tWriteJSONField

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

Depending on the Talend solution you
are using, this component can be used in one, some or all of the following Job
frameworks:

Standard: see tWriteJSONField Standard properties.

The component in this framework is generally available.
MapReduce: see tWriteJSONField MapReduce properties.

The component in this framework is available only if you have subscribed to one
of the
Talend
solutions with Big Data.
Spark Batch:
see tWriteJSONField properties for Apache Spark Batch.

The component in this framework is available only if you have subscribed to one
of the
Talend
solutions with Big Data.
Spark Streaming:
see tWriteJSONField properties for Apache Spark Streaming.

The component in this framework is available only if you have subscribed to Talend Real-time Big Data Platform or Talend Data
Fabric.

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:

tWriteJSONField Standard properties

These properties are used to configure tWriteJSONField running in the Standard Job framework.

The Standard
tWriteJSONField component belongs to the Processing family.

The component in this framework is generally available.

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 (columns) to be processed and passed on to the next component. The schema is either Built-In or stored remotely in the Repository. 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 and store the schema locally for this component only. Related topic: see Talend Studio User Guide.
	Repository: You have already created the schema and stored it in the Repository. You can reuse it in various projects and Job designs. 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.

Global Variables

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.

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

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

Scenario: Writing flat data into JSON fields

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

Linking the components

Drop the following components from the Palette onto the design workspace: tFixedFlowInput, tWriteJSONField and tLogRow.
Link tFixedFlowInput and tWriteJSONField using a Row > Main connection.
Link tWriteJSONField and tLogRow using a Row > Main connection.

Configuring the components

Double-click tFixedFlowInput to display
its Basic settings view.
Click Edit schema to open the schema
editor.

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

Click OK to close the editor.
Select the Use Inline Content option and
enter the data below in the Content box:

Andrew;Wallace;Doc John;Smith;R&D Christian;Dior;Sales

1
2
3

Andrew;Wallace;Doc
John;Smith;R&D
Christian;Dior;Sales
Click tWriteJSONField to display its
Basic settings view.

Select the Remove root node option to
remove the root node setting from the JSON fields generated.
Click Configure JSON Tree to open the XML
tree editor.

The schema of tFixedFlowInput appears in
the Linker source panel.
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.
Right-click staff and select Add Sub-element from the context menu.
In the pop-up box, enter the sub-node name, namely firstname.

Repeat the steps to add two more sub-nodes, namely lastname and dept.
Right-click firstname and select
Set As Loop Element from the context
menu.
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.

Click OK to close the dialog box.

Repeat the steps to link the two other items.

Click OK to close the XML tree
editor.
Click Edit schema to open the schema
editor.
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.
Double-click tLogRow to display its
Basic settings view.

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

Executing the Job

Press Ctrl + S to save the Job.
Click F6 to execute the Job.

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

Related Scenarios

For related scenarios, see: