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Man Pages


Manual Reference Pages  -  SERVLET::SERVLET (3)

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NAME

Servlet::Servlet - servlet interface

CONTENTS

SYNOPSIS



  $servlet->getServletInfo();

  $servlet->init($config);

  # later

  $servlet->service($request, $response);

  my $config = $servlet->getServletConfig();

  # finally

  $servlet->destroy();



DESCRIPTION

A servlet is a Perl component that runs within a servlet container. Servlets receive and respond to requests from Web clients, usually across HTTP.

To implement this interface, you can write a generic servlet that extends <B>Servlet::GenericServletB> or an HTTP servlet that extends <B>Servlet::Http::HttpServletB>.

This interface deinfes methods to initialize a servlet, to service requests, and to remove a servlet from the server. These are known as life-cycle methods and are called in the following sequence:
1. The servlet is constructed, then initialized with init().
2. Any calls from clients to service() are handled.
3. The servlet is taken out of service, then destroyed with destroy().
In addition to the life-cycle methods, this interface provides the getServletConfig method, which the servlet can use to get any startup information, and getServletInfo(), which allows the servlet to return basic information about itself, such as author, version and copyright.

METHODS

destroy() Called by the servlet container to indicate to a servlet that the servlet is being taken out of service. This method is only called once all threads within the servlet’s service() method have exited or after a timeout period has passed. After the servlet container calls this method, it will not call service() again on this servlet.

This method gives the servlet an opportunity to clean up any resources that are being held (for example, memory, file handles, threads) and make sure that any persistent state is synchronized with the servlet’s current state in memory.

getServletConfig() Returns a <B>Servlet::ServletConfigB> object which contains initialization and startup parameters for this servlet. The object returned is the one passed to the init() method.

Implementations of this interface are responsible for storing the object so that this method can return it. The <B>Servlet::GenericServletB> class, which implements this interface, already does this.

getServletInfo() Returns information about the servlet, such as author, version, and copyright.

The string that this method returns should be plain text and not markup of any kind (such as HTML, XML etc).

init($config) Called by the servlet container to indicate to a servlet that the servlet is being placed into service.

The servlet container calls the init() method exactly once after instantiating the servlet. The init() method must complete successfully before the servlet can receive any requests.

The servlet container cannot place the servlet into service if init().
1. Throws a <B>Servlet::ServletExceptionB>
2. Does not return within a time defined by the servlet container

<B>Parameters:B>
$config a <B>Servlet::ServletConfigB> object containing the servlet’s configuration and initialization parameters

<B>Throws:B>
<B>Servlet::ServletExceptionB> if an exception has occurred that interferes with the servlet’s normal operation

service($request, $response) Called by the servlet container to allow the servlet to respond to a request.

This method is only called after the servlet’s init() method has completed successfully.

Servlets may run inside multithreaded servlet containers that can handle multiple requests concurrently. Developers must be aware to synchronize ac cess to any shared resources such as files, network connections, and as well the servlet’s class and instance variables.

<B>Parameters:B>
$request the <B>Servlet::ServletRequestB> object that contains the client’s request
$response the <B>Servlet::ServletResponseB> object that contains the servlet’s response

<B>Throws:B>
<B>Servlet::ServletExceptionB> if an exception occurs that interferes with the servlet’s normal operation

SEE ALSO

Servlet::GenericServlet, Servlet::ServletConfig, Servlet::ServletException, Servlet::ServletRequest, Servlet::ServletResponse

AUTHOR

Brian Moseley, bcm@maz.org
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perl v5.20.3 SERVLET::SERVLET (3) 2001-07-13

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