tWriteDynamicFields

tWriteDynamicFields properties

Component family	Processing/Fields
Function	tWriteDynamicFields creates an output dynamic column from input columns.
Purpose	tWriteDynamicFields allows you to create a dynamic schema from input columns in the component.
Basic settings	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. Click Sync columns to retrieve the schema from the previous component in the Job.
		Built-in: You create the schema and store it locally for the relevant component. 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 flowcharts. Related topic: see Talend Studio User Guide.
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	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	This component handles flow of data therefore it requires input and output components.
Log4j	The activity of this component can be logged using the log4j feature. For more information on this feature, see Talend Studio User Guide. For more information on the log4j logging levels, see the Apache documentation at http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Level.html.
Limitation	n/a

Scenario 1: Create a dynamic column and extract its content

This Java scenario contains five components. It aims at creating a Dynamic
type column from a schema and extracting the columns contained in this
dynamic column. These transformation results are displayed into the
console.

Linking the components

From the Palette to
the design workspace, drag and drop the following
components:

– a tRowGenerator to
generate a flow containing customer information,

– a tWriteDynamicFields to replace columns
with a Dynamic column,

– two tLogRow to
display the results into the console,

– a tExtractDynamicFields to extract
content from the dynamic column.
Connect tRowGenerator
to tWriteDynamicFields using a Row > Main link.
Connect tWriteDynamicFields to the first
tLogRow using a
Row >
Main link.
Connect tLogRow to
tExtractDynamicFields using a
Row >
Main link.
Connect tExtractDynamicFields to the second
tLogRow using a
Row >
Main link.
Rename both tLogRow
by double-clicking them.

Type in their new name,
dynamicColumn and
standard column
respectively.

Configuring the components

In the design workspace, double-click the tRowGenerator to open its
editor.
Click seven times on the [+] button to add seven columns to the
schema. Name them id,
firstName,
lastName,
street,
city,
States and
otherData,
respectively.
In the Type column,
select Integer for
id and String for all other fields.

In the Functions
columns, select the function you want to
apply to each column in the schema.

Click OK to validate
the configuration and close the editor.

A pop-up window opens and asks you to propagate the
changes. Click Yes.
In the design workspace, double-click tWriteDynamicFields
component to display its Basic
settings view.

Click the […]
button next to Edit
schema to set the schema of the
component.
In the schema editor, click on
otherData column, then click to add the column on the output
side.

This way, the column will be displayed in the output,
but it will not be included into the dynamic
column.
Click the [+] button
in the output area to add a column.

Name it columnDynamic and set
its Type to
Dynamic.

Warning

The dynamic column must be defined
in the last row of the schema.

Warning

The column names must be exactly the
same on both sides of the editor, otherwise the
output columns will not be
recognised.
Click OK to validate
your changes and close the editor.

Warning

The dynamic schema
feature is only supported in Built-In mode.

All columns that are not in the output area in the
editor will be included into the dynamic
column.
In the design workspace, double-click the first
tLogRow to
display its Basic
settings view.

In the Mode area,
select the Table (print value
in cells of a table) option.
In the design workspace, double-click tWriteDynamicFields
component to display ots Basic
settings view.

Click the […]
button next to Edit
schema.
Select in the left area the columns you want to add to
the tExtractDynamicFields schema and click
the button to copy them.

Click OK to close the
editor.
In the design workspace, double-click the tExtractDynamicFields
component to display its Basic
settings view.

Click the […]
button next to Edit
schema.

In the schema editor, click the button in the output area to
paste the columns copied from tWriteDynamicFields component.

In the input area, click the Dynamic column and click
the button to add the dynamic
column to the output schema.

Click OK to validate
your changes and close the editor.
In the design workspace, double-click the second
tLogRow to
display its Basic
settings view.
In the Mode area,
select Table (print value in
cells of a table) option.

Executing the Job

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

The first tLogRow
component displays in the console the dynamic column
in addition to the otherData
column you have already defined in the output schema
of the tWriteDynamicFields component.

The second tLogRow
displays in the console all the extracted columns
(id,
firstName and
lastName) from the dynamic
one, the otherData column that
has not been included into the dynamic column and
the dynamic column which still contains all columns
voluntarily not extracted.

Scenario 2: Extracting the contents of a dynamic column via tJavaRow

In this scenario, a dynamic column is created via tWriteDynamicFields and its contents are then extracted
by the customized code in tJavaRow.

Linking the components

Drop tFixedFlowInput,
tWriteDynamicFields, tLogRow and tJavaRow onto the
workspace.
Link tFixedFlowInput
to tWriteDynamicFields using the
Row > Main connection.
Link tWriteDynamicFields to tLogRow using the Row > Main connection.
Link tLogRow to
tJavaRow using
the Row > Main connection.

Configuring the components

Double-click tFixedFlowInput to open its Basic settings view.
Select Use Inline Content
(delimited file) in the Mode area.
In the Content field,
enter the data to pass to tWriteDynamicFields, for
example:

1;Andy;Doc 2;Anderson;Dev

1
2

1;Andy;Doc
2;Anderson;Dev
Click the Edit schema
button to open the schema editor.
Click the [+] button
to add three columns, namely id, name, and dept, of the Integer and String types
respectively.
Click OK to validate
the setup and close the editor.
Double-click tWriteDynamicFields to open its
Basic settings
view.
Click the Edit schema
button to open the schema editor.
Click the [+] button
in the right panel to add two columns, namely
id and
dynamic, of the
Integer and Dynamic types respectively.

The column id
contains the value of the column id from tFixedFlowInput and the
column dynamic
contains the values of the columns name and dept from tFixedFlowInput.
Click OK to validate
the setup and close the editor.
Double-click tLogRow
to open its Basic
settings view.

Select Table (print values in
cells of a table) for a better display
of the results.
Double-click tJavaRow
to open its Basic
settings view.

In the Code field,
enter the Java code to extract the contents of the
dynamic column dynamic:

Dynamic columns = row3.dynamic;
 
for (int i = 0; i &lt; columns.getColumnCount(); i++) {  
    DynamicMetadata columnMetadata = columns.getColumnMetadata(i);  
    System.out.println(columnMetadata.getName() + ": " + 
columns.getColumnValue(i) + "; " + columnMetadata.getType());
}

Dynamic columns = row3.dynamic;

for (int i = 0; i < columns.getColumnCount(); i++) {

DynamicMetadata columnMetadata = columns.getColumnMetadata(i);

System.out.println(columnMetadata.getName() + ": " +

columns.getColumnValue(i) + "; " + columnMetadata.getType());

}

The dynamic column dynamic of the flow row3 is specified for
retrieving the names, values and types of columns
that it contains.

Executing the Job

Press Ctrl+S to save
the Job.
Press F6 to run the
Job.

As shown above, the columns contained in the dynamic
column have been correctly extracted.

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

Thank you for watching.

Docs 5.x

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tWriteDynamicFields – Docs for ESB 5.x