How to convert String to an enum value when an enum type reference is a class <?>?

Question

I have code that sets values ​​for an object using its configuration methods. One of the filters accepts an Enum type as a method parameter. The code looks something like this:

String value = "EnumValue1"; Method setter = getBeanWriteMethod("setMyEnumValue"); Class<?> type = setter.getParameterTypes()[0]; Object convertedValue = null; if (type.isEnum()) { convertedValue = convertToEnum(value, type); } else { convertedValue = ClassUtils.convertType(value, type); } return convertedValue; 

The question is what to add the convertToEnum method. I know that I could "translate it by force" by iterating the enumeration constants (or fields) of the type object, matching the value. Can I skip the simpler way to do this with Reflection? (I looked at a few examples, but did not find where the listing was known only through the class).

Answer 1

Above my head:

  Enum<?> convertedValue = Enum.valueOf((Class<Enum>)type, value); 

This converts the string to an enum constant of the Enum class of type

Change Now that I have a computer, I see what actually works. Any of the following cases worked correctly without compiler warnings:

 Enum<?> convertedValueA = Enum.valueOf(type, value); Enum<?> convertedValueB = Enum.valueOf(type.asSubclass(Enum.class), value); 

The second one calls asSubClass (), which would perform a runtime check so that type some enum class, but the valueOf() method must do this check anyway in order to work correctly.

The following gave me a compilation error:

 Enum<?> convertedValueC = Enum.valueOf((Class<? extends Enum <?>>)type, value); java: Foo.java:22: <T>valueOf(java.lang.Class<T>,java.lang.String) in java.lang.Enum cannot be applied to (java.lang.Class<capture#134 of ? extends java.lang.Enum<?>>,java.lang.String) 

The intricacies of casting for wildcard types confuse me, so I probably tried the wrong translation. Plus, the fact that it does not have a runtime effect means that it is easily mistaken and will never know.

Answer 2

you can use

 Class enumType = .... String name = .... Enum e = Enum.valueOf(enumType, name); 

eg.

 import java.lang.annotation.*; public class Main { public static void main(String[] args) { Class enumType = RetentionPolicy.class; String name = "SOURCE"; Enum e = Enum.valueOf(enumType, name); System.out.println(e); } } 

prints

 SOURCE 

Answer 3

 Enum.valueOf(yrEnum, myString) 

Returns an enumeration, where myString is the name of the required enumeration instance. And yrEnum.values() returns an array of all possible Enums instances.