new TopicSpecification(type [, properties])
Topic specifications provide the information required to create a topic. Topics can be created from a topic specification using Session.topics#add.
Topic specifications allow an application to introspect the type and capabilities of a topic. Topic specifications are provided to ValueStreams and topic notification listeners.
A topic is specified in terms of its type and a map of optional property settings which can alter the default behavior of the topic.
Topic Properties
Depending on the topic type, some properties must be included in the specification when creating a topic and some properties have no effect. All topic specification property values must be supplied as strings.
The required and optional properties for each topic type are set out in the following table.
| STRING JSON BINARY |
DOUBLE INT64 |
ROUTING | SLAVE | TIME_SERIES | RECORD_V2 | |
|---|---|---|---|---|---|---|
| COMPRESSION | Optional | - | Optional | Optional | Optional | Optional |
| CONFLATION | Optional | Optional | Optional | Optional | Optional | Optional |
| DONT_RETAIN_VALUE | Optional | Optional | — | — | Optional | Optional |
| PUBLISH_VALUES_ONLY | Optional | — | — | — | Optional | Optional |
| SCHEMA | — | — | — | — | — | Optional |
| SLAVE_MASTER_TOPIC | — | — | — | Required | — | — |
| TIDY_ON_UNSUBSCRIBE | Optional | Optional | Optional | Optional | Optional | Optional |
| TIME_SERIES_EVENT_VALUE_TYPE | — | — | — | — | Required | — |
| TIME_SERIES_RETAINED_RANGE | — | — | — | — | Optional | — |
| TIME_SERIES_SUBSCRIPTION_RANGE | — | — | — | — | Optional | |
| VALIDATE_VALUES | Optional | Optional | — | — | Optional | — |
| PERSISTENT | Optional | Optional | — | — | Optional | — |
| REMOVAL | Optional | Optional | — | — | Optional | — |
| OWNER | Optional | Optional | — | — | Optional | — |
‡ Prefer the RECORD_V2 topic type for Diffusion record data since it provides full support for topic specifications.
Parameters:
| Name | Type | Argument | Default | Description |
|---|---|---|---|---|
type |
diffusion.topics.TopicType | The topic type for this specification. |
||
properties |
Object |
<optional> |
{} | The properties to use for this specification. |
- Since:
-
- 5.9
Examples
Properties can be set when creating the specification by passing an object
// Create specification, to be used for creating JSON topics which validate update values on the server
const TopicSpecification = diffusion.topics.TopicSpecification;
var specification = new TopicSpecification(diffusion.topics.TopicType.JSON, {
"VALIDATE_VALUES" : "true"
});
New specifications can be created with additional properties
// Create specification, to be used for creating JSON topics which validate update values on the server
const TopicSpecification = diffusion.topics.TopicSpecification;
var specification = new TopicSpecification(diffusion.topics.TopicType.JSON)
.withProperty(TopicSpecification.VALIDATE_VALUES, "true");