@JsonUnwrapped completeness: allow more flexible renaming

[jhhdk]

Prefix and Suffix not sufficient for every use case. While a very narrow use case consider following example:

class Rectangle {
   @JsonUnwrapped(prefix="topLeft")
   Point topLeft;

   @JsonUnwrapped(prefix="bottomRight")
   Point bottomRight;
}

For now this would be serialized as: { topLeft.x: 0, topLeft.y: 0, bottomRight.x: 2048. bottomRight.y: 1080 }

From documentation it would seem its not possible to coerce Jackson into serializing it as: { left: 0, top: 0, right: 2048 bottom: 1080, }

I am not entirely sure that this is even possible but I suppose something along the lines of:

class Rectangle {
   @JsonUnwrapped(
       names = {"x","y"},
       renames= {"left", "top"}
   )
   Point topLeft;

   @JsonUnwrapped(
       names = {"x","y"},
       renames= {"right", "bottom"}
   )
   Point bottomRight;
}

Would cover all thinkable use cases.

[cowtowncoder]

Underlying mechanism does not rely on existing strategies, so technically it should be possible to extend it. As an alternative to two properties, it'd also be possible to define a helper type to do something like

names = { @Rename(from="x", to="left"), @Rename(from="y", to="top")

but I guess that is a matter of preference. (basic java.util.Map can not be used as annotation value, alas).

One potential problem exists however; use of nested @JsonUnwrapped might not work as expected, or might require use of fully expanded names. With prefix/suffix it is easy enough to simply prepend/append; with mapping, matching would probably require care for such cases.

[zartc]

A nice way to provide this functionnality to Jackson users would be to use the same mecanism used by Hibernate with the @AttributeOverride annotation to rename properties of contained object at the point of inclusion.

That would give:

class Rectangle {
   @JsonUnwrapped
   @JsonAttributeOverride(name = "x", out="left")
   @JsonAttributeOverride(name = "y", out="top")
   Point topLeft;

   @JsonUnwrapped
   @JsonAttributeOverride(name = "x", out="right")
   @JsonAttributeOverride(name = "y", out="bottom")
   Point bottomRight;
}

It would have to work also with non-unwrapped objects so that two different container objects containing the same kind of object can decide what name to give to properties of the contained object independantly.

Hope this help.