BeanEditor should provide a "BeanEditContext" into the environment. (or
PropertyEditContext should include the bean class).
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Key: TAPESTRY-2592
URL: https://issues.apache.org/jira/browse/TAPESTRY-2592
Project: Tapestry
Issue Type: Improvement
Components: quickstart
Affects Versions: 5.0.14
Environment: any
Reporter: Robert Zeigler
PropertyEditor has the useful feature of providing the PropertyEditContext to
the environment. In this manner, custom blocks can be used to edit the current
property and have the ability to "get" and "set" the property of the bean,
display labels based on the property id, and so forth.
It can be useful, however, to have at runtime the knowledge of which bean type
is being edited, or even have access to the bean under edit.
I propose a new "BeanEditContext" environment variable. The BeanEditor would
push this object onto the environment. The BeanEditContext would contain, at a
minimum, a "getBeanClass" method which would return the class of the current
bean being edited.
An alternative solution would be to add a "getBeanClass" method to the
PropertyEditContext.
Use case and discussion:
I'm currently working on a tapestry-cayenne integration module. One thing that
would be nice is for the module to add all of the validation constraints for a
particular property that are known to cayenne. The ideal way to handle this
would be to contribute a ValidationConstraintGenerator. However, the
generator's method is passed only the type of property being edited, and the
annotations that were on that property. Cayenne does not require that
validation constraints be specified via annotations. Hence, the integration
module cannot rely on the presence of annotations to determine the validation
constraints for a property type. Nor is the type of property sufficient, as it
is impossible to distinguish between the validations for two different "String"
by the class "String" alone. At the time of constraint generation, the
PropertyEditContext is available from the environment, which helps the
situation by providing the Property's name. However, the PropertyEditContext
does not provide information about the bean class being edited. In order to
lookup the wealth of information available from Cayenne for, eg, generating
validators, I need to have this information available. As stated, this could
be achieved by a BeanEditContext, or by adding "getBeanClass" to PropertyEditor.
The main issue with using a BeanEditContext is that code which relies on that
environment object being available could be called without the BeanEditor
having a chance to setup the context, since PropertyEditor can be used outside
of BeanEditor. In practice, the PropertyEditor is rarely used outside the
context of BeanEditor.
The advantage is that it is a separation of concerns: PropertyEditor doesn't
care about the bean being edited. It would require no changes to the existing
PropertyEditor/validator/etc. API.
Unless I receive direction otherwise, I'll be contributing a patch for this
feature which implements it as a BeanEditContext environment variable.
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