

API Docs - v4.0.36

Sinkmapper

json (Sink Mapper)

This extension is an Event to JSON output mapper.
Transports that publish messages can utilize this extensionto convert Siddhi events to JSON messages.
You can either send a pre-defined JSON format or a custom JSON message.

Syntax

@sink(..., @map(type="json", validate.json="<BOOL>", enclosing.element="<STRING>")

QUERY PARAMETERS

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
validate.json	If this property is set to `true`, it enables JSON validation for the JSON messages generated. When validation is carried out, messages that do not adhere to proper JSON standards are dropped. This property is set to 'false' by default.	false	BOOL	Yes	No
enclosing.element	This specifies the enclosing element to be used if multiple events are sent in the same JSON message. Siddhi treats the child elements of the given enclosing element as events and executes JSON expressions on them. If an `enclosing.element` is not provided, the multiple event scenario is disregarded and JSON path is evaluated based on the root element.	$	STRING	Yes	No

Examples EXAMPLE 1

@sink(type='inMemory', topic='stock', @map(type='json'))
define stream FooStream (symbol string, price float, volume long);

Above configuration does a default JSON input mapping that generates the output given below.
{
    "event":{
        "symbol":WSO2,
        "price":55.6,
        "volume":100
    }
}

EXAMPLE 2

@sink(type='inMemory', topic='{{symbol}}', @map(type='json', enclosing.element='$.portfolio', validate.json='true', @payload( """{"StockData":{"Symbol":"{{symbol}}","Price":{{price}}}""")))
define stream BarStream (symbol string, price float, volume long);

The above configuration performs a custom JSON mapping that generates the following JSON message as the output.
{"portfolio":{
    "StockData":{
        "Symbol":WSO2,
        "Price":55.6
      }
  }
}

Sourcemapper

json (Source Mapper)

JSON to Event input mapper. Transports which accepts JSON messages can utilize this extensionto convert the incoming JSON message to Siddhi event. Users can either send a pre-defined JSON format where event conversion will happen without any configs or can use json path to map from a custom JSON message.
In default mapping, json string of the event could be enclosed by the element "event" which is optional.

Syntax

@source(..., @map(type="json", enclosing.element="<STRING>", fail.on.missing.attribute="<BOOL>")

QUERY PARAMETERS

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
enclosing.element	Used to specify the enclosing element in case of sending multiple events in same JSON message. WSO2 DAS will treat the child element of given enclosing element as events and execute json path expressions on child elements. If enclosing.element is not provided multiple event scenario is disregarded and json path will be evaluated with respect to root element.	$	STRING	Yes	No
fail.on.missing.attribute	This can either have value true or false. By default it will be true. This attribute allows user to handle unknown attributes. By default if an json execution fails or returns null DAS will drop that message. However setting this property to false will prompt DAS to send and event with null value to Siddhi where user can handle it accordingly. (ie. Assign a default value)	true	BOOL	Yes	No

Examples EXAMPLE 1

@source(type='inMemory', topic='stock', @map(type='json'))
define stream FooStream (symbol string, price float, volume long);

Above configuration will do a default JSON input mapping.
For a single event, expected input should be in one of the following formats.
{
    "event":{
        "symbol":"WSO2",
        "price":55.6,
        "volume":100
    }
}

or

{
    "symbol":"WSO2",
    "price":55.6,
    "volume":100
}

EXAMPLE 2

@source(type='inMemory', topic='stock', @map(type='json'))
define stream FooStream (symbol string, price float, volume long);

Above configuration will do a default JSON input mapping.
For multiple events, expected input should be in one of the following formats.
[
{"event":{"symbol":"WSO2","price":55.6,"volume":100}},
{"event":{"symbol":"WSO2","price":56.6,"volume":99}},
{"event":{"symbol":"WSO2","price":57.6,"volume":80}}
]

or

[
{"symbol":"WSO2","price":55.6,"volume":100},
{"symbol":"WSO2","price":56.6,"volume":99},
{"symbol":"WSO2","price":57.6,"volume":80}
]

EXAMPLE 3

@source(type='inMemory', topic='stock', @map(type='json', enclosing.element="$.portfolio", @attributes(symbol = "company.symbol", price = "price", volume = "volume")))

Above configuration will perform a custom JSON mapping.
For a single event, expected input will look like below
.{
"portfolio":{
     "stock":{ "volume":100,
        "company":{
           "symbol":"WSO2"
       },
        "price":55.6
    }
}

EXAMPLE 4

@source(type='inMemory', topic='stock', @map(type='json', enclosing.element="$.portfolio", @attributes(symbol = "stock.company.symbol", price = "stock.price", volume = "stock.volume")))
define stream FooStream (symbol string, price float, volume long);

Above configuration will perform a custom JSON mapping.
For multiple events, expected input will look like below
.{"portfolio":
[ {"stock":{"volume":100,"company":{"symbol":"wso2"},"price":56.6}}, {"stock":{"volume":200,"company":{"symbol":"wso2"},"price":57.6}} ]
}