JSDoc: Class: DataProvider

new DataProvider

Data provider constructor.
The created object allows you to interact with Lightstreamer Server through the Adapter Remoting Infrastructure protocol as a Remote Data Adapter. See the ARI Protocol documentation for details on the request and response messages.
This object extends the EventEmitter object and emits the following events:

init: function(request, response) {}
Here, the request object is an associative array with the following content: {parameters: {<name 1>: <value 1> ... <name n>: <value n>}}
subscribe: function(itemName, response) {}
unsubscribe: function(itemName, response) {}

The response argument is a DataResponse object and one of its methods, error or success, must be called in order to reply to the request bound to the event. In case of a subscribe event, after calling the "success" callback, it is possible to invoke "update" or other item-related methods, or to predispose for future invocations when data is available. Then, upon an unsubscribe event, any existing such predisposition should be deactivated before calling the "success" callback.

Parameters:

Name	Type	Argument	Description
`stream`	Stream		the stream channel to the remote LS Proxy Data Adapter. In case of interruption, the 'error' event on the stream may report interruption cause details.
`isSnapshotAvailable`	Function	<optional>	optional callback that receives an itemName as argument and must return a boolean value asserting if the item supports snapshot. The default value is function(itemName) {return false;}
`credentials`	Object	<optional>	optional credentials to be submitted to the remote LS Proxy Data Adapter. The credentials are needed only if the Proxy Adapter is configured to require Remote Adapter authentication. If needed, the supplied object should contain both a "user" and a "password" field.
`keepaliveInterval`	Number	<optional>	optional time in milliseconds between subsequent keepalive packets to be sent on the reply stream to prevent LS Proxy Data Adapter and any intermediate nodes from closing the connection for inactivity; a value of 0 or negative means no keepalives; the default if not supplied is 10000 ms. However, if a stricter interval is requested by the Proxy Adapter on startup, it will be obeyed (with a safety minimum of 1 second). This should ensure that the Proxy Adapter activity checks will always succeed, but for some old versions of the Proxy Adapter. The keepalives can also allow for prompt detection of connection issues.

Method Summary

clearSnapshot: Sends a clear snapshot message for a particular item to the remote LS proxy.
declareFieldDiffOrder: Sends information about "diff" algorithms for some or all fields of a particular item.
endOfSnapshot: Sends an end of snapshot message for a particular item to the remote LS proxy.
failure: Sends a failure message to the remote LS proxy.
getStream: Returns the configured stream.
update: Sends an update for a particular item to the remote LS proxy.

Method Detail

<inner> clearSnapshot

Sends a clear snapshot message for a particular item to the remote LS proxy.

Parameters:

Name	Type	Description
`itemName`	String	the item name

<inner> declareFieldDiffOrder

Sends information about "diff" algorithms for some or all fields of a particular item. The algorithms suitable for each fields should be expressed as an array of string literals representing the actual algorithms in the desired order. Omitted fields or null arrays will add no information. On the other hand, an empty array can be supplied to mean that no "diff" algorithm is admitted for a field.

Parameters:

Name	Type	Description
`itemName`	String	the item name
`algorithmsMap`	Object	an associative array of algorithm lists, in turn expressed as a (possibly empty) array of string literals. Supported literals are: "JSONPATCH": Computes the difference between two values that are valid JSON string representations in JSON Patch format. "DIFF_MATCH_PATCH": Computes the difference between two values with Google's "diff-match-patch" algorithm (the result is then serialized with the custom "TLCP-diff" format). This algorithm applies to any strings, only provided that their UTF-16 representation doesn't contain surrogate pairs.

<inner> endOfSnapshot

Sends an end of snapshot message for a particular item to the remote LS proxy.

Parameters:

Name	Type	Description
`itemName`	String	the item name

<inner> failure

Sends a failure message to the remote LS proxy.

Parameters:

Name	Type	Description
`exception`	String	the exception message

<inner> getStream

Returns the configured stream.

Returns:

Object the stream

<inner> update

Sends an update for a particular item to the remote LS proxy.

Parameters:

Name	Type	Description
`itemName`	String	the item name
`isSnapshot`	Boolean	is it a snapshot?
`data`	Object	an associative array of strings that represents the data to be published