Elegant way to deserialise EnumSet from String

Question

I'd like to serialise some EnumSet<FooType> to String using its toString() method.

E.g.: EnumSet.of(FooType.COMMON, FooType.MEDIUM).toString() will give [COMMON, MEDIUM].

The question is about an elegant way to deserialise such a string back to the EnumSet<FooSet>. I'm looking for some commonly known library (may be like apache-commons) or a standard Util-class for such things.

Something like: EnumSetUtil.valueOf(FooType.class, "[COMMON, MEDIUM]")

I've implemented this thing in such way:

public static <E extends Enum<E>> EnumSet<E> valueOf(Class<E> eClass, String str) {
    String[] arr = str.substring(1, str.length() - 1).split(",");
    EnumSet<E> set = EnumSet.noneOf(eClass);
    for (String e : arr) set.add(E.valueOf(eClass, e.trim()));
    return set;
}

But, may be there is a ready solution, or a dramatically easy way for doing this.

I know of no such library, and your method looks pretty good. I would probably use a regex (_personal preference_) instead, and call the method `fromString` to imply its inverse relationship to `toString` (though the java convention would likely be something like `parseEnumSet`), but I don't find any flaw in what you are doing. — Lucas, Mar 28 '13 at 15:25
Serializing and deserializing "by hand" is often faster and easier to debug for simple structures but you usually hit pretty fast the corner cases: for example what happens if one your enums contains a comma `,` ? Then you will need to start escaping commas and complicate your regex, etc.. — Bruno Grieder, Mar 28 '13 at 16:14

score 7 · Accepted Answer · edited Jul 14 '16 at 05:55

7

With Java 8 you can do something like this with Lambda expressions and streams:

EnumSet.copyOf(Arrays.asList(str.split(","))
.stream().map(FooType::valueOf).collect(Collectors.toList()))

edited Jul 14 '16 at 05:55

Basil Bourque

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answered Jul 31 '15 at 10:50

anho-dev

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Anderson · Answer 2 · 2015-11-05T09:54:10.917

0

With guava 19.0:

    Iterable<String> i = Splitter.on(",")
        .trimResults(CharMatcher.WHITESPACE.or(CharMatcher.anyOf("[]")))
        .split(str);
    Set<YourEnum> result = FluentIterable.from(i)
        .transform(Enums.stringConverter(YourEnum.class)).toSet();

OR another way with JSON library if you can accept String format like this ['COMMON', 'MEDIUM'].

edited Nov 05 '15 at 09:54

answered Nov 05 '15 at 08:18

Anderson

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score 0 · Answer 3 · answered Mar 16 '16 at 08:04

Using Gson ('com.google.code.gson:gson:2.3.1') library you can do:

public static EnumSet getEnumObject(Type type, String jsonStrToDeserialize) {
    Gson gson = new Gson();
    return jsonStrToDeserialize == null ? null : (EnumSet) gson.fromJson(jsonStrToDeserialize, type);
}

Elegant way to deserialise EnumSet from String

3 Answers3