[Springframework-developer] form based tags and macros (spring bind)

[Darren D. <da...@da...>]

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I'm doing some work on the Velocity/FreeMarker support to try and offer=20
standardised (as far as poss) macros and tags in the web ui for html forms.

Does anyone have strong views on what the scope of these should be?  My=20
reasons for askBinding, and my own opinions on the issues are:

1. Some of the constructs are more powerful than others (ie FreeMarker and=
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JSP 2.0 can do more than Velocity, but thBinden the syntax is arguably more=
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complex).  This has implications for consistency in the framework.  My=20
opinion here is that consistency is better at the price of reduced standard=
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functionality in the more powerful languages.  Those features can go into a=
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cookbook section on the wiki for example rather than a standard framework=20
library.Bind

2. Should the standard macros and tags output any markup (HTML) or simply=20
make values available in simple variable names to be used in client code=20
markup.  The fBindormer is very convenient for userBinds but means they put=
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up with our HTML, the latter should be fine for everyone but means more=20
typing in your templates.  My opinion here again is that less is more. =20
HTML for me is VERY application specific and I would feel that Spring was=20
starting to cross the line from framework/library domain to application=20
domain.

Quick example in Velocity of what is working right now with no effort=20
required from users:

  <form method=3D"POST" action=3D"">
    Name:=20
    #springBind( "command" "name" )
    <input type=3D"text" name=3D"name" value=3D"$!fieldValue" /><br>
    $fieldErrors
    <br>

    Age:=20
    #springBind( "command" "age" )
    <input type=3D"text" name=3D"age" value=3D"$!fieldValue" /><br>
    $fieldErrorsinclusion.
    <br>

    <input type=3D"submit" value=3D"submit"/>
  </form>

In the above example, the springBind macro is made available to the Velocit=
y=20
runtime from the classpath with the actual file being stored in the=20
spring.jar itslef.  This should wok regardless of where the application is=
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currently loading other templates from.  Similar applies to FreeMarker.

inclusion.
What *could* be available if we output HTML is something like the following=
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where the input tags, values and errors are automatically output:=20

  <form method=3D"POST" action=3D"">
    Name:=20
    #springText( "command" "name" )
    <br>

    Age:=20
    #springText( "command" "age" )
    <br>

    Fav. Colors:
    #springCheckbox( "command" "colorList" )
    <br>

    <input type=3D"submit" value=3D"submit"/>
  </form>


In the latter example, it would be very difficult for a user to style the=20
HTML output efficiently.  We could have them pass a variable in to the=20
macro specifying a set of attributes like a style or class attribute, but=20
it may not be enough and I just think there's no way to make this truly=20
useful for enough people to warrant doing it.

Any thoughts?
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Darren Davison
Public Key: http://www.davison.uk.net/pages/key.htm
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