Right up front let's make it clear that you should not use this method for performing type conversion

This method is meant to massage existing data into a state that can be converted.

Right up front let's make it clear that you should not use this method for performing type conversion

Just like @see #preProcessPopulate the preProcessUpdate method is meant to massage data into a state that can be converted.

Example from JComboBoxComponentHandler

 public class JComboBoxComponentHandler
 extends AbstractComponentHandler
 implements ComponentHandler
 {
 ...
 protected String getSetterName() {
 if (compareProperties != null && compareProperties.length > 0) {
 return "setSelectedIndex";
 } else {
 return "setSelectedItem";
 }
 ...
 }
 

 public class JLabelComponentHandler extends TextComponentHandler {
 public boolean getDefaultReadOnly() {
 return true;
 }
 }
 

Example from JListComponentHandler:

 public class JListComponentHandler
 extends AbstractComponentHandler
 implements ComponentHandler {
 ...
 public boolean isPopulateHandleable(JList component, Object modelPropertyValue) {
 return modelPropertyValue != null;
 }
 ...
 }
 

Right up front let's make it clear that you should not use this method for performing type conversion

This method is meant to massage existing data into a state that can be converted. Let's take a look at the TextComponentHandler. You can see that the TextComponentHandler examines if the modelPropertyValue is null and if it is alters it's representation to an empty String. The reason for this is that JTextField will display a null as 'null' and that is undesireable. It would not be appropriate to deal with this in a TypeHandler. For a more complex example you can take a look at the @see JComboBoxComponentHandler#preProcessPopulate which is a very involved implementation.

TextComponent Handler Example

 public class TextComponentHandler
 extends AbstractComponentHandler
 implements ComponentHandler
 {
 ...
 public Object preProcessPopulate(JComponent component, Object modelPropertyValue) {
 return modelPropertyValue == null ? "" : modelPropertyValue;
 }
 ...
 }
 

Right up front let's make it clear that you should not use this method for performing type conversion

Just like @see #preProcessPopulate the preProcessUpdate method is meant to massage data into a state that can be converted.

 public class JListComponentHandler
 extends AbstractComponentHandler
 implements ComponentHandler {
 ...
 public Object preProcessUpdate(JList component, Object formFieldValue) {
 // if a single selection return a single object
 if (component.getSelectionMode() == ListSelectionModel.SINGLE_SELECTION) {
 Object[] selectedValues = (Object[]) formFieldValue;
 if (selectedValues.length == 0) {
 return null;
 } else {
 return selectedValues[0];
 }
 } else {
 //otherwise return an array
 return formFieldValue;
 }
 }
 ...
 }