...

The KeyValue feature allows to read, process and write data as key-value pairs, which don't have an fixed schema like tuples.

To use the feature you have to install it and use the "KeyValueObject" or "NestedKeyValueObject" data handler. The applicable operators will be automatically chosen. Until now selection and projection are supported. Also there are operators to transform key-value objects to tuples and the other way round. The feature also includes wrapper for handling of JSON and BSON data.

Operators

The following new or modificated operators are provided in keyvalue feature.

KeyValueToTuple (Deprecated, use ToTuple operator instead.)

Transforms key-value object to tuples. Use the SCHEMA attribute to define:

...

          ['$','root','KeyValueObject'],
          ['monday', 'List(Integer)'],
          ['$..monday.length()','MondaySize','mondayCount','Integer'],
          ['$.uuid', 'String'],
          ['$.monday[0]',MondayFirst, 'Integer'],

...

WIth the type field you can set the type of the tuple.

#DEFINE SCHEMA [['timestamp.unixtimestamp', 'List(Integer)'],['timestamp.iso', 'String'],['track.name', 'String']]
tuple = KEYVALUETOTUPLE({schema=${SCHEMA}, TYPE = 'type'}, receiverJSON)

TupleToKeyValue

Transforms tuples to key-value objects based on the tuples schema.

...

There are some MEP-Functions that can be used in the MAP-Operator:

• KeyValueObject: asKeyValue(Object kv): Cast an object to a KeyValueObject (could be necessary if Odysseus can not determine the type of an object). KV must be a KeyValueObject, else there will be a ClassCastException
• KeyValueObject: toKeyValue(String): Creates a new KeyValueObject from a String JSON Expression
• Object: getElement(KeyValueObject kv, String path): Returns the one element identified by the path expression. 
• Tuple: getElements(KeyValueObject kv, String path): Returns a tuple of elements identified by the path expression.
• Object: path(KeyValueObject kv, String path): Returns the one object that is identified by the JSONPATH epxression. Slower than getElement(s) but more expressive.TODO

Wrapper

The feature adds protocol handler for the common key-value data formats JSON and BSON (binary JSON).

...

 SENDERjson = SENDER({
    transport='TCPServer',
    wrapper='GenericPush',
    protocol='JSON',
    dataHandler='KeyValueObject',
    SINK="SENDERjson",
    options=[
        ['port', '8080'],
        ['HOST','localhost'],
    ]}, json)
receiverJSON = RECEIVE({
    transport='TCPClient',
    source= 'ReceiverJSON',
    protocol='JSON',
    dataHandler='KeyValueObject',
    options=[['port', '8080']]         
})

BSON

BSON can be used in exactly the same way as JSON - just replace the protocol handler.

...