The array is enclosed within a pair of square brackets:  "items": [ ... ]. The GET_KEYS function returns an object type of JSON_KEY_LIST, which is a varray of VARCHAR2(4000). This specifies that this value is a number or of type numeric. In cases where you do not want the reference semantics, you can use the clone function to create a copy of the returned object. This tells you that the value is a single element, not an array of elements or values. The varray contains the names of keys in the JSON object. This means that if the returned JSON_ELEMENT_T is modified, then the containing JSON_ELEMENT_T is also changed. The "location" is still a Group which is fine; each event record should have (one) location and the coordinate values can legitimately be organized as children within a sub-structure. If the provided input is not valid JSON, then an error message is raised. Specifying "items" as the JSON Object Name tells the input to handle the data as an array of values and to ingest each item from the array as its own event record. It appears, looking at the data, that the last value in each list is the most recent calibration date. APIs are powerful ways to access data and more specifically the specific type and subset of data that you need for your analysis, programmatically. Sometimes developing such a Python "bridge" between a data provider and GeoEvent Server to perform some simple data manipulation or clean-up is easier than using the GeoEvent Server Java SDK to develop a custom inbound adapter or processor. GEOJSON can be used to create maps just like shapefiles can. The cardinality of "location", however, is One not Many. Is it possible to reference this data using something like "data.stations.station_id"  for example? JSON can store any of the following data types: Note that in the example below - the word “Chaya” which is the value associated with name is in quotes "". Remember, the data was received as a single event record and "items" is a list or array of elements. What do we mean when we refer to a "hierarchical" JSON structure? The function takes as input VARCHAR2, CLOB, or BLOB data, and returns a JSON_ELEMENT_T instance. You will also explore the machine readable JSON data structure. Like this: The ability to store nested or hierarchical data within a text file structure makes JSON a powerful format to use as you are working with larger datasets. When clicking the "node hierarchy" icon – to the left of the pencil when the attribute is of type 'Group' – I've had the GeoEvent Manager pop back out to the 'Group' level after editing one of the attributes nested beneath the group. First, the cardinality of the "calibrated" event attribute needs be changed from One to Many (since its value is now an array or list rather than a single date/time value). Thus, the GET_STRING function returns a non-null value even if IS_STRING returns false. The input LOB cannot be NULL. The introspection functions are: The return value of the get_size function depends on the JSON type: For an object, it returns the number of keys. The GET_STRING function converts the value to a string if it is not already a string. Also, Google Protocol Buffers can fill this role, although it is not a data interchange language. JSON_SCALAR_T Object Type. GeoEvent Server does require that every value in the array be the same type (e.g. If you've no influence over the data provider, you might want to consider writing a Python script (or something similar) to take the data being offered and restructure it into something that GeoEvent Server is able to ingest. Raise an error if the data types do not match, for example, if you call GET_NUMBER on a string value. These three items have significantly different geographic locations, so we should find a way to ingest them as three separate event records. "node hierarchy" icon again to dive back into the group and add/edit another attribute within the group. The following procedures append the specified value to the end of the JSON array: Introspection enables you to discover properties of the JSON array without modifying them. JSON_ELEMENT_T is the supertype for the JSON_OBJECT_T, JSON_SCALAR_T, and JSON_ARRAY_T object types. This type is used by the get_Keys function in the JSON_OBJECT_T Object Type. Is every record in the "items" list required to have the same number of reported maintenance visits? You cannot refer to items.location.latitude because you have not specified an index to select one of the three elements in the "items" array. It appears, looking at the data, that the last value in each list is the most recent calibration date. To reset the behavior to the default, you can call on_Error(0). That answers the first question - integration will occur via REST with the vendor sending data as an HTTP/POST request to a GeoEvent Server endpoint. Just make sure that the field is Date formatted in the input GE Definition. The input has to specify a JSON object, not an array. Also, when the block of JSON data illustrated above is sent to the input via HTTP/POST, the input's event count only increments by one, indicating that only one event record was received. What do we mean when we refer to a "multi-cardinal" JSON structure? After completing this tutorial, you will be able to: You will need a computer with internet access to complete this lesson. See the Reference Semantics section below for details. What