HttpMessageConverter.java

/*
 * Copyright 2011 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.async.http.converter;

import java.io.IOException;
import java.util.List;

import org.springframework.async.Promise;
import org.springframework.async.http.HttpInputMessage;
import org.springframework.async.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

/**
 * @author Jon Brisbin <jon@jbrisbin.com>
 */
public interface HttpMessageConverter<T> {

	/**
	 * Indicates whether the given class can be read by this converter.
	 *
	 * @param clazz		 the class to test for readability
	 * @param mediaType the media type to read, can be {@code null} if not specified.
	 *                  Typically the value of a {@code Content-Type} header.
	 * @return {@code true} if readable; {@code false} otherwise
	 */
	boolean canRead(Class<?> clazz, MediaType mediaType);

	/**
	 * Indicates whether the given class can be written by this converter.
	 *
	 * @param clazz		 the class to test for writability
	 * @param mediaType the media type to write, can be {@code null} if not specified.
	 *                  Typically the value of an {@code Accept} header.
	 * @return {@code true} if writable; {@code false} otherwise
	 */
	boolean canWrite(Class<?> clazz, MediaType mediaType);

	/**
	 * Return the list of {@link MediaType} objects supported by this converter.
	 *
	 * @return the list of supported media types
	 */
	List<MediaType> getSupportedMediaTypes();

	/**
	 * Read an object of the given type form the given input outputMessage, and returns it.
	 *
	 * @param clazz				the type of object to return. This type must have previously been passed to the
	 *                     {@link #canRead canRead} method of this interface, which must have returned {@code true}.
	 * @param inputMessage the HTTP input inputMessage to read from
	 * @return the converted object
	 * @throws java.io.IOException in case of I/O errors
	 * @throws org.springframework.http.converter.HttpMessageNotReadableException
	 *                             in case of conversion errors
	 */
	void read(Class<? extends T> clazz, HttpInputMessage inputMessage, Promise<T> promise)
			throws IOException, HttpMessageNotReadableException;

	/**
	 * Write an given object to the given output message.
	 *
	 * @param t						 the object to write to the output message. The type of this object must have previously been
	 *                      passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}.
	 * @param contentType	 the content type to use when writing. May be {@code null} to indicate that the
	 *                      default content type of the converter must be used. If not {@code null}, this media type must have
	 *                      previously been passed to the {@link #canWrite canWrite} method of this interface, which must have
	 *                      returned {@code true}.
	 * @param outputMessage the message to write to
	 * @throws IOException in case of I/O errors
	 * @throws org.springframework.http.converter.HttpMessageNotWritableException
	 *                     in case of conversion errors
	 */
	void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException;

}