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-
  • GenericEnumConverter
  • ListConverter
  • ListIndexConverter
  • SelectItemsConverter
  • SelectItemsIndexConverter
  • ValueChangeConverter

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.

Usage

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>

Make sure that your entity has a good 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.

If your entity can't have a good 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.

Demo

The below demo uses the base converter only, as ExampleEntity already returns its unique identifier in the toString() method. If you intend to use the extended select items converter for your entities based on the above example, then just specify the converter as converter="exampleEntitySelectItemsConverter" instead.

Last selected item:

Demo source code
<p>
    The below demo uses the base converter only, as <code>ExampleEntity</code> already returns its unique 
    identifier in the <code>toString()</code> method. If you intend to use the extended select items converter
    for your entities based on the above example, then just specify the converter as 
    <code>converter="exampleEntitySelectItemsConverter"</code> instead.
</p>

<h:form>
    <p>
        <b>Last selected item:</b> <h:outputText id="selected_item" value="#{selectItemsBean.selectedEntity.value}" />
    </p>
    
    <h:panelGrid columns="2">
        <h:outputLabel for="iterator" value="Items with iterator: " />
        <h:selectOneMenu id="iterator" value="#{selectItemsBean.selectedEntity}" converter="omnifaces.SelectItemsConverter">
            <f:selectItem itemLabel="Choose item" noSelectionOption="true" />
            <f:selectItems value="#{selectItemsBean.exampleEntities}" var="entity" itemLabel="#{entity.value}" itemValue="#{entity}" />
            <f:ajax render="selected_item" />
        </h:selectOneMenu>

        <h:outputLabel for="iterator_def_value" value="Items with iterator (default value): " />
        <h:selectOneMenu id="iterator_def_value" value="#{selectItemsBean.selectedEntity}" converter="omnifaces.SelectItemsConverter">
            <f:selectItem itemLabel="Choose item" noSelectionOption="true" />
            <f:selectItems value="#{selectItemsBean.exampleEntities}" var="entity" itemLabel="#{entity.value}" />
            <f:ajax render="selected_item" />
        </h:selectOneMenu>

        <h:outputLabel for="selectitems" value="Items with SelectItem list: " />
        <h:selectOneMenu id="selectitems" value="#{selectItemsBean.selectedEntity}" converter="omnifaces.SelectItemsConverter">
            <f:selectItem itemLabel="Choose item" noSelectionOption="true" />
            <f:selectItems value="#{selectItemsBean.selectItems}" />
            <f:ajax render="selected_item" />
        </h:selectOneMenu>

        <h:outputLabel for="selectitems_array" value="Items with SelectItem array: " />
        <h:selectOneMenu id="selectitems_array" value="#{selectItemsBean.selectedEntity}" converter="omnifaces.SelectItemsConverter">
            <f:selectItem itemLabel="Choose item" noSelectionOption="true" />
            <f:selectItems value="#{selectItemsBean.selectItemArray}" />
            <f:ajax render="selected_item" />
        </h:selectOneMenu>
    </h:panelGrid>
</h:form>