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From Ken Ramirez <krami...@thejavathinktank.org>
Subject Re: Portlet & servlet.
Date Sat, 22 Jan 2005 21:12:06 GMT
>
>
>lureveru@tin.it wrote:
>What are differences between portlet and servlet ?
>  
>
Essentially, Servlets provide content that normally takes up the whole 
page in a browser (unless you're using frames), and portlets provide 
content that is wrapped by a window. With portlets, you can have 
multiple portlets side by side with one another and each one can provide 
content and functionality that is different from the other. A portlet 
can provide the complete interaction for one type of application, while 
another portlet can provide content for another type of application. The 
portal can provide some house keeping functionality and secured single 
point of entries to all of the portlets on a page. As for the 
particulars (similarities/differences) between them, please continue 
reading.

Here are some similarities:

    * Servlets and portlets are web based components that utilize Java
      for their implementation
    * Portlets are managed by a portlet container similar to a servlet
      container
    * Both of these components generate content, which can be static or
      dynamic
    * Both portlets and servlets have a lifecycle that is controlled by
      the container
    * The client/server model is used for both servlets and portlets
    * The packaging and deployment are essentially the same
    * The manner in which the classes are loaded and the class loaders
      that perform the work are also the same
    * Lifecycle management is similar
    * The Request and Response semantics are also similar

Here are some differences:

    * Servlets can provide complete web pages, whereas portlets only
      provide fragments. These fragments are then aggregated to form a
      complete web page by the portal
    * Portlets aren’t allowed to generated HTML code that contains tags
      such as base, body, frame, frameset, head, html, or title. The
      iframe tag can be used with caution.
    * The user cannot access a portlet directly using a URL in the way
      that a servlet is accessed. Instead, the URL points to the page
      containing all of the portlets on one page
    * Communication between the web client and the portlets is performed
      through the portal
    * Portlets can be provided with buttons or controls to manipulate
      the portlets’ window states or portlet modes
    * Multiple instances of a single portlet can be placed onto the same
      page
    * Portlets support persistent configuration and customization
    * Portlets also support user profile information
    * Portlets support two scopes within the session; application scope
      and portlet scope

There are several things that servlets are allowed to do, but portlets 
aren’t. These include the following:

    * Portlet aren’t allowed to set the character set encoding of the
      response
    * Portlet also aren’t allowed to set the HTTP headers on the response
    * Portlet cannot manipulate the URL of the client request to the portal

Hope that helps :-)

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Ken Ramirez
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Check out my Blog at: http://weblogs.java.net/blog/ken_ramirez
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