https://github.com/eclipse-ee4j/jaxrs-api: Jakarta RESTful Web Services API (Eclipse Foundation) 
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 * Copyright (c) 2010, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.ws.rs.ext;

import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;


Contract for a provider that supports the conversion of a stream to a Java type. A MessageBodyReader implementation may be annotated with Consumes to restrict the media types for which it will be considered suitable. 
 Providers implementing MessageBodyReader contract must be either programmatically registered in an API runtime or must be annotated with @Provider annotation to be automatically discovered by the runtime during a provider scanning phase. 


Author:Paul Sandoz, Marc Hadley
Type parameters:
  • <T> – Java type supported by the provider
See Also:
Since:1.0
/**
 * Contract for a provider that supports the conversion of a stream to a
 * Java type.
 *
 * A {@code MessageBodyReader} implementation may be annotated
 * with {@link javax.ws.rs.Consumes} to restrict the media types for which it will
 * be considered suitable.
 * <p>
 * Providers implementing {@code MessageBodyReader} contract must be either programmatically
 * registered in an API runtime or must be annotated with
 * {@link javax.ws.rs.ext.Provider &#64;Provider} annotation to be automatically discovered
 * by the runtime during a provider scanning phase.
 * </p>
 *
 * @param <T> Java type supported by the provider
 * @author Paul Sandoz
 * @author Marc Hadley
 * @see Provider
 * @see javax.ws.rs.Consumes
 * @since 1.0
 */
public interface MessageBodyReader<T> {

    
Ascertain if the MessageBodyReader can produce an instance of a particular type. The type parameter gives the class of the instance that should be produced, the genericType parameter gives the java.lang.reflect.Type of the instance that should be produced. E.g. if the instance to be produced is List<String>, the type parameter will be java.util.List and the genericType parameter will be java.lang.reflect.ParameterizedType. 
Params:
  • type –        the class of instance to be produced.
  • genericType – the type of instance to be produced. E.g. if the message body is to be converted into a method parameter, this will be the formal type of the method parameter as returned by Method.getGenericParameterTypes.
  • annotations – an array of the annotations on the declaration of the artifact that will be initialized with the produced instance. E.g. if the message body is to be converted into a method parameter, this will be the annotations on that parameter returned by Method.getParameterAnnotations.
  • mediaType –  the media type of the HTTP entity, if one is not specified in the request then application/octet-stream is used.
Returns:true if the type is supported, otherwise false.
/**
     * Ascertain if the MessageBodyReader can produce an instance of a
     * particular type. The {@code type} parameter gives the
     * class of the instance that should be produced, the {@code genericType} parameter
     * gives the {@link java.lang.reflect.Type java.lang.reflect.Type} of the instance
     * that should be produced.
     * E.g. if the instance to be produced is {@code List<String>}, the {@code type} parameter
     * will be {@code java.util.List} and the {@code genericType} parameter will be
     * {@link java.lang.reflect.ParameterizedType java.lang.reflect.ParameterizedType}.
     *
     * @param type        the class of instance to be produced.
     * @param genericType the type of instance to be produced. E.g. if the
     *                    message body is to be converted into a method parameter, this will be
     *                    the formal type of the method parameter as returned by
     *                    {@code Method.getGenericParameterTypes}.
     * @param annotations an array of the annotations on the declaration of the
     *                    artifact that will be initialized with the produced instance. E.g. if the
     *                    message body is to be converted into a method parameter, this will be
     *                    the annotations on that parameter returned by
     *                    {@code Method.getParameterAnnotations}.
     * @param mediaType   the media type of the HTTP entity, if one is not
     *                    specified in the request then {@code application/octet-stream} is
     *                    used.
     * @return {@code true} if the type is supported, otherwise {@code false}.
     */
    public boolean isReadable(Class<?> type, Type genericType,
                              Annotation[] annotations, MediaType mediaType);

    
Read a type from the InputStream. 
 In case the entity input stream is empty, the reader is expected to either return a Java representation of a zero-length entity or throw a NoContentException in case no zero-length entity representation is defined for the supported Java type. A NoContentException, if thrown by a message body reader while reading a server request entity, is automatically translated by the server runtime into a BadRequestException wrapping the original NoContentException and rethrown for a standard processing by the registered exception mappers. 


