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The default folder for external .jar files in a local project is ./lib.

On a server, external .jar files can also be placed on the classpath of the application container.

You should add the .jar files to classpath. Open Project Properties dialog Project → Properties. Switch to Java Build Path → Libraries. Click Add JARs... and select the .jar files.

All .java and .class files should reside in shared sandbox.

If you click the Algorithm attribute value, dialog for editing of build-in java code opens. Use Switch to Java editor button to convert the transformation in Java to .java file. The file is opened as a new tab having java editor with syntax highlighting associated.

Transformation required by the component must extend org.jetel.component.AbstractGenericTransform class.

Following are the methods of the AbstractGenericTransform class:

One single record is represented by DataRecord class.

DataRecord record;

To create data record not connected to any particular port use static method newRecord() of DataRecordFactory. It requires record metadata.

String metadataId = getGraph().getDataRecordMetadataByName("recordName1");
DataRecordMetadata metadata = getGraph().getDataRecordMetadata(metadataId);
DataRecord record = DataRecordFactory.newRecord(metadata);

To read a record from input port use readRecordFromPort() function. Index of input port (starting from 0) is specified in parameter of the function.

record = readRecordFromPort(0);

The function returns null if no other records are available.

while ((record = readRecordFromPort(0)) != null) {
 	// Do something
}

To write a record to output port use writeRecordToPort() function. Parameters define index of output port and record to be written.

writeRecordToPort(0, record);

If you create a component with variable number of input or output ports, use

getComponent().getInputPortsMaxIndex()

or

getComponent().getOutputPortsMaxIndex()

to get maximal index of input or output ports.

Note that first input port has index 0. A component with N input ports has N-1 as a maximal index of input port.

Data field is represented by DataField class. You can get fields of data record using getFields() of DataRecord. You can get particular field using getField() taking field index or field name as a parameter.

DataRecord record;
DataField dataField1;
dataField1 = record.getField(0);
DataField dataField2;
dataField2 = record.getField("field2");

Use getValue() and setValue() methods of DataField to work with field values.

DataField field = record.getField(0);
String value = field.getValue();
field.setValue("some new value");

There are two classes necessary to work with metadata: DataRecordMetadata and DataFieldMetadata. Class DataRecordMetadata represents metadata of the whole record whereas DataFieldMetadata represents metadata of particular field.

Use getMetadata() method of DataRecord to get access to metadata of a record.

DataRecord record;
record = ...
DataRecordMetadata metadata = record.getMetadata();

Use getMetadata() method of DataField to get access to metadata of a field.

DataField dataField;
dataField = ...
DataFieldMetadata fieldMetadata = dataField.getMetadata();

To use metadata depending on its name use getDataRecordMetadataByName() to get metadata id and subsequently use getDataRecordMetadata() to get metadata corresponding to the id.

String metadataId = getGraph().getDataRecordMetadataByName("recordName1");
DataRecordMetadata metadata = getGraph().getDataRecordMetadata(metadataId);

To read value from dictionary use getValue() function, to write to from dictionary use setValue() function:

Dictionary dictionary = getGraph().getDictionary();
dictionary.setValue("mykey1", "NewValue");
String s = dictionary.getValue("mykey2");

Interface LookupTable gives you an access to lookup tables. Use put() to insert data record into an existing lookup table. Note that getLookupTable() requires lookup table ID. The parameter is not lookup table name!

LookupTable lookup = getGraph().getLookupTable("LookupTable0");
DataRecord record = ...;
lookup.put(record);

Use createLookup() to search for items matching the key.

LookupTable lt;
lt = ...

DataRecord patternRecord = DataRecordFactory.newRecord(lt.getMetadata());
patternRecord.getField(0).setValue("keyToBeSearchedPart1");
patternRecord.getField(2).setValue("keyToBeSearchedPart2");
String [] lookupFields = {"field1", "field3"};
RecordKey recordKey = new RecordKey(lookupFields, lt.getMetadata());
Lookup lookup;
lookup = lt.createLookup(recordKey, patternRecord);
lookup.seek();

while (lookup.hasNext()){
 	DataRecord record = lookup.next();
 	// process the result found
 	writeRecordToPort(0, record);
}

Graph parameters can be obtained from TransformationGraph using getGraphParameters(). To get particular parameter use getGraphParameter() with parameter name.

TransformationGraph graph = getGraph();
GraphParameters graphParameters = graph.getGraphParameters();
GraphParameter graphParameter = graphParameters.getGraphParameter("MY_PARAMETER");

Use getValue() or getValueResolved() to get parameter value.

