JSONObjectBuilder

Builds a JSON object from feature attributes, or inserts attribute values into an existing JSON object.

The transformer operates in one of two Build Modes:

Create new JSON Object: Constructs a new JSON object on each feature.
Insert into Existing JSON Object: Inserts attribute values into an already existing JSON object at the location specified by the JSON Pointer to Insert Location parameter.
If the key matching the final token in the pointer does not exist at the specified location, the transformer will create that key and initialize it as a new object before inserting the attribute values.

JSON Pointers

A JSON pointer is a simple mechanism to refer to values within a JSON document. It is defined by RFC 6901 and consists of a sequence of tokens separated by forward slashes (/). Each token selects an object key or array index. An empty JSON Pointer refers to the root JSON value. For example, given the JSON document:

Copy

{
  "metadata": {
    "title": "Value List",
    "count": 2
  },
  "items": [
    { "id": "a", "label": "Alpha", “tags”: [2, 7] },
    { "id": "b", "label": "Bravo", “tags”: [3, 4] }
  ]
}

The following JSON Pointers evaluate as:

“”	The entire object
“/metadata”	{ "title": "Value List", "count": 2 }
“/metadata/count”	2
“/items/0”	{ "id": "a", "label": "Alpha", “tags”: [2, 7] }
“/items/1/tags”	[3, 4]

The JSON pointer is used by this transformer to select the target JSON object where selected attributes will be inserted as key-value pairs.

In Insert into Existing JSON Object mode, the pointer must identify an existing object, or a location where an object can be created at the final token. Otherwise the insert location is considered unresolvable (for example, when the pointer refers to an array or non-object value) and the key value pairs will not be inserted.

For more details, see JSON Pointer to Insert Location.

See JavaScript Object Notation (JSON) Pointer at the IETF (RFC 6901).

Usage Notes

To append values to a JSON array, use the JSONAppender.
To assemble larger JSON documents, combine the JSONObjectBuilder with the JSONAppender.

Configuration

Input Ports

Output Ports

Parameters

General

Build Mode

Select the operating mode:

Create new JSON Object: Builds a new JSON object from the selected attributes on each feature.
Insert into Existing JSON Object: Inserts the selected attribute values into an existing JSON object.

JSON Object Input

Only applicable for Insert into Existing JSON Object mode. Selecting from the list enables that selection’s corresponding parameter:

Attribute with JSON Object: Choose the attribute containing the existing JSON object.
JSON Object Filename: Browse to the JSON file.

JSON Pointer to Insert Location

Only applicable for Insert into Existing JSON Object mode. A standard RFC 6901 JSON Pointer is used to identify the location in the JSON object where the new key value pairs will be inserted. The parameter’s default value is an empty string, which refers to the root of the object.

Consider the following JSON Object:

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{
  "experiment": {
    "id": "EXP-01",
    "trials": [
      { "number": 1, "signals": ["a", "b"] },
      { "number": 2, "signals": ["c"] }
    ]
  }
}

And the following selected attributes:

status = “ok”

notes{0} = “n0”

notes{1} = “n1”

If the pointer resolves to an existing object, the attributes are inserted into that object. For example, using the pointer /experiment/trials/0 produces:

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{
  "experiment": {
    "id": "EXP-01",
    "trials": [
      {
        "number": 1,
        "signals": ["a", "b"],
        "status": "ok",
        "notes": ["n1", "n2"]
      },
      {
        "number": 2,
        "signals": ["c"]
      }
    ]
  }
}

If all Pointer tokens exist in the document except for the last token, the transformer will create a new key from the final token, initialize it as a new JSON object, and insert the selected attributes into the newly created object. For example using the pointer /experiment/summary produces:

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{
  "experiment": {
    "id": "EXP-01",
    "trials": [
      {
        "number": 1,
        "signals": ["a", "b"]
      },
      {
        "number": 2,
        "signals": ["c"]
      }
    ],
    "summary": {
      "status": "ok",
      "notes": ["n1", "n2"]
    }
  }
}

If the pointer does not resolve to an existing object and a new object cannot be created under the final key, the insert location is considered unresolvable. This can occur when the portion of the pointer preceding the final token does not exist (e.g. /experiment/run/summary) or when the pointer refers to something other than an object, such as an array (/experiment/trails) or a non-object value (/experiment/id).

In this case, the key value pairs will not be inserted, and the feature will be routed unchanged to the Output port.

Members

Attribute	The feature attributes to include in the JSON object. Table row ordering controls the order in which keys are written. List attributes are supported and will be written as JSON arrays. When multiple list attributes share the same list path, the attributes are grouped by list index into array elements. For example, given the following attributes: outer{0}.id = 1 outer{1}.id = 2 outer{0}.inner{0}.code = A outer{0}.inner{1}.code = B outer{1}.inner{0}.code = C selecting outer{}.id and outer{}.inner{}.code produces: Copy { "outer": [{ "id": 1, "inner": [{ "code": "A" }, { "code": "B" } ] }, { "id": 2, "inner": [{ "code": "C" } ] } ] }
Type	Specifies the type for an attribute value. The default is auto, which will write the value using the attribute’s existing type. Selecting another type will override the attribute’s existing type. For list attributes, the selected type override is applied to each list element. Available overrides are standard JSON types: bool float int json string
Key Name	(Optional) The key name used when writing the attribute. If left unset, the key name defaults to the attribute name. If the key name provided for an attribute conflicts with another key name in the object, the attribute name will be used instead of the specified key name.
Conflicting Key Strategy	Only applicable for Insert into Existing JSON Object mode. Specify how to handle cases where an attribute key already exists in the target JSON object: Keep Existing: Preserves the existing value. Overwrite: Replaces the existing value
Write Missing Attributes as Null	No (Default): Missing attributes are omitted. Yes: Missing attributes are written as null.

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

How to Set Parameter Values

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters.

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Date/Time Functions	Date and time functions are available in the Text Editor.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters	Create your own editable parameters.

Dialog Options - Tables

Table Tools

Transformers with table-style parameters have additional tools for populating and manipulating values.

Row Reordering

Enabled once you have clicked on a row item. Choices include:

Add a row
Remove a row
Move current row up one
Move current row down one
Move current row to top
Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

Cut a row - delete and copy to clipboard
Copy a row to the clipboard
Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

For more information, see Transformer Parameter Menu Options.

Reference

Processing Behavior	Feature-Based
Feature Holding	No
Dependencies	None
Aliases
History

FME Online Resources

The FME Community and Support Center Knowledge Base have a wealth of information, including active forums with 35,000+ members and thousands of articles.

Search for all results about the JSONObjectBuilder on the FME Community.

Examples may contain information licensed under the Open Government Licence – Vancouver, Open Government Licence - British Columbia, and/or Open Government Licence – Canada.