`json_extract_path`

Extract a nested JSON value from a context field and write it to a new context key.

Parameters

source_keystringrequired: Context key containing the source JSON value
pathstringrequired: Path to extract (supports dotted fields and array indexes, for example user.profile.name or items[0].id)
output_keystringrequired: Context key where the extracted value is written
requiredbooldefault false: If true, missing path causes a node failure
defaultanydefault null: Value to write when path is missing and required = false
parse_jsonbooldefault false: If source is a JSON string, parse it before extraction

Context Output

{output_key} -- extracted value, or default/null/error when not found

Example

local flow = Flow.new("json_extract_path_example")

-- Pull nested JSON from a public sample endpoint
flow:step("sample", nodes.http_get({
    url = "https://httpbin.org/json",
    output_key = "payload"
}))

flow:step("extract_title", nodes.json_extract_path({
    source_key = "payload_data",
    path = "slideshow.title",
    output_key = "slide_title"
})):depends_on("sample")

flow:step("extract_first_slide", nodes.json_extract_path({
    source_key = "payload_data",
    path = "slideshow.slides[0].title",
    output_key = "first_slide_title"
})):depends_on("sample")

flow:step("extract_missing_with_default", nodes.json_extract_path({
    source_key = "payload_data",
    path = "slideshow.missing.field",
    output_key = "missing_field",
    required = false,
    default = "not_present"
})):depends_on("sample")

flow:step("log", nodes.log({
    message = "Title: ${ctx.slide_title} | First slide: ${ctx.first_slide_title} | Missing: ${ctx.missing_field}",
    level = "info"
})):depends_on("extract_missing_with_default")

return flow