String value = graphParameter.getValue();
String valueResolved = graphParameter.getValueResolved(RefResFlag.REGULAR);

You can get value of component attributes using getProperty() functions applied on TypedProperties.

String myStringValue = getProperties().getStringProperty("myCustomPropertyName1");

Integer myIntegerValue = getProperties().getIntProperty("myCustomPropertyName2");

Sequence is accessible from TransformationGraph via getSequence() function with sequence ID as a parameter.

Sequence seq = getGraph().getSequence("Sequence0");

Use nextValueInt(), nextValueLong() or nextValueString() to increment the sequence and return the incremented value. First call of any of the nextValue*() functions initializes the sequence to the initial sequence value and returns unincremented initial value.

String sequenceValue = seq.nextValueString();
int sequenceValueInt = seq.nextValueInt();
long sequenceValueLong = seq.nextValueLong();

To get last value returned by functions above use currentValueInt() currentValueLong() or currentValueString(). If none of the nextValue*() functions have been called before, current value is the start value of the sequence.

String sequenceValue = seq.currentValueString();
int sequenceValueInt = seq.currentValueInt();
long sequenceValueLong = seq.currentValueLong();

Database connections are accessible via getConnection() method of TransformationGraph. The method requires connection ID as a parameter.

getConnection() of DBConnection requires an identifier unique within the graph. You are suggested to use e.g. component ID.

IConnection connection = getGraph().getConnection("JDBC0");
if (connection instanceof DBConnection){
 	DBConnection dbconnection = (DBConnection) connection;
 	SqlConnection sqlconnection = dbconnection.getConnection("myUniqueID");
 	...
}

SqlConnection extends java.sql.Connection. See documentation on java.sql.Connection.

If you work with paths, use getFile() function to resolve the path correctly.

String param = getProperties().getStringProperty("InputFile");
File file = getFile(param);

You can access files via streams. Use getOutputStream() or getInputStream();

String param = getProperties().getStringProperty("InputFile");
InputStream is = getInputStream(param);

String param = getProperties().getStringProperty("OutputFile");
OutputStream os = getOutputStream(param, true);

Use log() function to log messages of important events of you Java-defined transformation.

getLogger().log(Level.INFO, "Some message" );

Create component removing empty directories.

Solution

Add new attribute Directory to the component.

Use the following code.

package jk;

import java.io.File;

import org.jetel.component.AbstractGenericTransform;

/**
 * This is an example custom component. It shows how you can remove empty
 * directories.
 */
public class CustomJavaComponentExample01 extends AbstractGenericTransform {

	private void removeEmptyDirectories(File dir) {
		if (!dir.isDirectory() || !dir.canRead() || !dir.canWrite()) {
			return;
		}

		for (File f : dir.listFiles()) {
			if (f.isDirectory()) {
				removeEmptyDirectories(f);
				if (f.listFiles().length == 0) {
					f.delete();
				}
			}
		}
	}

	@Override
	public void execute() {
		String directory = getProperties().getStringProperty("Directory");
		File dir = getFile(directory);
		removeEmptyDirectories(dir);
	}

}

A component has to have one input port and one output port connected. Each port should have metadata assigned. The component has attribute Multiplier having integral value.

Solution

Use checkConfig() function of a component's template.

@Override
public ConfigurationStatus checkConfig(ConfigurationStatus status) {
 	super.checkConfig(status);
	 	
 	if (getComponent().getInPorts().size() != 1 || getComponent().getOutPorts().size() != 1) {
 	 	status.add("One input and one output port must be connected!", Severity.ERROR, getComponent(), Priority.NORMAL);
 	 	return status;
 	}
	 	
 	DataRecordMetadata inMetadata = getComponent().getInputPort(0).getMetadata();
 	DataRecordMetadata outMetadata = getComponent().getOutputPort(0).getMetadata();
 	if (inMetadata == null || outMetadata == null) {
 	 	status.add("Metadata on input or output port not specified!", Severity.ERROR, getComponent(), Priority.NORMAL);
 	}
	 	
 	if (!getProperties().containsKey("Multiplier")) {
 		status.add("Multiplier property is missing or is not set.", Severity.ERROR, getComponent(), Priority.NORMAL, "Multiplier");
 		return status;
 	}

 	try {
 		Integer.parseInt(getProperties().getStringProperty("Multiplier"));
	} catch(Exception e){
 	 	status.add("Multiplier is not integer!", Severity.ERROR, getComponent(), Priority.NORMAL, "Multiplier");
 	}

	 return status;
}