Difference between portlets and gadgets

In the portlets world, you do everything server-side (on the server where the data is held). In the gadgets world, the UI is rendered entirely using HTML , XML and JavaScript. 

1) Gadget is written using JS, HTML, XML
    Portlet Java + JS, HTML, XML

2) Gadget - runs on the browser
    Portlet - runs on the Portal server to produce HTML

3) Gadget - Malfunction would only effect the client using it
    Portlet - Can bring down the whole server

4) Gadget - yet another way of writing portal page
    JSR Portlet - Traditional Java based (JSR driven) approach to writing portal pages


Here is a presentation which will give more details about portlets and gadgets

Shindig Apachecon Asia 09

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