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json (Source Mapper)

This extension is a JSON-to-Event input mapper. Transports that accept JSON messages can utilize this extension to convert an incoming JSON message into a Stream App event. Users can either send a pre-defined JSON format, where event conversion happens without any configurations, or use the JSON path to map from a custom JSON message. In default mapping, the JSON string of the event can be enclosed by the element "event", though optional.

Syntax

CREATE SOURCE <NAME> WITH (map.type="json", enclosing.element="<STRING>", fail.on.missing.attribute="<BOOL>")

Query Parameters​

NameDescriptionDefault ValuePossible Data TypesOptionalDynamic
enclosing.elementThis is used to specify the enclosing element when sending multiple events in the same JSON message. Mapper treats the child elements of a given enclosing element as events and executes the JSON path expressions on these child elements. If the enclosing.element is not provided then the multiple-event scenario is disregarded and the JSON path is evaluated based on the root element.\$STRINGYesNo
fail.on.missing.attributeThis parameter allows users to handle unknown attributes.The value of this can either be true or false. By default it is true. If a JSON execution fails or returns null, mapper drops that message. However, setting this property to false prompts mapper to send an event with a null value to Stream App, where users can handle it as required, ie., assign a default value.)trueBOOLYesNo

Example 1​

CREATE SOURCE FooStream WITH (type='inMemory', topic='stock', map.type='json') (symbol string, price float, volume long);

This configuration performs a default JSON input mapping. For a single event, the input is required to be in one of the following formats: { "event":{ "symbol":"gdn", "price":55.6, "volume":100 } } or { "symbol":"gdn", "price":55.6, "volume":100 }

Example 2​

CREATE SOURCE FooStream WITH (type='inMemory', topic='stock', map.type='json') (symbol string, price float, volume long);

This configuration performs a default JSON input mapping. For multiple events, the input is required to be in one of the following formats: [ {\"event\":{\"symbol\":\"gdn\",\"price\":55.6,\"volume\":100}}, {\"event\":{\"symbol\":\"gdn\",\"price\":56.6,\"volume\":99}}, {\"event\":{\"symbol\":\"gdn\",\"price\":57.6,\"volume\":80}} ] or [ {\"symbol\":\"gdn\",\"price\":55.6,\"volume\":100}, {\"symbol\":\"gdn\",\"price\":56.6,\"volume\":99}, {\"symbol\":\"gdn\",\"price\":57.6,\"volume\":80} ]

Example 3​

CREATE SOURCE FooStream WITH (type='inMemory', topic='stock', map.type='json', map.enclosing.element="$.portfolio", map.attributes="symbol = 'company.symbol', price = 'price', volume = 'volume'")

This configuration performs a custom JSON mapping. For a single event, the expected input is similar to the one shown below: { "portfolio":{ "stock":{ "volume":100, "company":{ "symbol":"gdn" }, "price":55.6 } } }

Example 4​

CREATE SOURCE FooStream WITH (type='inMemory', topic='stock', map.type='json', map.enclosing.element="$.portfolio", map.attributes="symbol = 'stock.company.symbol', price = 'stock.price', volume = 'stock.volume'") (symbol string, price float, volume long);

The configuration performs a custom JSON mapping. For multiple events, expected input looks as follows. .{"portfolio": [ {\"stock\":{\"volume\":100,\"company\":{\"symbol\":\"gdn\"},\"price\":56.6}}, {\"stock\":{\"volume\":200,\"company\":{\"symbol\":\"gdn\"},\"price\":57.6}} ] }