Writing JavaScript Filters

The JavaScript interface to the replicator enables filters to be written using standard JavaScript with a complete object-based interface to the internal Java objects and classes that make up the THL data.

For more information on the Rhino JavaScript implementation, see "Rhino"

The basic structure of a JavaScript filter is as follows:

// Prepare the filter and setup structures

prepare()
{

}

// Perform the filter process; function is called for each event in the THL

filter(event)
{

// Get the array of DBMSData objects
  data = event.getData();

  // Iterate over the individual DBMSData objects
  for(i=0;i<data.size();i++)
  {
    // Get a single DBMSData object
    d = data.get(i);

    // Process a Statement Event; event type is identified by comparing the object class type

    if (d = instanceof com.continuent.tungsten.replicator.dbms.StatementData)
    {
      // Do statement processing
    }
    else if (d = instanceof com.continuent.tungsten.replicator.dbms.RowChangeData)
    {
      // Get an array of all the row changes
      rows = data.get(i).getRowChanges();

      // Iterate over row changes
      for(j=0;j<rows.size();j++)
      {
        // Get the single row change
        rowchange = rows.get(j);

        // Identify the row change type
        if (rowchange.getAction() == "INSERT")
        {
        }
        ....

    }
  }
}
}

The following sections will examine the different data structures, functions, and information available when processing these individual events.