apoc.convert.fromJsonMap
Function APOC Core
apoc.convert.fromJsonMap('{"a":42,"b":"foo","c":[1,2,3]}'[,'json-path', 'path-options'])
Signature
apoc.convert.fromJsonMap(map :: STRING?, path = :: STRING?, pathOptions = null :: LIST? OF STRING?) :: (MAP?)
Usage Examples
The following converts a JSON map into a Cypher map:
RETURN apoc.convert.fromJsonMap('{"name": "Graph Data Science Library"}') AS output;
Output |
---|
{name: "Graph Data Science Library"} |
We can also use JSON path expressions to extract part of a JSON map.
For example, the following extracts the product
property from a JSON map and returns a map:
RETURN apoc.convert.fromJsonMap('{"product": {"name": "Bloom"}}', '$.product') AS output;
Output |
---|
{name: "Bloom"} |
If we try to convert a non-map structure, we’ll get an exception. For example:
RETURN apoc.convert.fromJsonMap('[{"name": "Neo4j"}]') AS output;
Failed to invoke function |
In this case we should instead use apoc.convert.fromJsonList.
Moreover, we can customize the Json path options, adding as third parameter (pathOptions
) a list of strings,
where the strings are based on Enum<Option>.
The default value is ["SUPPRESS_EXCEPTIONS", "DEFAULT_PATH_LEAF_TO_NULL"]
. Note that we can also insert []
, that is "without options".
So we can execute (with default pathOptions):
RETURN apoc.convert.fromJsonMap('{ "columns": {
"col2": {
"_id": "772col2"
}
}
}', '$.columns.col2') AS output;
output |
---|
{ "_id": "772col2" } |
or, with custom path options:
RETURN apoc.convert.fromJsonMap('{ "columns": {
"col2": {
"_id": "772col2"
}
}
}', '$.columns.col2', ['ALWAYS_RETURN_LIST']) AS output;
Failed to invoke function apoc.convert.getJsonPropertyMap : Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.util.LinkedHashMap<java.lang.Object,java.lang.Object> out of START_ARRAY token at [Source: UNKNOWN; line: -1, column: -1] |
---|
Also, we could leverage the apoc.json.validate
procedure (provided with APOC full) to handle incorrectly formatted JSONs by continuing the execution instead of causing it to fail.
For example, the following query returns 0 instead of failing due to InputCoercionException: Numeric value (18446744062065078016838) out of range
:
WITH '{
"foo": ["1", {"bar": 18446744062065078016838}, {"baz": 18446744062065078016838} ],
"baz": 7
}' as json
CALL { WITH json CALL apoc.json.validate(json) YIELD value RETURN collect(value) AS errs }
RETURN CASE errs WHEN [] THEN apoc.convert.fromJsonMap(json, '$', []) ELSE 0 END AS value