CustomJavaWriter
Short Description
CustomJavaWriter executes a user-defined Java code.
Component | Same input metadata | Sorted inputs | Inputs | Outputs | Each to all outputs | Java | CTL | Auto-propagated metadata |
---|---|---|---|---|---|---|---|---|
CustomJavaWriter |
- |
- |
0-n |
0-n |
- |
✓ |
⨯ |
⨯ |
Ports
The number of ports depends on the Java code.
Metadata
By default, CustomJavaWriter does not propagate metadata. Metadata propagation can be configured using the Metadata propagation algorithm and Metadata propagation algorithm class attributes.
CustomJavaWriter has no metadata templates.
Requirements on metadata depend on a user-defined transformation.
CustomJavaWriter Attributes
Attribute | Req | Description | Possible values |
---|---|---|---|
Basic |
|||
Algorithm |
A runnable transformation in Java defined in the graph. |
||
Algorithm URL |
A URL to an external file defining a runnable transformation in Java. |
||
Algorithm class |
An external runnable transformation class. |
||
Advanced |
|||
An algorithm for metadata propagation written in Java. |
|||
An external metadata propagation class. |
|||
Algorithm source charset |
The encoding of the external file defining the transformation. The default encoding depends on DEFAULT_SOURCE_CODE_CHARSET in defaultProperties. |
UTF-8 |
Details
CustomJavaWriter executes the Java transformation. CustomJavaWriter is a more specific CustomJavaComponent focused on writing data.
There are other similar Java components: CustomJavaReader, CustomJavaTransformer and CustomJavaComponent. All these components use a transformation defined in Java, they differ in templates being used.
You can use Public CloverDX API in this component. General parts of custom Java components and Public CloverDX API are described in CustomJavaComponent.
Java Interfaces for CustomJavaWriter
A transformation required by the component must extend the org.jetel.component.AbstractGenericTransform
class.
The component has the same Java interface as CustomJavaComponent, but it provides a different Java template. See Java Interfaces for CustomJavaComponent.
Custom Metadata Propagation for CustomJavaWriter
CustomJavaWriter can propagate metadata using a custom algorithm.
Metadata propagation algorithm must extend the org.jetel.component.GenericMetadataProvider
class.
The component has the same Java interface as CustomJavaComponent, see Custom Metadata Propagation for CustomJavaComponent.
Examples
Writing Maps and Lists
Create a component capable of writing all input metadata fields as strings. Input metadata fields can include maps and lists.
Solution
package jk;
import java.io.IOException;
import java.io.OutputStream;
import org.jetel.component.AbstractGenericTransform;
import org.jetel.data.DataField;
import org.jetel.data.DataRecord;
import org.jetel.exception.JetelRuntimeException;
/**
* This is an example custom writer. It shows how you can write string
* representations of fields into file.
*/
public class CustomJavaWriterExample01 extends AbstractGenericTransform {
@Override
public void execute() {
String fileUrl = getProperties().getStringProperty("FileUrl");
DataRecord record;
try (OutputStream os = getOutputStream(fileUrl, false)) {
while ((record = readRecordFromPort(0)) != null) {
StringBuffer sb = new StringBuffer();
DataField[] dataFields = record.getFields();
int fieldCount = 1;
for (DataField df : dataFields) {
sb.append(df.getValue() != null ? df.getValue().toString() : "");
if (df.getMetadata().getDelimiter() != null) {
sb.append(df.getMetadata().getDelimiter());
} else {
if (fieldCount != dataFields.length) {
sb.append(record.getMetadata().getFieldDelimiter());
}
}
++fieldCount;
}
sb.append(record.getMetadata().getRecordDelimiter());
os.write(sb.toString().getBytes("UTF-8"));
}
} catch (IOException e) {
throw new JetelRuntimeException(e);
}
}
}
Best Practices
If Algorithm URL is used, we recommend to explicitly specify Charset.
Compatibility
Version | Compatibility Notice |
---|---|
4.1.0-M1 |
CustomJavaWriter is available since 4.1.0-M1. |
5.3.0 |
CustomJavaWriter can now propagate metadata - added new attributes Metadata propagation algorithm and Metadata propagation algorithm class. |