Available in Community Designer

Short Description
JSONExtract Attributes
Best Practices
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.

Component Data source Input ports Output ports Each to all outputs Different to different outputs Transformation Transf. req. Java CTL Auto-propagated metadata
JSONExtractJSON file0-11-n


Port typeNumberRequiredDescriptionMetadata
For port reading. See Reading from Input Port. One field (byte, cbyte, string).
For correct data recordsAny
1-n [2] For correct data recordsAny

[2] Other output ports are required if mapping requires that.


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

AttributeReqDescriptionPossible values
File URLyesAttribute 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. See XMLExtract Mapping Definition for more information. 
Mapping URL [1] Name of an external file, including its path which defines mapping of the input JSON structure to output ports. See XMLExtract Mapping Definition for more information. 
Equivalent XML Schema URL of a file that should be used for creating the Mapping definition. See JSONExtract Mapping Editor and XSD Schema for more information. 
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.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
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.


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 reads lists.


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 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.


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.


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

JSONExtract - mapping the list

Figure 55.12. JSONExtract - mapping the list

Best Practices

We recommend users to explicitly specify Charset.



JSONExtract is available since CloverETL 3.5.0-M2.


Since CloverETL 4.1.0-M1, you can map input fields to the output fields in this component.


Since CloverETL 4.1.0, you can read lists.

See also

Common Properties of Components
Specific Attribute Types
Common Properties of Readers
Readers Comparison