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The basic module that defines basic RxMicro annotations, required when using the REST architecture of building program systems.
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/*
 * Copyright (c) 2020. https://rxmicro.io
 *
 * 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.rxmicro.rest;

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

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.SOURCE;

/**
 * Maps HTTP parameter extracted from HTTP body or HTTP query string to annotated class field.
 *
 * 
 * The RxMicro framework uses the following algorithm to define the HTTP parameter name for the specified model field:
 * 

 *     
 *         If the field is annotated by the {@link Parameter} annotation with an explicit indication of the HTTP parameter name,
 *         the specified name is used.
 *     
 *     
 *         If no HTTP parameter name is specified in the {@link Parameter} annotation, the RxMicro framework checks for the
 *         {@link ParameterMappingStrategy} annotation above the model class.
 *     
 *     
 *         If the model class is annotated by the  {@link ParameterMappingStrategy} annotation, then the specified naming strategy is used.
 *         (The field name is used as the basic name, and then, following the rules of the specified strategy,
 *         the HTTP parameter name is generated.)
 *     
 *     
 *         If the {@link ParameterMappingStrategy} annotation is missing, the model class field name is used as the HTTP parameter name.
 *     
 * 
 *
 * 
 * The RxMicro framework supports the following Java types, which can be HTTP request model parameters:
 * 

 *     ? extends {@link Enum}<?>
 *     {@link Boolean}
 *     {@link Byte}
 *     {@link Short}
 *     {@link Integer}
 *     {@link Long}
 *     {@link java.math.BigInteger}
 *     {@link Float}
 *     {@link Double}
 *     {@link java.math.BigDecimal}
 *     {@link Character}
 *     {@link String}
 *     {@link java.time.Instant}
 *     ? extends {@link Object}
 *     {@link java.util.List}<PRIMITIVE>
 *     {@link java.util.List}<? extends {@link Object}>
 * 
 *
 * 
 * Note that RxMicro does not distinguish whether HTTP request parameters will be transferred to the handler using the start line or
 * HTTP body! Therefore, if the parameters are the same, it is possible to use the same handler with the specified request model to
 * handle both GET (parameters are transferred in the start line) and POST (parameters are transferred in the HTTP body) request.
 *
 * @author nedis
 * @see AddQueryParameter
 * @see SetQueryParameter
 * @see RepeatQueryParameter
 * @see ParameterMappingStrategy
 * @since 0.1
 */
@Documented
@Retention(SOURCE)
@Target({FIELD, METHOD, PARAMETER})
public @interface Parameter {

    /**
     * By default, HTTP parameter name equals to field name.
     *
     * @return the HTTP parameter name
     */
    String value() default "";
}