JSF converter implementation notes

SEAM's built-in converters are big time-savers, especially the s:convertEntity and s:convertEnum. Now the needs of rolling out customized JSF converters are few and far between, I just want to jot down the patterns I had used in case I forget.

1. take the entity's primary ID as string, and load it from persistence media by ID to convert back to object


2. implement an algorithm that can encode the object into a unique string, and reconstruct the object by parsing the string


3. Construct a map of strings and objects. Because converters are instantiated on demand, you have to save the map in a backing bean whose life-cycle spans over requests. The map is nested in the h:selectOneMenu component using f:attribute tag, so that the converter can get a handle of it.
   <br /><h:selectOneMenu id="dropDown" value="#{bean.selectedOption}"><br /> <s:selectItems value="#{beanManager.options}" var="o" label="#{o.label}"/><br /> <f:attribute name="options" value="#{beanManager.options}"/><br /> </h:selectOneMenu><br />