Use CustomJavaReader to create a new user-defined component.

Add a new custom attribute RecordCount to the component and set up a value to the attribute, e.g. to 5.

Define the transformation.

package jk;

import java.security.SecureRandom;
import org.jetel.component.AbstractGenericTransform;
import org.jetel.data.DataRecord;

/**
 * This is an example custom reader. It shows how you can create records using a
 * data source.
 */
public class CustomJavaReaderExample01 extends AbstractGenericTransform {

    @Override
    public void execute() {
        Integer recordCount = getProperties().getIntProperty("RecordCount");

        // Output record prepared for writing to output port 0.
        DataRecord record = outRecords[0];

        SecureRandom secureRandom = new SecureRandom();

        for (int i = 0; i < recordCount; ++i) {
            byte[] b = new byte[32];

            secureRandom.nextBytes(b);
            record.getField("field1").setValue(b);
            writeRecordToPort(0, record);
            record.reset();
        }
    }
}

Metadata on the output port must have one field named field1. The field has the byte data type.

Add the FileUrl attribute to the component.

package jk;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import org.jetel.component.AbstractGenericTransform;
import org.jetel.data.DataRecord;
import org.jetel.exception.JetelRuntimeException;

/**
 * This is an example custom reader. It shows how you can read data from file
 * with specific format.
 */
public class CustomJavaReaderExample02 extends AbstractGenericTransform {

    @Override
    public void execute() {
        DataRecord record = outRecords[0];
        String fileUrl = getProperties().getStringProperty("FileUrl");
        File file = getFile(fileUrl);

        try (FileInputStream inputStream = new FileInputStream(file)) {
            for (int length = inputStream.read(); length > 0; length = inputStream.read()) {
                byte[] b = new byte[length];
                inputStream.read(b, 0, length);

                record.getField("field1").setValue(length);
                record.getField("field2").setValue(>b);
                writeRecordToPort(0, record);
                record.reset();
            }
        } catch (IOException e) {
            throw new JetelRuntimeException(e);
        }
    }
}

Note: input data is in binary format. The first header contains a character ! which corresponds to the value 33. Thirty-three characters follow. The header of the second record has the value 34 which is displayed as a character ". Thirty-four bytes follow.

Metadata on the output port must have two fields named field1 and field2 with the types integer and byte.