The Poll an External Website for GeoJSON input connector can be used to retrieve and adapt event data, formatted as GeoJSON, from an external website. For more information and examples of GeoJSON data record formatting, see the GeoJSON specification.
When multiple event data records are returned from a web server or web service, they should be organized as a FeatureCollection, as illustrated below. The GeoJSON Inbound Adapter will handle each feature record in the FeatureCollection as a separate event data record.
Usage notes
Keep the following in mind when using the Poll an External Website for GeoJSON input connector:
- Use this input connector to query a web server or web service for data, formatted as GeoJSON, and adapt it to create event records for processing.
- This input connector pairs the GeoJSON inbound adapter with the HTTP inbound transport.
- A GeoJSON feature record is expected to contain both geometry and properties members.
- Typical event records, organized as a part of a GeoJSON FeatureCollection, are illustrated above.
- The adapter will manage both single GeoJSON feature records and GeoJSON FeatureCollection records.
- Like feature JSON, GeoJSON is a subtype of generic JSON. Various GeoEvent Server adapters are used to process these specific formats.
- For more information and examples of GeoJSON data record formatting, see the GeoJSON specification.
- The adapter does not support the Construct Geometry from Fields capability.
- The HTTP Method parameter specifies the type of HTTP request used to query a web service for data. The default is to use an HTTP/GET request.
- Query parameters can be specified using the Parameters parameter to help select data of interest.
- Specifying query parameters as part of an HTTP/GET request can improve performance by narrowing the number of items returned.
- The name and values of any specified query parameter depend on what requests are supported by the external web service.
- This input connector assumes the external web server or web service will accept HTTP/GET requests without requiring authentication. For external websites requiring authentication, consider creating a custom input connector that pairs the Generic JSON inbound adapter with an HTTP inbound transport that supports basic, certificate, or OAuth authentication.
- The Receive New Data Only parameter is used to request that a feed return only previously unobserved or newly updated data. This capability depends on the data feed correctly incorporating Last-Modified into the header of its response to an HTTP request. If the response header does not indicate a date or time the content was last updated, GeoEvent Server will assume that data in the response represents new or recently updated data. You can read more about the use of Last-Modified in response headers in the RFC 7232 HTTP specification.
Parameters
The following are the parameters for the Poll an External Website for GeoJSON input connector:
| Parameter | Description |
|---|---|
Name | A descriptive name for the input connector used for reference in GeoEvent Manager. |
URL | The base URL of the external website hosting the data as GeoJSON. GeoEvent Server will issue a poll request to the URL to retrieve the GeoJSON data. |
Create GeoEvent Definition | Specifies whether a new or existing GeoEvent Definition should be used for the inbound event data. A GeoEvent Definition is required for GeoEvent Server to understand the inbound event data attribute fields and data types.
|
GeoEvent Definition Name (New) (Conditional) | The name assigned to a new GeoEvent Definition. If a GeoEvent Definition with the specified name already exists, the existing GeoEvent Definition will be used. The first data record received will be used to determine the expected schema of subsequent data records, a new GeoEvent Definition will be created based on that first data record's schema. The parameter is shown when Create GeoEvent Definition is set to Yes and is hidden when set to No. |
GeoEvent Definition Name (Existing) (Conditional) | The name of an existing GeoEvent Definition to use when adapting received data to create event data for processing by a GeoEvent Service. The parameter is shown when Create GeoEvent Definition is set to No and is hidden when set to Yes. |
HTTP Method | The HTTP request method to use when GeoEvent Server polls the external server providing the data feed. The default is to use an HTTP/GET request.
|
Post From Post Body Post body MIME Type Post Parameters (Conditional) | These parameters are hidden, by default, when the HTTP Method is set to Get. For more information, see the Limitations below. |
Default Spatial Reference | The well-known ID (WKID) or well-known text (WKT) of a spatial reference system in which the geometry's coordinates are expressed. This parameter has no default value. This is a deprecated parameter. The GeoJSON specification states that all coordinates be expressed in a geographic coordinate reference system, using the World Geodetic System 1984 (WGS 84) datum, with longitude and latitude units of decimal degrees. |
Receive New Data Only | Specifies whether the adapter will look for a Last-Modified value in the data feed response’s header and will attempt to use this value to avoid processing data already been received and not updated. The parameter’s name can be misleading. The transport will always receive whatever data a feed includes in its response to the connector’s query. When Receive New Data Only is specified, however, the transport will cache the date/time of its last request and will only relay data it receives to the adapter if the response from the data feed includes a Last-Modified value that is greater-than the transport’s cached value. Specifying a Last-Modified value is optional. In practice, not many data feeds include it in their responses. The default for this parameter is Yes, but if a Last-Modified value is not found, the parameter is ignored as the date/time needed to determine whether data in the response is new or updated is not available.
