Added the following methods to AQConstraint in ADS-12.0.0, ADS-13.0.0, and trunk.

    /**
     * To check if this is a primary key constraint.
     *
     * @return
     *         true if this is a primary key constraint; false otherwise.
     */
    public boolean isPrimaryKeyConstraint();

    /**
     * To check if this is a foreign key constraint.
     *
     * @return
     *         true if this is a foreign key constraint; false otherwise.
     */
    public boolean isForeignKeyConstraint();

    /**
     * To check if this is a check constraint.
     *
     * @return
     *         true if this is a check constraint; false otherwise.
     */
    public boolean isCheckConstraint();

    /**
     * To check if this is a unique constraint.
     *
     * @return
     *         true if this is a unique constraint; false otherwise.
     */
    public boolean isUniqueConstraint();

    /**
     * To get the referenced column(s) for a foreign key constraint.
     *
     * @return
     *         An array of AQForeignKeyRefColumn objects if this is a foreign key constraint; empty array otherwise.
     */
    public AQForeignKeyRefColumn[] extractForeignKeyRefColumns();

    /**
     * To get the check condition for a check constraint.
     *
     * @return
     *         The check condition if this is a check constraint; null otherwise.
     */
    public String extractCheckCondition();

Sample code:

var table = conn.metadata.extractTable('SAMPLE', 'NORTHWIND', 'Order Details');
var constraints = table.extractConstraints();
for (var i = 0; i < constraints.length; i++)
{
   aqua.console.println("Constraint: " + constraints[i].getName());

   var columns = constraints[i].extractColumns();
   for (var j = 0; j < columns.length; j++)
   {
      aqua.console.println("Column: " + columns[j].getName());
   }

   if (constraints[i].isForeignKeyConstraint())
   {
      var refColumns = constraints[i].extractForeignKeyRefColumns();
      for (var r = 0; r < refColumns.length; r++)
      {
         aqua.console.println("Ref Column: " + refColumns[r].getDatabaseName() + "." +  refColumns[r].getSchemaName() + "." + refColumns[r].getTableName() + "." + refColumns[r].getName());
      }
   }

   if (constraints[i].isCheckConstraint())
   {
      aqua.console.println("Check Condition: " + constraints[i].extractCheckCondition());
   }
}