public class SelectItemsConverter extends Object implements Converter
The omnifaces.SelectItemsConverter allows you to populate a selection component with complex Java
model objects (entities) as value of <f:selectItems> and have JSF convert those
automatically back without the need to provide a custom converter which may need to do the job based on
possibly expensive service/DAO operations. This converter automatically converts based on the Object.toString()
of the selected item.
This converter is available by converter ID omnifaces.SelectItemsConverter. Just specify it in the
converter attribute of the selection component holding <f:selectItems>.
<h:selectOneMenu value="#{bean.selectedItem}" converter="omnifaces.SelectItemsConverter">
<f:selectItems value="#{bean.availableItems}" />
</h:selectOneMenu>
toString() implementation
The base converter uses by default the toString() method of the entity to uniquely identify
the instance during the conversion. This is sufficient if your (abstract base) entity has a
toString() implementation which looks something like this:
@Override
public String toString() {
return String.format("%s[id=%d]", getClass().getSimpleName(), getId());
}
By the way, you should also make sure that your entity
has a good equals() and hashCode() implementation, otherwise JSF won't be able
to set the right entity back in the model. Please note that this problem is in turn unrelated to the
SelectItemsConverter, you would have faced the same problem when using any other converter.
toString() implementation
However, if the entity doesn't have a toString() implementation (and thus relies on the default
fqn@hashcode implementation), or the existing implementation doesn't necessarily uniquely
identify the instance, and you can't implement/change it, then it is recommended to extend the
SelectItemsConverter class and override only the getAsString method wherein
the desired implementation is provided. For example:
@FacesConverter("exampleEntitySelectItemsConverter")
public class ExampleEntitySelectItemsConverter extends SelectItemsConverter {
@Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
Long id = (value instanceof ExampleEntity) ? ((ExampleEntity) value).getId() : null;
return (id != null) ? String.valueOf(id) : null;
}
}
Again, you do not need to override the getAsObject() method which would only
need to perform possibly expensive service/DAO operations. The SelectItemsConverter base
converter will already do it automatically based on the available items and the getAsString()
implementation.
An alternative is to switch to SelectItemsIndexConverter, which will convert based on the position (index)
of the selected item in the list instead of the Object.toString() of the selected item.
SelectItemsUtils,
SelectItemsCollector| Constructor and Description |
|---|
SelectItemsConverter() |
| Modifier and Type | Method and Description |
|---|---|
Object |
getAsObject(FacesContext context,
UIComponent component,
String value) |
String |
getAsString(FacesContext context,
UIComponent component,
Object value) |
public Object getAsObject(FacesContext context, UIComponent component, String value)
getAsObject in interface Converterpublic String getAsString(FacesContext context, UIComponent component, Object value)
getAsString in interface ConverterCopyright © 2012–2015 OmniFaces. All rights reserved.