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/*
* Copyright 2002-2021 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
*
* https://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.http.converter;
import java.io.IOException;
import java.util.Collections;
import java.util.List;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
/**
* Strategy interface for converting from and to HTTP requests and responses.
*
* @author Arjen Poutsma
* @author Juergen Hoeller
* @author Rossen Stoyanchev
* @since 3.0
* @param the converted object type
* @see SmartHttpMessageConverter
*/
public interface HttpMessageConverter {
/**
* 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, @Nullable 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, @Nullable MediaType mediaType);
/**
* Return the list of media types supported by this converter. The list may
* not apply to every possible target element type and calls to this method
* should typically be guarded via {@link #canWrite(Class, MediaType)
* canWrite(clazz, null}. The list may also exclude MIME types supported
* only for a specific class. Alternatively, use
* {@link #getSupportedMediaTypes(Class)} for a more precise list.
* @return the list of supported media types
*/
List getSupportedMediaTypes();
/**
* Return the list of media types supported by this converter for the given
* class. The list may differ from {@link #getSupportedMediaTypes()} if the
* converter does not support the given Class or if it supports it only for
* a subset of media types.
* @param clazz the type of class to check
* @return the list of media types supported for the given class
* @since 5.3.4
*/
default List getSupportedMediaTypes(Class clazz) {
return (canRead(clazz, null) || canWrite(clazz, null) ?
getSupportedMediaTypes() : Collections.emptyList());
}
/**
* Read an object of the given type from the given input message, 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 message to read from
* @return the converted object
* @throws IOException in case of I/O errors
* @throws HttpMessageNotReadableException in case of conversion errors
*/
T read(Class clazz, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException;
/**
* Write a 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 HttpMessageNotWritableException in case of conversion errors
*/
void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException;
}