jakarta.ws.rs.ext

Interface MessageBodyReader<T>

Type Parameters:

T - Java type supported by the provider

public interface MessageBodyReader<T>

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. The MessageBodyReader pipeline is executed if the matching resource method declares an entity parameter or uses at least one FormParam.

Providers implementing MessageBodyReader contract must be either programmatically registered in a JAX-RS runtime or must be annotated with @Provider annotation to be automatically discovered by the JAX-RS runtime during a provider scanning phase.

Since:

1.0

Author:

Paul Sandoz, Marc Hadley

See Also:

Provider, Consumes

Method Summary

Modifier and Type	Method and Description
boolean	isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) Ascertain if the MessageBodyReader can produce an instance of a particular type.
T	readFrom(Class<T> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String,String> httpHeaders, InputStream entityStream) Read a type from the InputStream.

Method Detail

isReadable

boolean isReadable(Class<?> type,
                   Type genericType,
                   Annotation[] annotations,
                   MediaType mediaType)

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.

Parameters:

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.

readFrom

T readFrom(Class<T> type,
           Type genericType,
           Annotation[] annotations,
           MediaType mediaType,
           MultivaluedMap<String,String> httpHeaders,
           InputStream entityStream)
    throws IOException,
           WebApplicationException

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 JAX-RS server runtime into a BadRequestException wrapping the original NoContentException and rethrown for a standard processing by the registered exception mappers.

Parameters:

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.

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.

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.