001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
004//
005// http://www.apache.org/licenses/LICENSE-2.0
006//
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
012
013package org.apache.tapestry5.annotations;
014
015import static java.lang.annotation.ElementType.PARAMETER;
016import static java.lang.annotation.RetentionPolicy.RUNTIME;
017import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.PAGE;
018
019import java.lang.annotation.Documented;
020import java.lang.annotation.Retention;
021import java.lang.annotation.Target;
022
023import org.apache.tapestry5.commons.services.TypeCoercer;
024import org.apache.tapestry5.http.services.HttpRequestBodyConverter;
025import org.apache.tapestry5.internal.transform.OnEventWorker;
026import org.apache.tapestry5.ioc.annotations.UseWith;
027
028/**
029 * Annotation that may be placed on parameters of event handler methods,
030 * usually in page classes.
031 * Annotated parameters will be extracted fro the request body and converted
032 * to the parameter type using {@linkplain HttpRequestBodyConverter}, which uses 
033 * {@linkplain TypeCoercer} as a fallback.
034 * An event handler method having more than one {@linkplain RequestBody} 
035 * parameter is considered an error.
036 * 
037 * @since 5.8.0
038 * @see OnEventWorker
039 */
040@Target(
041{ PARAMETER })
042@Retention(RUNTIME)
043@Documented
044@UseWith(
045{ PAGE })
046public @interface RequestBody
047{
048    /**
049     * If false (the default), then an exception is thrown when the request body is empty (i.e. zero bytes).
050     * If true, then empty bodies are allowed and the parameter will receive a null value.
051     */
052    boolean allowEmpty() default false;
053}