/*
 * Copyright 2002-2018 the original author or authors.
 *
 * 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 org.springframework.web.bind.annotation;

import java.beans.PropertyEditor;
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;

import org.springframework.core.annotation.AliasFor;
import org.springframework.core.convert.converter.Converter;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartResolver;

Annotation that can be used to associate the part of a "multipart/form-data" request
with a method argument.
Supported method argument types include MultipartFile in conjunction with Spring's MultipartResolver abstraction, javax.servlet.http.Part in conjunction with Servlet 3.0 multipart requests, or otherwise for any other method argument, the content of the part is passed through an HttpMessageConverter taking into consideration the 'Content-Type' header of the request part. This is analogous to what @RequestBody does to resolve an argument based on the content of a non-multipart regular request. 
Note that @RequestParam annotation can also be used to associate the part of a "multipart/form-data" request with a method argument supporting the same method argument types. The main difference is that when the method argument is not a String or raw MultipartFile / Part, @RequestParam relies on type conversion via a registered Converter or PropertyEditor while RequestPart relies on HttpMessageConverters taking into consideration the 'Content-Type' header of the request part. RequestParam is likely to be used with name-value form fields while RequestPart is likely to be used with parts containing more complex content e.g. JSON, XML). 
Author:
Rossen Stoyanchev, Arjen Poutsma, Sam Brannen
See Also:
RequestParam
RequestMappingHandlerAdapter
Since:
3.1/**
 * Annotation that can be used to associate the part of a "multipart/form-data" request
 * with a method argument.
 *
 * <p>Supported method argument types include {@link MultipartFile} in conjunction with
 * Spring's {@link MultipartResolver} abstraction, {@code javax.servlet.http.Part} in
 * conjunction with Servlet 3.0 multipart requests, or otherwise for any other method
 * argument, the content of the part is passed through an {@link HttpMessageConverter}
 * taking into consideration the 'Content-Type' header of the request part. This is
 * analogous to what @{@link RequestBody} does to resolve an argument based on the
 * content of a non-multipart regular request.
 *
 * <p>Note that @{@link RequestParam} annotation can also be used to associate the part
 * of a "multipart/form-data" request with a method argument supporting the same method
 * argument types. The main difference is that when the method argument is not a String
 * or raw {@code MultipartFile} / {@code Part}, {@code @RequestParam} relies on type
 * conversion via a registered {@link Converter} or {@link PropertyEditor} while
 * {@link RequestPart} relies on {@link HttpMessageConverter HttpMessageConverters}
 * taking into consideration the 'Content-Type' header of the request part.
 * {@link RequestParam} is likely to be used with name-value form fields while
 * {@link RequestPart} is likely to be used with parts containing more complex content
 * e.g. JSON, XML).
 *
 * @author Rossen Stoyanchev
 * @author Arjen Poutsma
 * @author Sam Brannen
 * @since 3.1
 * @see RequestParam
 * @see org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter
 */
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestPart {

	
Alias for name. /**
	 * Alias for {@link #name}.
	 */
	@AliasFor("name")
	String value() default "";

	
The name of the part in the "multipart/form-data" request to bind to. 
Since:
4.2/**
	 * The name of the part in the {@code "multipart/form-data"} request to bind to.
	 * @since 4.2
	 */
	@AliasFor("value")
	String name() default "";

	
Whether the part is required.
Defaults to true, leading to an exception being thrown if the part is missing in the request. Switch this to false if you prefer a null value if the part is not present in the request. /**
	 * Whether the part is required.
	 * <p>Defaults to {@code true}, leading to an exception being thrown
	 * if the part is missing in the request. Switch this to
	 * {@code false} if you prefer a {@code null} value if the part is
	 * not present in the request.
	 */
	boolean required() default true;

}