Module org.omnifaces
Package org.omnifaces.converter

Class GenericEnumConverter

  • All Implemented Interfaces:
    Converter<Enum>
    public class GenericEnumConverter
extends Object
implements Converter<Enum>

    The omnifaces.GenericEnumConverter is intended for use in UISelectMany components whose value is been bound to a List<E> property where E is an enum. Even though Faces has already a built-in EnumConverter, this doesn't work for a List<E> property as the generic type information E is lost during runtime. The list would be filled with unconverted String values instead which may in turn cause ClassCastException during postprocessing in the business logic.

    This can be solved by using a E[] property instead of List<E> (e.g. Role[] in case of a Role enum). If this is however is not an option due to some design restrictions (e.g. JPA @ElementCollection, etc), then you'd need to create an explicit converter for the enum type like follows: 

     @FacesConverter("roleConverter")
 public class RoleConverter extends EnumConverter {
     public RoleConverter() {
         super(Role.class);
     }
 }
 
     <h:selectManyCheckbox value="#{bean.selectedRoles}" converter="roleConverter">
     <f:selectItems value="#{bean.availableRoles}" />
 </h:selectManyCheckbox>

    However, creating a new converter for every single enum type, only and only for use in UISelectMany with a List<E> property, may be a bit clumsy. This generic enum converter is intended to remove the need to create a new enum converter every time.

    Usage

    This converter is available by converter ID omnifaces.GenericEnumConverter. Just specify it in the converter attribute of the multi-selection component holding <f:selectItems>. example: 

     <h:selectManyCheckbox value="#{bean.selectedEnums}" converter="omnifaces.GenericEnumConverter">
     <f:selectItems value="#{bean.availableEnums}" />
 </h:selectManyCheckbox>

    Since OmniFaces 4.5 it's also available by <o:genericEnumConverter> tag. 

     <h:selectManyCheckbox value="#{bean.selectedEnums}">
     <f:selectItems value="#{bean.availableEnums}" />
     <o:genericEnumConverter />
 </h:selectManyCheckbox>

    See also:
    Use enum in <h:selectManyCheckbox>

    JSF 2.3

    This converter is not necessary anymore since JSF 2.3 thanks to the fixes in issue 1422. 

     <h:selectManyCheckbox value="#{bean.selectedEnums}">
     <f:selectItems value="#{bean.availableEnums}" />
 </h:selectManyCheckbox>

    However, when you're having an input component without a value attribute, and thus the exact type cannot be automatically determined by simply inspecting the return type of the associated getter method, then this converter may be still useful. 

     <h:selectManyCheckbox converter="omnifaces.GenericEnumConverter">
     <f:selectItems value="#{bean.availableEnums}" />
 </h:selectManyCheckbox>
    Since:
    1.2
    Author:
    Bauke Scholtz