Java Generic Enum class using Reflection

Question

In our code there are 10's of enum classes with same template code pasted each and every time when ever a new enum class needs to be created.

Need a way to generic way to avoid duplication of this code.

Below are couple of same enums classes

Class-1

 public enum AccountStatus {

ACTIVE("ACTIVE", 1), 
INACTIVE("INACTIVE", 2);

private final int value;

private final String key;

AccountStatus(String key, int value) {
    this.value = value;
    this.key = key;
}

public int getValue() {
    return this.value;
}

public String getKey() {
    return this.key;
}

@Override
public String toString() {
    return String.valueOf(this.value);
}

@JsonCreator
public static AccountStatus create(String key) {
    if (key == null) {
        throw new IllegalArgumentException();
    }
    for (AccountStatus v : values()) {
        if (v.getKey().equalsIgnoreCase(key)) {
            return v;
        }
    }
    throw new IllegalArgumentException();
}

public static AccountStatus fromValue(Integer value) {

    for (AccountStatus type : AccountStatus.values()) {
        if (value == type.getValue()) {
            return type;
        }
    }
    throw new IllegalArgumentException("Invalid enum type supplied");
}

public static AccountStatus fromValue(String key) {

    for (AccountStatus type : AccountStatus.values()) {
        if (type.getKey().equalsIgnoreCase(key)) {
            return type;
        }
    }
    throw new IllegalArgumentException("Invalid enum type supplied");
}
 }

Class-2

      public enum Gender {

MALE("MALE", 1), 
FEMALE("FEMALE", 2);

private final int value;

private final String key;

Gender(String key, int value) {
    this.value = value;
    this.key = key;
}

public int getValue() {
    return this.value;
}

public String getKey() {
    return this.key;
}

@Override
public String toString() {
    return String.valueOf(this.value);
}

@JsonCreator
public static Gender create(String key) {
    if (key == null) {
        throw new IllegalArgumentException();
    }
    for (Gender v : values()) {
        if (v.getKey().equalsIgnoreCase(key)) {
            return v;
        }
    }
    throw new IllegalArgumentException();
}

public static Gender fromValue(Integer value) {

    for (Gender type : Gender.values()) {
        if (value == type.getValue()) {
            return type;
        }
    }
    throw new IllegalArgumentException("Invalid enum type supplied");
}

public static Gender fromValue(String gender) {

    for (Gender type : Gender.values()) {
        if (type.getKey().equalsIgnoreCase(gender)) {
            return type;
        }
    }
    throw new IllegalArgumentException("Invalid enum type supplied");
}

}

Need a generic a solution which handles all the methods in class.

i mean key is just `name()` and value is `ordinal() + 1` so eh — EpicPandaForce, May 03 '17 at 20:29
http://stackoverflow.com/questions/15450897/how-to-extend-enum-class-from-abstract-class — rj2700, May 03 '17 at 20:53

score 3 · Accepted Answer · answered May 03 '17 at 22:14

3

Two options that I can see, and both involve interfaces. In either case though, you will still need to make the constructor for your enum and declare the fields.

Implement an interface on your enum for the getValue and getKey methods, and then move the create and fromValue methods to a utility class that takes the enum class as a parameter. e.g.

EnumUtility.create(AccountStatus.class, "ACTIVE");

Use JDK8 interfaces to declare default method implementations that will be inherited into your enum.

answered May 03 '17 at 22:14

Trevor Freeman

7,112
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@Shoaib627 The answer here has an example that is nearish to some of what you want to do: http://stackoverflow.com/a/22102121/1074041 – Trevor Freeman May 08 '17 at 19:37
Can u have a look at his : http://stackoverflow.com/questions/43895415/java-generic-enum-functionality-using-java-8-default-methods-and-utility-class?noredirect=1#comment74825533_43895415 – shoaib1992 May 10 '17 at 15:27

Java Generic Enum class using Reflection

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