io.github.mtrevisan.boxon.annotations.ObjectChoices Maven / Gradle / Ivy

/**
 * Copyright (c) 2020 Mauro Trevisan
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
package io.github.mtrevisan.boxon.annotations;

import io.github.mtrevisan.boxon.external.ByteOrder;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


/**
 * Allow to define a number of choices, based on a prefix of a certain {@link #prefixSize() size}.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.ANNOTATION_TYPE)
@Documented
public @interface ObjectChoices{

	/**
	 * The number of bits to be read for determining the prefix.
	 *
	 * @return	The number of bits to be read for determining the prefix (defaults to {@code 0}).
	 */
	int prefixSize() default 0;

	/**
	 * The byte order to take into account when returning a representation of the first {@link #prefixSize() size} bits
	 * read as a prefix.
	 *
	 * @return	The byte order to take into account when returning a representation of the first {@link #prefixSize()
	 * 	size} bits read as a prefix (defaults to {@link ByteOrder#BIG_ENDIAN}).
	 */
	ByteOrder byteOrder() default ByteOrder.BIG_ENDIAN;

	/**
	 * The choices to select from.
	 *
	 * @return	The choices to select from (defaults to no alternatives).
	 */
	ObjectChoice[] alternatives() default {};


	/** The annotation holding a single choice. */
	@Retention(RetentionPolicy.RUNTIME)
	@Target(ElementType.ANNOTATION_TYPE)
	@Documented
	@interface ObjectChoice{

		/**
		 * The condition that needs to hold, if an instance of {@link #type() type} is to be decoded.
		 * A SpEL expression with the prefix value in the context under the name `{@code prefix}`.
		 *
		 * @return	The condition that needs to hold, if an instance of {@link #type() type} is to be decoded.
		 */
		String condition();

		/**
		 * The prefix to be written when serializing the object.
		 * NOTE: this SpEL expression returns the prefix value, that is, the inverse of {@link #condition() condition}.
		 *
		 * @return	A SpEL expression which returns the prefix value, that is, the inverse of {@link #condition() condition} (defaults to {@code 0}).
		 */
		long prefix() default 0l;

		/**
		 * The type to decode in case the {@link #condition()} holds.
		 *
		 * @return	The type to decode in case the {@link #condition()} holds.
		 */
		Class type();

	}

}