Partitioner is the main Java interface that a plugin implements.
Keep Track of Partitioner Settings
The implementing class keeps track of partitioner settings using private fields with corresponding
set methods. The
dialog class implementing
PartionerDialogInterface is using these methods to copy the user supplied configuration in and out of the dialog.
public Object clone()
This method is called when a step containing partitioning configuration is duplicated in Spoon. It needs to return a deep copy of this partitioner object. It is essential that the implementing class creates proper deep copies if the configuration is stored in modifiable objects, such as lists or custom helper objects. The copy is created by calling
super.clone() and deep-copying any fields the partitioner may have declared.
public Partitioner getInstance()
This method is required to return a new instance of the partitioner class, with the plugin id and plugin description inherited from the instance upon which this method is called.
Serialize Partitioner Settings
The plugin serializes its settings to both XML and a PDI repository.
public String getXML()
This method is called by PDI whenever the plugin needs to serialize its settings to XML. It is called when saving a transformation in Spoon. The method returns an XML string containing the serialized settings. The string contains a series of XML tags, one tag per setting. The helper class
org.pentaho.di.core.xml.XMLHandler constructs the XML string.
public void loadXML()
This method is called by PDI whenever a plugin reads its settings from XML. The XML node containing the plugin settings is passed in as an argument. Again, the helper class
org.pentaho.di.core.xml.XMLHandler is used to read the settings from the XML node.
public void saveRep()
This method is called by PDI whenever a plugin saves its settings to a PDI repository. The repository object passed in as the first argument provides a convenient set of methods for serializing settings. The transformation id and step id passed in are used as identifiers when calling the repository serialization methods.
public void readRep()
This method is called by PDI whenever a plugin needs to read its configuration from a PDI repository. The step id given in the arguments should be used as the identifier when using the repositories serialization methods.
When developing plugins, make sure the serialization code is in synch with the settings available from the partitioner plugin dialog. When testing a partitioned step in Spoon, PDI internally saves and loads a copy of the transformation before it is executed.
Provide the Name of the Dialog Class
PDI needs to know which class will take care of the settings dialog for the plugin. The interface method
getDialogClassName() must return the name of the class implementing the
StepDialogInterface for the partitioner.
Partition Incoming Rows During Runtime
The class implementing
Partitioner executes the actual logic that distributes the rows to available partitions.
public int getPartition()
This method is called with the row structure and the actual row as arguments. It returns the partition to which this row is sent. The total number of partitions is available in the inherited field
nrPartitions and the return value is between zero (0, inclusive) and
Interface with the PDI plugin system
In order for PDI to recognize the plugin, the class implementing the
Partitioner interface must also be annotated with the Java annotation
Supply these annotation attributes:
| ||A globally unique ID for the plugin|
| ||A short label for the plugin|
| ||A longer description for the plugin|
| ||If the |