16.3. Providers Utility Class

public interface Providers
{

   /**
    * Get a message body reader that matches a set of criteria. The set of
    * readers is first filtered by comparing the supplied value of
    * {@code mediaType} with the value of each reader's
    * {@link javax.ws.rs.Consumes}, ensuring the supplied value of
    * {@code type} is assignable to the generic type of the reader, and
    * eliminating those that do not match.
    * The list of matching readers is then ordered with those with the best
    * matching values of {@link javax.ws.rs.Consumes} (x/y > x/* > */*)
    * sorted first. Finally, the
    * {@link MessageBodyReader#isReadable}
    * method is called on each reader in order using the supplied criteria and
    * the first reader that returns {@code true} is selected and returned.
    *
    * @param type        the class of object that is to be written.
    * @param mediaType   the media type of the data that will be read.
    * @param genericType the type of object 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>Class.getGenericParameterTypes</code>.
    * @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>Class.getParameterAnnotations</code>.
    * @return a MessageBodyReader that matches the supplied criteria or null
    *         if none is found.
    */
   <T> MessageBodyReader<T> getMessageBodyReader(Class<T> type,
                                                 Type genericType, Annotation annotations[], MediaType mediaType);

   /**
    * Get a message body writer that matches a set of criteria. The set of
    * writers is first filtered by comparing the supplied value of
    * {@code mediaType} with the value of each writer's
    * {@link javax.ws.rs.Produces}, ensuring the supplied value of
    * {@code type} is assignable to the generic type of the reader, and
    * eliminating those that do not match.
    * The list of matching writers is then ordered with those with the best
    * matching values of {@link javax.ws.rs.Produces} (x/y > x/* > */*)
    * sorted first. Finally, the
    * {@link MessageBodyWriter#isWriteable}
    * method is called on each writer in order using the supplied criteria and
    * the first writer that returns {@code true} is selected and returned.
    *
    * @param mediaType   the media type of the data that will be written.
    * @param type        the class of object that is to be written.
    * @param genericType the type of object to be written. E.g. if the
    *                    message body is to be produced from a field, this will be
    *                    the declared type of the field as returned by
    *                    <code>Field.getGenericType</code>.
    * @param annotations an array of the annotations on the declaration of the
    *                    artifact that will be written. E.g. if the
    *                    message body is to be produced from a field, this will be
    *                    the annotations on that field returned by
    *                    <code>Field.getDeclaredAnnotations</code>.
    * @return a MessageBodyReader that matches the supplied criteria or null
    *         if none is found.
    */
   <T> MessageBodyWriter<T> getMessageBodyWriter(Class<T> type,
                                                 Type genericType, Annotation annotations[], MediaType mediaType);

   /**
    * Get an exception mapping provider for a particular class of exception.
    * Returns the provider whose generic type is the nearest superclass of
    * {@code type}.
    *
    * @param type the class of exception
    * @return an {@link ExceptionMapper} for the supplied type or null if none
    *         is found.
    */
   <T extends Throwable> ExceptionMapper<T> getExceptionMapper(Class<T> type);

   /**
    * Get a context resolver for a particular type of context and media type.
    * The set of resolvers is first filtered by comparing the supplied value of
    * {@code mediaType} with the value of each resolver's
    * {@link javax.ws.rs.Produces}, ensuring the generic type of the context
    * resolver is assignable to the supplied value of {@code contextType}, and
    * eliminating those that do not match. If only one resolver matches the
    * criteria then it is returned. If more than one resolver matches then the
    * list of matching resolvers is ordered with those with the best
    * matching values of {@link javax.ws.rs.Produces} (x/y > x/* > */*)
    * sorted first. A proxy is returned that delegates calls to
    * {@link ContextResolver#getContext(java.lang.Class)} to each matching context
    * resolver in order and returns the first non-null value it obtains or null
    * if all matching context resolvers return null.
    *
    * @param contextType the class of context desired
    * @param mediaType   the media type of data for which a context is required.
    * @return a matching context resolver instance or null if no matching
    *         context providers are found.
    */
   <T> ContextResolver<T> getContextResolver(Class<T> contextType,
                                             MediaType mediaType);
}

