp </url-pattern>
  
</Servlet-mapping>
  
 
  
</Web-app>
 

The Servlet method is developed in three ways !! I hope this will help you implement the Servlet method.

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