does a typical JSON data record look like? The following procedures enable you to set the value at the specified position in the JSON array. Each event record also has a date/time the item was last "calibrated" (expressed as an epoch long integer in milliseconds). For instance, EMPTY_LOB can be provided. You cannot refer to, If the illustrated JSON data were representative of data you wanted to ingest, you should specify an explicit value for the, The first thing you should notice, when the illustrated. Result: "{""x"":32.125,""y"":-117.125,""spatialReference"":{""wkid"":4326}}". Does the "calibrated" attribute's type change from. In the first illustration above, sensor 5416 has only been calibrated once, but the other two sensors have been calibrated multiple times. JSON is a syntax for storing and exchanging data. Values associated with "id", "status", and "calibrated" are simple numeric, string, or Boolean values. In the previous lesson, you learned how to access human readable text files data programmatically using: You also learned how to use getURL() for urls that are both secure (https) and less secure (http). To cast a JSON_ELEMENT_T into a subtype (for example, JSON_OBJECT_T), you need to perform an explicit cast using TREAT AS. StackExchange - How can I convert a UNIX timestamp to a datetime format within the GeoEvent. When I first mentioned configuring a Receive JSON on a REST Endpoint input to allow the illustrated block of JSON to be ingested into GeoEvent Server for processing, I indicated that the JSON Object Name property should be left unspecified. Assuming extraction of the most recent calibration date was required, your best option in this case would be to use the ArcGIS GeoEvent Server SDK to develop a custom processor which implemented a list iterator, or work with the data provider to see if the data schema could be modified to provide the most recent calibration date as a data value whose cardinality was One rather than Many. See Also:  What time is it? But you cannot use a, Assuming extraction of the most recent calibration date was required, your best option in this case would be to use the, The above reference from Stack Exchange is a little dated (2016). Fire / Spectral Remote Sensing Data in R, 8.1 Fire / spectral remote sensing data - in R, https://zenodo.org/badge/latestdoi/143348761. The description of how the "JSON Object Name" is used was a great help and was difficult to find anywhere else. It corresponds to the JSON object structure. You cannot create an empty JSON_ELEMENT_T instance. So, the combination of setting the data type on the Input connector to Date (default is Double for this type of data in the generated GeoEvent Definition) - you need to multiply the date field in question by 1000 in a field calculator, due to GeoEvent expecting milliseconds, not seconds. A little unsure how to handle the 'Expected Date Format' for these dates (sent in 'seconds since 1970' format). In this lesson, the getURL() function will become more valuable to us as you parse data accessed from an API. Error: You don't have JavaScript enabled. Working with the structure specified in the GeoEvent Definition illustrated above, if you wanted to access the coordinate values for "latitude" or "longitude" you would have to specify which latitude and longitude you wanted. A custom processor could, but that's a lot of overhead to assume and I'd only take that approach if there was no other way. But you cannot use a Field Mapper Processor in GeoEvent Server, for example, to extract the last value from each event record's "calibration" list -- you don't know how many values will be in each array, so you cannot use an index to access a particular value. Long, String, Date, ..., or Group), but that's not an issue in this case as all the values are epoch long integer representations of date values in milliseconds. Notice the cardinality of … For an array, it returns the number of items. Also notice that, in this configuration, "items" is a Group element type. In the following example, an error is raised because the value of “a” is “xyz”, which cannot be converted to a number. If the provided input is not a valid JSON object, then an error message is raised. Table 285-1 Values for the value Parameter in the ON_ERROR Procedure. JSON defines only two data structures: objects and arrays. This means that changing the returned value affects its container. It would be natural to think of each element as an event record with its own "id", "status", and "location". Second, you would need to remove the TIME_START tag from the element. Apart from XML, examples could include CSV and YAML (a superset of JSON). The "location" value, on the other hand, is an object which encapsulates two child values -- "latitude" and "longitude". Refine R Markdown Reports with Images and Basemaps, 5. JSON_ELEMENT_T Object Type. One advantage to handling each "calibrated" element as a variable length array is that individual records are not required to have the same number of maintenance date/time values recorded. For GeoEvent Server, it is important that both the array have a name and that each object within the array have a homogeneous structure, meaning that every event record should, generally speaking, use a common schema or collection of name/value pairs to communicate the item's data.

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