public interface Providers
{

   /**
    * Get a message body reader that matches a set of criteria. The set of
    * readers is first filtered by comparing the supplied value of
    * {@code mediaType} with the value of each reader's
    * {@link javax.ws.rs.Consumes}, ensuring the supplied value of
    * {@code type} is assignable to the generic type of the reader, and
    * eliminating those that do not match.
    * The list of matching readers is then ordered with those with the best
    * matching values of {@link javax.ws.rs.Consumes} (x/y > x/* > */*)
    * sorted first. Finally, the
    * {@link MessageBodyReader#isReadable}
    * method is called on each reader in order using the supplied criteria and
    * the first reader that returns {@code true} is selected and returned.
    *
    * @param type        the class of object that is to be written.
    * @param mediaType   the media type of the data that will be read.
    * @param genericType the type of object 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>Class.getGenericParameterTypes</code>.
    * @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>Class.getParameterAnnotations</code>.
    * @return a MessageBodyReader that matches the supplied criteria or null
    *         if none is found.
    */
   <T> MessageBodyReader<T> getMessageBodyReader(Class<T> type,
                                                 Type genericType, Annotation annotations[], MediaType mediaType);

   /**
    * Get a message body writer that matches a set of criteria. The set of
    * writers is first filtered by comparing the supplied value of
    * {@code mediaType} with the value of each writer's
    * {@link javax.ws.rs.Produces}, ensuring the supplied value of
    * {@code type} is assignable to the generic type of the reader, and
    * eliminating those that do not match.
    * The list of matching writers is then ordered with those with the best
    * matching values of {@link javax.ws.rs.Produces} (x/y > x/* > */*)
    * sorted first. Finally, the
    * {@link MessageBodyWriter#isWriteable}
    * method is called on each writer in order using the supplied criteria and
    * the first writer that returns {@code true} is selected and returned.
    *
    * @param mediaType   the media type of the data that will be written.
    * @param type        the class of object that is to be written.
    * @param genericType the type of object to be written. E.g. if the
    *                    message body is to be produced from a field, this will be
    *                    the declared type of the field as returned by
    *                    <code>Field.getGenericType</code>.
    * @param annotations an array of the annotations on the declaration of the
    *                    artifact that will be written. E.g. if the
    *                    message body is to be produced from a field, this will be
    *                    the annotations on that field returned by
    *                    <code>Field.getDeclaredAnnotations</code>.
    * @return a MessageBodyReader that matches the supplied criteria or null
    *         if none is found.
    */
   <T> MessageBodyWriter<T> getMessageBodyWriter(Class<T> type,
                                                 Type genericType, Annotation annotations[], MediaType mediaType);

   /**
    * Get an exception mapping provider for a particular class of exception.
    * Returns the provider whose generic type is the nearest superclass of
    * {@code type}.
    *
    * @param type the class of exception
    * @return an {@link ExceptionMapper} for the supplied type or null if none
    *         is found.
    */
   <T extends Throwable> ExceptionMapper<T> getExceptionMapper(Class<T> type);

   /**
    * Get a context resolver for a particular type of context and media type.
    * The set of resolvers is first filtered by comparing the supplied value of
    * {@code mediaType} with the value of each resolver's
    * {@link javax.ws.rs.Produces}, ensuring the generic type of the context
    * resolver is assignable to the supplied value of {@code contextType}, and
    * eliminating those that do not match. If only one resolver matches the
    * criteria then it is returned. If more than one resolver matches then the
    * list of matching resolvers is ordered with those with the best
    * matching values of {@link javax.ws.rs.Produces} (x/y > x/* > */*)
    * sorted first. A proxy is returned that delegates calls to
    * {@link ContextResolver#getContext(java.lang.Class)} to each matching context
    * resolver in order and returns the first non-null value it obtains or null
    * if all matching context resolvers return null.
    *
    * @param contextType the class of context desired
    * @param mediaType   the media type of data for which a context is required.
    * @return a matching context resolver instance or null if no matching
    *         context providers are found.
    */
   <T> ContextResolver<T> getContextResolver(Class<T> contextType,
                                             MediaType mediaType);
}

            @Provider
            @Consumes("multipart/fixed")
            public class MultipartProvider implements MessageBodyReader {

            private @Context Providers providers;

            ...

            }

            @Provider
            @Consumes("multipart/fixed")
            public class MultipartProvider implements MessageBodyReader {

            private @Context Providers providers;

            ...

            }