For more information about the use of Last-Modified in response headers, see the RFC 7232 HTTP specification. |
Frequency (in seconds) | The interval (in seconds) an external web server or web service will be polled for data. The default is 10 seconds (one poll request will be made every 10 seconds). |
Header Parameter Name:Value List | The parameters to include in a request’s HTTP header when an external web server or web service is polled. The header parameters should be specified using Name:Value pairs (colon included) separated by commas. |
Parameters | Specifies a query parameter (or multiple query parameters) to append to the base URL. Query parameters are specific to each web service and are not supported by all services. When supported, query parameters help specify data of particular interest. This parameter has no default value. Query parameters are normally incorporated into the URL parameter. |
Use URL Proxy | Specifies whether GeoEvent Server will use a URL proxy when making its HTTP requests. The default is No.
|
URL Proxy (Conditional) | The URL proxy to use when making an HTTP request. The parameter is shown when the Use URL Proxy is set to Yes and is hidden when set to No. |
Expected Date Format | The pattern used to match expected string representations of date/time values and convert them to Java Date values. The pattern's format follows the Java SimpleDateFormat class convention. While GeoEvent Server prefers date/time values to be expressed in the ISO 8601 standard, several string representations of date/time values commonly recognized as date values can be converted to Java Date values without specifying an Expected Date Format pattern. These include the following:
If the date/time values received are expressed using a convention other than one of the five shown above, you will have to specify an expected date format pattern so GeoEvent Server knows how the date/time values should be adapted. |
Acceptable MIME Types (Client Mode) (Conditional) | Specifies the MIME types this connector will accept when receiving a response to its query to a data feed. The external web service’s response specifies the actual MIME types for any data sent to GeoEvent Server. This connector understands the following MIME types, which are the default for this parameter: text/json,application/json For more information on official MIME types, see Internet Assigned Numbers Authority (IANA). For more information on the MIME types not used by ArcGIS Server, see MIME types not used by ArcGIS Server. This parameter is shown when the HTTP Method is set to Get and is hidden when set to either Post or Put. |
HTTP Timeout (in seconds) | Specifies the maximum time (in seconds) the input connector will wait for a response from the external web service it has queried. The value must be an integer between 1 and 2147483. The default value is 30 seconds (the HTTP request will timeout after 30 seconds if no response is received). |
Considerations and limitations
Always use an HTTP/GET request, which does not include a Content-Body, for polling input, and use query parameters to specify data of interest. The parameters below are only applicable to output connectors that send data to an external web server or web service. Ensure that the HTTP Method parameter is set toHTTP/GET (the default) for the parameters below to remain hidden.
| Parameter | Description |
|---|---|
Post From (Conditional) | Specifies whether this connector will use an HTTP/POST or HTTP/PUT request.
The parameter is shown when HTTP Method is set to either Post or Put and is hidden when set to Get. |
Post Body (Conditional) | Specifies data to include in the Content-Body of an HTTP/POST or HTTP/PUT request. The parameter is shown when Post From is set to Content Body and is hidden when set to Parameters. |
Post body MIME Type (Conditional) | Specifies the MIME type of data included in the HTTP request’s Content-Body. MIME types typically consist of a type/subtype structure and are used to specify the internet media types used and accepted by an HTTP client/server. The parameter is shown when Post From is set to Content Body and is hidden when set to Parameters. |
Post Parameters (Conditional) | Specifies parameters to include as part of the HTTP request. Parameters should be specified using Name:Value pairs (colon included) separated by commas. This parameter has no default value. The parameter is shown when Post From is set to Parameters and is hidden when set to Content Body. |