Version

    JSONExtract

    JSONExtract 64x64

    Short Description

    Ports

    Metadata

    JSONExtract Attributes

    Details

    Examples

    Best Practices

    Compatibility

    See also

    Short Description

    JSONExtract reads data from JSON files using SAX technology. It can also read data from compressed files, input port, and dictionary.

    Data source Input ports Output ports Each to all outputs Different to different outputs Transformation Transf. req. Java CTL Auto-propagated metadata

    JSON file

    0-1

    1-n

    Ports

    Port type Number Required Description Metadata

    Input

    0

    For port reading. See Reading from Input Port.

    One field (byte, cbyte, string).

    Output

    0

    For correct data records

    Any

    1-n

    [1]

    For correct data records

    Any

    1

    Other output ports are required if mapping requires that.

    Metadata

    JSONExtract does not propagate metadata.

    JSONExtract has no metadata template.

    Metadata on optional input port must contain string or byte or cbyte field.

    Metadata on each output port does not need to be the same.

    Each metadata can use Autofilling Functions.

    JSONExtract Attributes

    Attribute Req Description Possible values

    Basic

    File URL

    yes

    Attribute specifying what data source(s) will be read (JSON file, input port, dictionary). See Supported File URL Formats for Readers.

    Charset

    Encoding of records which are read.

    any encoding, default system one by default

    Mapping

    [1]

    Mapping of the input JSON structure to output ports. For more information, see XMLExtract Mapping Definition.

    Mapping URL

    [1]

    Name of an external file, including its path which defines mapping of the input JSON structure to output ports. For more information, see XMLExtract Mapping Definition.

    Equivalent XML Schema

    URL of a file that should be used for creating the Mapping definition. For more information, see JSONExtract Mapping Editor and XSD Schema.

    Use nested nodes

    By default, nested elements are also mapped to output ports automatically. If set to false, an explicit <Mapping> tag must be created for each such nested element. See Use nested nodes examples.

    true (default) | false

    Trim strings

    By default, white spaces from the beginning and the end of the elements values are removed. If set to false, they are not removed.

    true (default) | false

    Advanced

    Number of skipped mappings

    Number of mappings to be skipped continuously throughout all source files. See Selecting Input Records.

    0-N

    Max number of rows to output

    Maximum number of records to be read continuously throughout all source files. See Selecting Input Records.

    0-N

    1

    One of these must be specified. If both are specified, Mapping URL has higher priority.

    Details

    JSONExtract reads data from JSON files using SAX technology. This component is faster than JSONReader which can read JSON files too. JSONExtract does not use DOM, so it uses less memory than JSONReader.

    JSONExtract can read lists.

    JSONExtract can convert JSON to variant. Result variant can contain field/array values of following data types - null, string, boolean, long and number.

    JSONExtract is very similar to XMLExtract. JSONExtract internally transforms JSON to XML and uses XMLExtract to parsing the data. Therefore, you can generate xsd file for corresponding xml file.

    Mapping in JSONExtract is almost same as in XMLExtract. The main difference is, that JSON does not have attributes. For more information, see XMLExtract’s Details.

    JSONExtract Mapping Editor and XSD Schema

    JSONExtract Mapping Editor serves to set up mapping from JSON tree structure to one ore more output ports without the necessity of being aware how to create mapping of field using an XML editor.

    To be able to use the editor, the editor needs to have created equivalent xsd schema. The equivalent xsd schema is created automatically. Only the directory for the schema needs to be specified.

    Any other operations to set up mapping are described in above mentioned XMLExtract.

    Mapping Input Fields to the Output Fields

    In JSONExtract, you can map input fields to the output in the same way as you map JSON fields. The input field mapping works in all three processing modes.

    Examples

    Use nested nodes examples

    It is important to bear in mind that when the Use nested nodes attribute is set to True, one should be careful if there are elements with the same name because the JSONExtract component might return a different value than expected. See the following examples for further explanation:

    In this sample JSON file there are two elements called id: the first one is a nested element within the groups element, and the other one is nested within the main result element. The value of the first id is groupID, and the value of the other id is resultID.

    {
        "root": {
          "result": {
            "groups": {
              "id": "groupID"
            },
            "isEnabled": true,
            "isMetric": true,
            "id": "resultID",
            "language": "en",
            "firstDayOfWeek": "Sunday",
            "name": "North America"
          }
        }
      }
    JSONExtract example nested elements json file
    Figure 363. JSON structure and values

    Example 1: The mapping is at the level of the main result element, and the Automap elements or attributes to fields with same name option is turned on, or the id (resultID) is specifically mapped.

    JSONExtract example1 nested nodes mapping
    Figure 364. Mapping 1

    The value of the id element will differ based on if the Use nested nodes value is set to True or False:

    • When the Use nested nodes value is set to True, the returned record is groupID. This is because it is the first id element that is found when parsing the data.

    • When the Use nested nodes value is set to False, the returned record is resultID. In this case, the groups id element is ignored, and the first found id element is the one within the result element.

    Example 2: The mapping is at the id element nested within the result element.

    JSONExtract example2 nested nodes mapping
    Figure 365. Mapping 2

    The returned values of the id element will again differ based on if the Use nested nodes value is set to True or False:

    • When the Use nested nodes value is set to True, there are two returned records: groupID and resultID.

    • When the Use nested nodes value is set to False, only the resultID record is returned.

    Reading lists

    JSON file contains information about employees and orders. Each item contains employee ID and list of order IDs.

    {
      "jsonextract_order" : {
        "employee" : "Henri",
        "orders" : [ "order01", "order08", "order15" ]
      },
      "jsonextract_order" : {
        "employee" : "Jane",
        "orders" : [ "order02", "order05", "order09" ]
      }
    }

    Read data for further processing.

    Solution

    Use the File URL attribute to point to the source file and the Mapping attribute to define mapping.

    JSONExtract example 01
    Figure 366. JSONExtract - mapping the list
    Reading variants

    JSON file contains information about employees and orders. Each item contains employee ID and list of order IDs.

    {
      "jsonextract_order" : {
        "employee" : "Henri",
        "orders" : [ "order01", "order08", "order15" ]
      },
      "jsonextract_order" : {
        "employee" : "Jane",
        "orders" : [ "order02", "order05", "order09" ]
      }
    }

    Read data for further processing.

    Solution

    Use the File URL attribute to point to the source file and the Mapping attribute to define mapping.

    JSONExtract example 02
    Figure 367. JSONExtract - mapping the variant

    Content of mapped output variant field depends on structure of input JSON.

    // for the first input element
    $out.0.employeeData["jsonextract_order"]["employee"]; // contains 'Henri'
    $out.0.employeeData["jsonextract_order"]["orders"][0]; // contains 'order01'

    Best Practices

    We recommend users to explicitly specify Charset.

    Compatibility

    Version Compatibility Notice

    3.5.0-M2

    JSONExtract is available since 3.5.0-M2.

    4.1.0-M1

    You can now map input fields to the output fields in this component.

    4.1.0

    You can now read lists.

    5.11.0

    You can now extract JSON to variant.

    5.11.0

    Null values are no longer converted to an empty string on output.