I have come up with a library for doing haskell like lens operations on a
JsonNode. My need was from wanting to do complex edits on the JsonNode in a
fluent way. Currently they only way (I've found) to edit a tree is to do a
lot of casts with intermediate variables. With the JsonLens wrapper the
edits almost look like you are working directly with JsonNode tree but with
edit support. Here is an example of what it would look like.
Given the input:
{
"name": "Homer Simpson",
"address": {
"street": "742 Evergreen Ter.",
"city": "Springfield"
}
}
With the JsonLens adding a state would look like
JsonNode output = new JsonLens(input).path("address").set("state",
"Ohio").result();
this would return (there are options to edit in-place or do an non-mutating
copy on write). The main thing I want you to notice is that returned value
is not the address object but the whole tree with the address changed.
{
"name": "Homer Simpson",
"address": {
"street": "742 Evergreen Ter.",
"city": "Springfield",
"state": "Ohio"
}
}
This just barely scratches the surface. I'll paste a full method list at
the end.
My question to the list are:
1) Would anyone else like to use this?
2) If #1 is yes. What are best practices for packaging this up to be
compatible with jackson?
The only dependency is on the JsonNodeFactory and JsonNode classes.
Appendix: Full API
class JsonLens {
class Options {
JsonNodeFactory factory // the class used for generating empty
ObjectNode and ArrayNode as needed.
boolean immutable // copy on write
boolean throwClassCast // if the user steps out of bounds throw a
ClassCastException otherwise just make JsonNodes to make whatever they
write work.
}
JsonLens()
JsonLens(JsonNode)
JsonLens(JsonNode, Options)
JsonLens(Options)
JsonNode result() // when done with the edits this returns the result.
JsonLens append(boolean)
JsonLens append(byte)
JsonLens append(double)
JsonLens append(float)
JsonLens append(Function<JsonLens, JsonLens>) // function input is
always a lens to a MissingNode.
JsonLens append(int)
JsonLens append(JsonLens)
JsonLens append(JsonNode)
JsonLens append(long)
JsonLens append(short)
JsonLens append(String)
JsonLens appendAll(JsonLens) // recursive object and array merge
JsonLens appendAll(JsonNode) // recursive object and array merge
JsonLens insert(int, boolean)
JsonLens insert(int, byte)
JsonLens insert(int, double)
JsonLens insert(int, float)
JsonLens insert(int, Function<JsonLens, JsonLens>) // the methods that
take a function let the user do multiple edits all at once.
JsonLens insert(int, int)
JsonLens insert(int, JsonLens)
JsonLens insert(int, JsonNode)
JsonLens insert(int, long)
JsonLens insert(int, short)
JsonLens insert(int, String)
JsonLens path(int)
JsonLens path(String)
JsonLens remove(int)
JsonLens remove(String)
JsonLens set(boolean)
JsonLens set(double)
JsonLens set(Function<JsonLens, JsonLens>)
JsonLens set(int)
JsonLens set(int, boolean)
JsonLens set(int, double)
JsonLens set(int, Function<JsonLens, JsonLens>)
JsonLens set(int, int)
JsonLens set(int, JsonLens)
JsonLens set(int, JsonNode)
JsonLens set(int, String)
JsonLens set(JsonLens)
JsonLens set(JsonNode)
JsonLens set(long)
JsonLens set(String)
JsonLens set(String, boolean)
JsonLens set(String, double)
JsonLens set(String, Function<JsonLens, JsonLens>)
JsonLens set(String, int)
JsonLens set(String, JsonLens)
JsonLens set(String, JsonNode)
JsonLens set(String, long)
JsonLens set(String, String)
}
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