Construct org.springframework.core.convert.TypeDescriptor programatically for collections [SPR-7597]

[spring-projects-issues]

!!Use pwebb rather than philw opened SPR-7597 and commented

Although TypeDescriptor can determine collection element types from fields and methods as far as I can there is no way to do this programmatically. Could adding a TypeDescriptor.forCollection method be considered?

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Affects: 3.0.4

Attachments:

• org.springframework.core.patch (4.25 kB)

Issue Links:

• TypeDescriptor.forElementType() does not work for TypeDescriptor obtained via TypeDescriptor.valueOf() [SPR-7390] #12048 TypeDescriptor.forElementType() does not work for TypeDescriptor obtained via TypeDescriptor.valueOf()

[spring-projects-issues]

!!Use pwebb rather than philw commented

Patch

[spring-projects-issues]

Keith Donald commented

Phil,
Can you see if the existing TypeDescriptor#forObject(Object) meets your needs?

[spring-projects-issues]

!!Use pwebb rather than philw commented

Keith,

The problem with forObject is that it can only deduce the generic collection type if there is an element in the collection, same with valueOf. If you build the TypeDescription from a field or methodParameter then the generic type can be deduced but what I really want to do is build a TypeDescriptor programatically when I know the element type that should be in the collection. This would be particularly useful when writing test cases for converters that deal with collections.

Another idea that had for this (and this might be a bit crazy) is to use the converter service to populate Lists based on the generic type of the list. So for example I convert from MyEnum.class to List<MyEnum> by having a converter that calls MyEnum.values().

This code probably explains better than my ramblings:

https://github.com/philwebb/springfaces/blob/master/springfaces/src/main/java/org/springframework/springfaces/converter/ClassToEnumsConverter.java

https://github.com/philwebb/springfaces/blob/master/springfaces/src/test/java/org/springframework/springfaces/converter/ClassToEnumsConverterTest.java

Phil.

[spring-projects-issues]

Keith Donald commented

Added TypeDescriptor.collection and TypeDescriptor.map