serialization - Are there good alternatives for serializing enums in Java? -

the java language benefited adding enums it; unfortunately don't work when sending serialized objects between systems have different code levels.

example: assume have 2 systems , b. both start of same code levels, @ point start see code updates @ different points in time. assume there

public enum whatever { first; } 

and there other objects keep references constants of enum. objects serialized , sent b or vice versa. consider b has newer version of whatever

public enum whatever { first; second } 

then:

class somethingelse implements serializable { ...   private final whatever thewhatever;   somethingelse(whatever thewhatever) {     this.thewhatever = thewhatever; .. 

gets instantiated ...

somethingelse somethin = new somethingelse(whatever.second) 

and serialized , sent on (for example result of rmi call). bad, because there error during deserialization on a: knows whatever enum class, in version doesn't have second.

we figured hard way; , anxious use enums situations "perfect enums"; because know can't extend existing enum later on.

now wondering: there (good) strategies avoid such compatibility issues enums? or have go "pre-enum" times; , don't use enums, have rely on solution use plain strings on place?

update: please note using serialversionuid doesn't here @ all. thing helps in making incompatible change "more obvious". point is: don't care why deserialization fails - because have avoid happen. , not in position change way serialize our objects. doing rmi; , serializing binary; have no means change that.

as @jesper mentioned in comments, recommend json inter-service communication. allow have more control on how unknown enum values handled.

for example, using awesome jackson can use deserialization features read_unknown_enum_values_as_null or read_unknown_enum_values_using_default_value. both allow application logic handle unknown enum values see fit.

example (straight jackson doc)

enum myenum { a, b, @jsonenumdefaultvalue unknown } ... final objectmapper mapper = new objectmapper(); mapper.enable(deserializationfeature.read_unknown_enum_values_using_default_value);  myenum value = mapper.readvalue("\"foo\"", myenum.class); assertsame(myenum.unknown, value);