August 17, 2023

tWriteJSONField – Docs for ESB 5.x

tWriteJSONField

tWriteJSONField_icon32_white.png

tWriteJSONField properties

Component family

Processing/Fields

 

Function

tWriteJSONField transforms the
incoming data into JSON fields.

If you have subscribed to one of the Talend solutions with Big Data, you are
able to use this component in a Talend Map/Reduce Job to generate
Map/Reduce code. In that situation, tWriteJSONField belongs to the MapReduce component
family.

Purpose

tWriteJSONField transforms the
incoming data into JSON fields and transfers them to a file, a
database table, etc.

Basic settings

Output Column

List of the columns defined in the output schema to hold the JSON
field generated.

 

Configure JSON Tree

Opens the interface to create the JSON data structure. For more
information, see Configuring a JSON Tree.

 

Schema and Edit
Schema

A schema is a row description, it defines the number of fields to
be processed and passed on to the next component. The schema is
either Built-in or stored remotely
in the Repository.

Since version 5.6, both the Built-In mode and the Repository mode are
available in any of the Talend solutions.

Click Edit schema to make changes to the schema. If the
current schema is of the Repository type, three options are
available:

  • View schema: choose this option to view the
    schema only.

  • Change to built-in property: choose this option
    to change the schema to Built-in for local
    changes.

  • Update repository connection: choose this option to change
    the schema stored in the repository and decide whether to propagate the changes to
    all the Jobs upon completion. If you just want to propagate the changes to the
    current Job, you can select No upon completion and
    choose this schema metadata again in the [Repository
    Content]
    window.

 

 

Built-in: You create the schema
and store it locally for this component only. Related topic: see
Talend Studio User
Guide
.

 

 

Repository: The schema already
exists and is stored in the Repository, hence can be reused in
various projects and Job flowcharts. Related topic: see Talend Studio User
Guide
.

 

Sync columns

Click to synchronize the output file schema with the input file
schema. The Sync function only displays once the Row connection is
linked with the output component.

 

Group by

Define the aggregation set, the columns you want to use to regroup
the data.

Warning

Make sure that the data to be grouped is in sequential
order.

 

Remove root node

Select this check box to remove the root node from the JSON field
generated.

Advanced settings

 

tStatCatcher Statistics

Select this check box to gather the Job processing metadata at a
Job level as well as at each component level. Note that this check box is not available in
the Map/Reduce version of the component.

Global Variables

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

NB_LINE: the number of rows read by an input component or
transferred to an output component. This is an After variable and it returns an
integer.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
Space
to access the variable list and choose the variable to use from it.

For further information about variables, see Talend Studio
User Guide.

Usage

Preceded by an input component, this component wraps the incoming
data into a JSON field.

Usage in Map/Reduce Jobs

If you have subscribed to one of the Talend solutions with Big Data, you can also
use this component as a Map/Reduce component. In a Talend Map/Reduce Job, this
component is used as an intermediate step and other components used along with it must be
Map/Reduce components, too. They generate native Map/Reduce code that can be executed
directly in Hadoop.

You need to use the Hadoop Configuration tab in the
Run view to define the connection to a given Hadoop
distribution for the whole Job.

For further information about a Talend Map/Reduce Job, see the sections
describing how to create, convert and configure a Talend Map/Reduce Job of the
Talend Big Data Getting Started Guide.

Note that in this documentation, unless otherwise explicitly stated, a scenario presents
only Standard Jobs, that is to say traditional Talend data
integration Jobs, and non Map/Reduce Jobs.

Configuring a JSON Tree

When configuring a JSON tree, the default type of an element is string. If an
element is not of type string, you need to add an
attribute for the element to set its type.

  • For an integer, double, float, or
    boolean element, you need to add an
    attribute named type and set its static
    value to integer, number, float, or boolean respectively.

  • For an array element, you need to add
    an attribute named class and set its static
    value to array, and then add a sub-element
    named element set as a loop.

  • For an object element, you need to add
    an attribute named class and set its static
    value to object.

The following figure shows an example of JSON tree configuration:

components-twritejsonfield_configurejsontree.png

Scenario: Writing flat data into JSON fields

In this scenario, flat data is wrapped into JSON fields via tWriteJSONField.

Linking the components

  1. Drop the following components from the Palette onto the design workspace: tFixedFlowInput, tWriteJSONField and tLogRow.

  2. Link tFixedFlowInput and tWriteJSONField using a Row > Main connection.

  3. Link tWriteJSONField and tLogRow using a Row > Main connection.

    use_case_twritejsonfield_1.png

Configuring the components

  1. Double-click tFixedFlowInput to display
    its Basic settings view.

    use_case_twritejsonfield_2.png
  2. Click Edit schema to open the schema
    editor.

    use_case_twritejsonfield_3.png

    Click the [+] button to add three
    columns, namely firstname, lastname and dept, with the type of string.

    Click OK to close the editor.

  3. Select the Use Inline Content option and
    enter the data below in the Content box:

  4. Click tWriteJSONField to display its
    Basic settings view.

    use_case_twritejsonfield_4.png

    Select the Remove root node option to
    remove the root node setting from the JSON fields generated.

  5. Click Configure JSON Tree to open the XML
    tree editor.

    use_case_twritejsonfield_5.png

    The schema of tFixedFlowInput appears in
    the Linker source panel.

  6. In the Linker target panel, click the
    default rootTag and type in staff, which is the root node of the JSON field
    to be generated.

  7. Right-click staff and select Add Sub-element from the context menu.

  8. In the pop-up box, enter the sub-node name, namely firstname.

    use_case_twritejsonfield_6.png

    Repeat the steps to add two more sub-nodes, namely lastname and dept.

  9. Right-click firstname and select
    Set As Loop Element from the context
    menu.

  10. Drop firstname from the Linker source panel to its counterpart in the
    Linker target panel.

    In the pop-up dialog box, select Add linker to
    target node
    .

    use_case_twritejsonfield_7.png

    Click OK to close the dialog box.

    Repeat the steps to link the two other items.

    Click OK to close the XML tree
    editor.

  11. Click Edit schema to open the schema
    editor.

    use_case_twritejsonfield_8.png
  12. Click the [+] button in the right panel
    to add one column, namely staff, which
    will hold the JSON data generated.

    Click OK to close the editor.

  13. Double-click tLogRow to display its
    Basic settings view.

    use_case_twritejsonfield_9.png

    Select Table (print values in cells of a
    table)
    for a better display of the results.

Executing the Job

  1. Press Ctrl + S to save the Job.

  2. Click F6 to execute the Job.

    use_case_twritejsonfield_10.png

    As shown above, the JSON fields have been generated correctly, with the
    root node settings removed.


Document get from Talend https://help.talend.com
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