Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/SortKeyHandle.java
public void setDirection( String direction ) throws SemanticException
	{
		setProperty( SortKey.DIRECTION_MEMBER, direction );
	}
	/**
	 * Returns the name of the column that needs sort.
	 * 
	 * @return the column name
	 * 
	 * @deprecated This property has been removed. See the method
	 *             {@link #getKey()}.
	 */
	public String getColumnName( )
	{
		return getKey( );
	}
	/**
	 * Sets the name of the column that needs sort.
	 * 
	 * @param columnName
	 *            the column name to set
	 * 
	 * @deprecated This property has been removed. See the method
	 *             {@link #setKey(String)}.
	 */
	public void setColumnName( String columnName )
	{
		setKey( columnName );
	}
}