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Pdef java descriptors, formats and RPC
There is a newer version: 1.2.0
/*
 * Copyright: 2013 Pdef 
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.pdef.descriptors;

import io.pdef.TypeEnum;

import javax.annotation.Nullable;
import java.lang.reflect.Field;
import java.util.Date;

/** Primitive and collection descriptors. */
public class Descriptors {
	public static DataTypeDescriptor bool = primitive(TypeEnum.BOOL, Boolean.class, false);
	public static DataTypeDescriptor int16 = primitive(TypeEnum.INT16, Short.class, (short) 0);
	public static DataTypeDescriptor int32 = primitive(TypeEnum.INT32, Integer.class, 0);
	public static DataTypeDescriptor int64 = primitive(TypeEnum.INT64, Long.class, 0L);
	public static DataTypeDescriptor float0 = primitive(TypeEnum.FLOAT, Float.class, 0f);
	public static DataTypeDescriptor double0 = primitive(TypeEnum.DOUBLE, Double.class, 0d);
	public static DataTypeDescriptor string = primitive(TypeEnum.STRING, String.class, "");
	public static DataTypeDescriptor datetime = primitive(TypeEnum.DATETIME, Date.class, null);
	public static DataTypeDescriptor void0 = primitive(TypeEnum.VOID, Void.class, null);

	private Descriptors() {}

	public static  ListDescriptor list(final DataTypeDescriptor element) {
		return new ListDescriptor(element);
	}

	public static  SetDescriptor set(final DataTypeDescriptor element) {
		return new SetDescriptor(element);
	}

	public static  MapDescriptor map(final DataTypeDescriptor key,
			final DataTypeDescriptor value) {
		return new MapDescriptor(key, value);
	}

	private static  PrimitiveDescriptor primitive(final TypeEnum type, final Class cls,
			final T defaultValue) {
		return new PrimitiveDescriptor(type, cls, defaultValue);
	}

	/** Returns an interface descriptor or throws an IllegalArgumentException. */
	@Nullable
	public static  InterfaceDescriptor findInterfaceDescriptor(final Class cls) {
		if (!cls.isInterface()) {
			throw new IllegalArgumentException("Interface required, got " + cls);
		}

		Field field;
		try {
			field = cls.getField("DESCRIPTOR");
		} catch (NoSuchFieldException e) {
			throw new IllegalArgumentException("No DESCRIPTOR field in " + cls);
		}

		if (!InterfaceDescriptor.class.isAssignableFrom(field.getType())) {
			throw new IllegalArgumentException("Not an InterfaceDescriptor field, " + field);
		}

		try {
			// Get the static TYPE field.
			@SuppressWarnings("unchecked")
			InterfaceDescriptor descriptor = (InterfaceDescriptor) field.get(null);
			return descriptor;
		} catch (IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

	private static class PrimitiveDescriptor extends DataTypeDescriptor {
		private final T defaultValue;

		private PrimitiveDescriptor(final TypeEnum type, final Class javaClass,
				final T defaultValue) {
			super(type, javaClass);
			this.defaultValue = defaultValue;
		}

		@Override
		public T getDefault() {
			return defaultValue;
		}
	}
}