Params:
  • type –         the type that is to be read from the entity stream.
  • genericType –  the type of instance to be produced. E.g. if the message body is to be converted into a method parameter, this will be the formal type of the method parameter as returned by Method.getGenericParameterTypes.
  • annotations –  an array of the annotations on the declaration of the artifact that will be initialized with the produced instance. E.g. if the message body is to be converted into a method parameter, this will be the annotations on that parameter returned by Method.getParameterAnnotations.
  • mediaType –    the media type of the HTTP entity.
  • httpHeaders –  the read-only HTTP headers associated with HTTP entity.
  • entityStream – the InputStream of the HTTP entity. The caller is responsible for ensuring that the input stream ends when the entity has been consumed. The implementation should not close the input stream.
Throws:
  • IOException – if an IO error arises. In case the entity input stream is empty and the reader is not able to produce a Java representation for a zero-length entity, NoContentException is expected to be thrown.
  • WebApplicationException – 
                            if a specific HTTP error response needs to be produced.
                            Only effective if thrown prior to the response being committed.
Returns:the type that was read from the stream. In case the entity input stream is empty, the reader is expected to either return an instance representing a zero-length entity or throw a NoContentException in case no zero-length entity representation is defined for the supported Java type.
/**
     * Read a type from the {@link InputStream}.
     * <p>
     * In case the entity input stream is empty, the reader is expected to either return a
     * Java representation of a zero-length entity or throw a {@link javax.ws.rs.core.NoContentException}
     * in case no zero-length entity representation is defined for the supported Java type.
     * A {@code NoContentException}, if thrown by a message body reader while reading a server
     * request entity, is automatically translated by the server runtime into a {@link javax.ws.rs.BadRequestException}
     * wrapping the original {@code NoContentException} and rethrown for a standard processing by
     * the registered {@link javax.ws.rs.ext.ExceptionMapper exception mappers}.
     * </p>
     *
     * @param type         the type that is to be read from the entity stream.
     * @param genericType  the type of instance to be produced. E.g. if the
     *                     message body is to be converted into a method parameter, this will be
     *                     the formal type of the method parameter as returned by
     *                     {@code Method.getGenericParameterTypes}.
     * @param annotations  an array of the annotations on the declaration of the
     *                     artifact that will be initialized with the produced instance. E.g.
     *                     if the message body is to be converted into a method parameter, this
     *                     will be the annotations on that parameter returned by
     *                     {@code Method.getParameterAnnotations}.
     * @param mediaType    the media type of the HTTP entity.
     * @param httpHeaders  the read-only HTTP headers associated with HTTP entity.
     * @param entityStream the {@link InputStream} of the HTTP entity. The
     *                     caller is responsible for ensuring that the input stream ends when the
     *                     entity has been consumed. The implementation should not close the input
     *                     stream.
     * @return the type that was read from the stream. In case the entity input stream is empty, the reader
     *         is expected to either return an instance representing a zero-length entity or throw
     *         a {@link javax.ws.rs.core.NoContentException} in case no zero-length entity representation is
     *         defined for the supported Java type.
     * @throws java.io.IOException if an IO error arises. In case the entity input stream is empty
     *                             and the reader is not able to produce a Java representation for
     *                             a zero-length entity, {@code NoContentException} is expected to
     *                             be thrown.
     * @throws javax.ws.rs.WebApplicationException
     *                             if a specific HTTP error response needs to be produced.
     *                             Only effective if thrown prior to the response being committed.
     */
    public T readFrom(Class<T> type, Type genericType,
                      Annotation[] annotations, MediaType mediaType,
                      MultivaluedMap<String, String> httpHeaders,
                      InputStream entityStream) throws java.io.IOException, javax.ws.rs.WebApplicationException;
}