Question

我已经看过很多关于如何在编译时知道Enum类动态获取枚举值的StackOverflow帖子，但我试图动态加载枚举类和枚举值，我不是看看如何做到这一点。

我正在尝试做这样的事情：

public interface Config {
    public ConfigValue getConfigValue();
}

public enum AwsConfig implements Config {
    ACCESS_KEY_ID( new ConfigValue(...) ),
    API_URL( new ConfigValue(...) )
    ...
    public static String getName() { return "AwsConfig"; }
    ...
}

public enum PaginatorConfig implements Config {
    DEFAULT_PAGE_SIZE( new ConfigValue(...) ),
    ...
    public static String getName() { return "PaginatorConfig"; }
    ...
}

public void myMethod( ConfigValue configValue ) {
    String enumClassName = configValue.getName();
    String enumConstantKeyName = configValue.getKey();

    // I now have the enum's class name as enumClassName
    // I now have the enum constant's name as enumConstantKeyName
    // How can I dynamically get the enum constant's configValue based on the enumClassName and enumConstantKeyName?

    // I know I can get the value dynamically if I know the Enum constant...
    ConfigValue configValue = AwsConfig.valueOf("API_URL")

    // But I wish I could do something like this...
    ConfigValue configValue = Enum.valueOf( "AwsConfig", "API_URL" );
}

Answer 1

如果您知道（或可以弄清楚）要从中加载值的枚举的完全限定类名，则可以执行以下操作：

String enumClassName = "com.mycompany.MyEnum";
String enumConstant = "MyValue";

Class enumClass = Class.forName(enumClassName);
Object enumValue = Enum.valueOf(enumClass, enumConstant);

assert enumValue == MyEnum.MyValue; // passes

Answer 2

您可以使用反射。这是一个简短的例子：

public class Test {

    public enum TestEnum {

        MyEnumValue1,

        MyEnumValue2;
    }

    public static void main(String[] args) {
        try {
            Object enumValue = getEnumValue("test.Test$TestEnum", "MyEnumValue2");
            System.out.println(enumValue.getClass().getName() + " = "
                    + enumValue);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public static Object getEnumValue(String enumClassName, String enumValueName)
            throws ClassNotFoundException, NoSuchMethodException,
            SecurityException, IllegalAccessException,
            IllegalArgumentException, InvocationTargetException {
        Class<?> enumClass = Class.forName(enumClassName);
        Method valueOfMethod = enumClass.getDeclaredMethod("valueOf",
            String.class);
        return valueOfMethod.invoke(null, enumValueName);
    }
}

动态加载Java Enum类和枚举常量

2 个答案: