JSON (JavaScript Object Notation) Reader Parameters

Auto: The reader will examine the JSON dataset and decide how to produce features. If the dataset is a JSON array, the reader will produce a feature for each value in the array. If the dataset is a JSON object, the reader will produce a single feature whose attributes are created from the object keys.

JSON Query: Selecting this option enables the JSON Query for Feature Objects parameter, where you can indicate which JSON values should be converted into FME features.

This table configures how values in the JSON dataset are mapped to FME feature features. Each row of the table contains a feature type and a JSON query string. For each value in the JSON dataset that matches the JSON query, a feature will be created with the corresponding feature type.

Each cell in the Query column contains a button that opens a dialog containing the structure of the JSON dataset in a tree form. Selecting a value from the tree will populate the parameter with the appropriate query string to turn the selected values into features.

The query string may also be manually entered. The string uses a simple syntax to refer to values in the JSON dataset. The outermost JSON element, which must be an array or an object, is always referred to by the term json, and this term must appear at the beginning of every JSON query expression. The child elements can be referred to using JavaScript-like square bracket index operators. For example, if the outermost element is an array, the first element of the array can be referred to by the expression json[0], the second element can be referred to by the expression json[1], and so on. Likewise, if the outermost JSON element is an object, with keys "name" and "address", then the values of these keys can be referred to by the expressions json["name"] and json["address"], respectively.

These index operators can be cascaded. For example, if the outermost JSON element is an object with an "address" key whose value is an object containing keys "city" and "province", then these values can be referred to by the expressions json["address"]["city"] and json["address"]["province"].

In order to refer to all of the values in an array or object, a wildcard index * can be used. For example, if the outermost JSON element is an array, then the expression json[*] refers to every element in the array.

This parameter controls whether or not the reader should flatten nested JSON objects and arrays into multiple attributes, or keep them as JSON values. This option provides similar functionality to the JSONFlattener transformer.

For example, consider the following JSON:

{
      "id" : 456,
      "name" : {
         "first" : "Francisca",
         "last" : "Mitchell"
      }
}

When the parameter is set to Yes, this will become a single feature with attributes named id, name.first, and name.second.

Attribute(64 bit integer) : 'id' has value '456'

Attribute(encoded: utf-8) : 'name.first' has value 'Francisca'

Attribute(encoded: utf-8) : 'name.last' has value 'Mitchell'

Nested objects will be flattened into attributes, with the key names separated by a ‘.’ character. Nested array values will be flattened into list attributes.

When the parameter is set to No, the attributes will be id and name. The name attribute will have a string value containing a JSON object, the value of the ‘name’ key.

Attribute(64 bit integer) : `id' has value `456'

Attribute(encoded: utf-8) : `name' has value `{"first":"Francisca","last":"Mitchell"}'

Specifies the JSON object key that contains the feature type of the FME feature produced from the object.

If no value is provided, json_featuretype is used.

Specifies the geometry format that the reader should use when converting the value of Geometry Key Name into FME geometry.

Possible values are GeoJSON, OGC-WKT, and None. If no value is provided, GeoJSON is used.

Specifies the JSON object key that contains the geometry of the FME feature produced from the object. If no value is provided, json_geometry is used.

Specifies the JSON object key that contains the coordinate system. The default value is json_ogc_wkt_crs.

Yes: Each feature produced by the reader will contain a json_fragment attribute. This attribute will contain the entire JSON object or array from which the feature was created.

Use this parameter to expose Format Attributes in FME Workbench when you create a workspace:

• In a dynamic scenario, it means these attributes can be passed to the output dataset at runtime.
• In a non-dynamic scenario, this parameter allows you to expose additional attributes on multiple feature types. Click the browse button to view the available format attributes (which are different for each format) for the reader.

A search envelope (also known as a bounding box) is a rectangular area that defines a geographic area. In FME, the easiest way to define a search envelope is to use search envelope parameters.

Defining a search envelope is the most efficient method of selecting an area of interest because FME will read only the data that is necessary – it does not have to read an entire dataset. Search Envelope parameters apply to both vector and raster datasets and can be particularly efficient if the source format has a spatial index.

Most FME readers have parameters to define the search envelope of data that is being read:

The parameters include the x and y coordinates of the bounding box as well as a parameter that defines the coordinate system.

How to Define the Bounding Box

Using the minimum and maximum x and y parameters, define a bounding box that will be used to filter the input features. Only features that intersect with the bounding box are returned. Note that the bounding box intersection is not a full geometry intersection (based on spatial relationships) that would be returned by a transformer like the SpatialFilter.

Search Envelope Coordinate System

Specifies the coordinate system of the search envelope if it is different than the coordinate system of the data. The coordinate system associated with the data to be read must always be set if this parameter is set.

If this parameter is set, the minimum and maximum points of the search envelope are reprojected from the Search Envelope Coordinate System to the reader’s coordinate system prior to applying the envelope.

The underlying function for Use Search Envelope is an intersection; however, when Clip to Search Envelope is checked, a clipping operation is also performed.

• When checked (set to Yes), this option instructs FME to clip features to the exact envelope boundary. FME removes any portions of imported features being read that are outside the search envelope.
• When left unchecked (set to No), features that overlap the boundary will be included in their full (unclipped) form.

Specify the authentication method to use when accessing a password-protected server.

• Basic (default) – Basic access authentication is designed to allow a client to provide credentials to a server on the assumption that the connection between them is trusted and secure. Note that any credentials passed from client to server can be easily intercepted through an insecure connection.
• Digest – Digest authentication is one of the agreed-upon methods a web server can use to negotiate credentials, such as username or password, with a user's web browser.
• NTLM – A challenge-response protocol that is used to provide compatibility with versions of Windows earlier than the Windows 2000 operating systems.
• Web Connection – Web connections provide a convenient and secure way to store and reuse previously established connection parameters. See Web Connection below.
• Single Sign-on – FME will use the credentials of the current user to authenticate the HTTP request. This authentication method currently works only on the Windows operating system.

Using Web Connections

FME Options: Web Connections