Ben Weidig created TAP5-2763:
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Summary: @RequestParameter improved blank handling
Key: TAP5-2763
URL: https://issues.apache.org/jira/browse/TAP5-2763
Project: Tapestry 5
Issue Type: Improvement
Components: tapestry-core
Affects Versions: 5.8.3
Reporter: Ben Weidig
As ValueEncoders are used to convert a parameter value to its actual type, only
Boolean and Number-based types result directly in {{null}} for a blank value.
All other types use their TypeCoercer-based ValueEncoder, which not necessarily
work.
However, I believe that if {{allowBlank = true}} is set, then a blank parameter
should be able to lead to a {{null}} value.
Three possible changes come to mind to support blank --> null:
* Always treat blank as {{null}} before passing it the ValueEncoder
* Add {{boolean treatBlankAsNull() default false;}} to {{@RequestParameter,
or}}
* {{adding String blankValue() String default ""; to @RequestParameter that is
used instead of the parameter value if blank}}
Personally, I'd prefer the first option.
The {{TypeCoercedValueEncoderFactory}} would handle
{{{}Boolean{}}}/{{{}Number{}}} just like before, but @RequestParamter wouldn't
crash anymore if no valid coercion is possible for an empty String.
My proof-of-concept works and I might provide a feature branch soon.
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