EnumParamConverterProvider.java

package dev.resteasy.example;

import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Response;
import javax.ws.rs.ext.ParamConverter;
import javax.ws.rs.ext.ParamConverterProvider;
import javax.ws.rs.ext.Provider;

/**
 * @author <a href="mailto:jperkins@redhat.com">James R. Perkins</a>
 */
@Provider
public class EnumParamConverterProvider implements ParamConverterProvider {
    @Override
    public <T> ParamConverter<T> getConverter(final Class<T> rawType, final Type genericType, final Annotation[] annotations) {
        if (!rawType.isEnum()) {
            return null;
        }
        final Enum<?>[] constants = (Enum<?>[]) rawType.getEnumConstants();
        return new ParamConverter<T>() {
            @Override
            @SuppressWarnings("unchecked")
            public T fromString(final String value) {
                if (value == null || value.isEmpty()) {
                    return null;
                }
                for (Enum<?> e : constants) {
                    if (e.name().equalsIgnoreCase(value)) {
                        return (T) e;
                    }
                }
                // No match, check toString()
                for (Enum<?> e : constants) {
                    if (e.toString().equalsIgnoreCase(value)) {
                        return (T) e;
                    }
                }
                try {
                    final int ordinal = Integer.parseInt(value) - 1;
                    if (ordinal >= 0 && constants.length >= ordinal) {
                        return (T) constants[ordinal];
                    }
                } catch (NumberFormatException ignore) {
                }
                throw new WebApplicationException(Response.status(Response.Status.BAD_REQUEST)
                        .entity(String.format("Failed to find constant '%s'", value))
                        .build());
            }

            @Override
            public String toString(final T value) {
                return value != null ? value.toString() : null;
            }
        };
    }
}