Java Reference
In-Depth Information
The difference is that the @Consumes annotation is used instead of the @Produces annotation
to correlate media types.
Let's now look at how we read and convert our HTTP message into a Java object:
Object readFrom ( Class < Object >, Type genericType ,
Annotation annotations [], MediaType mediaType ,
MultivaluedMap < String , String > httpHeaders ,
InputStream entityStream )
throws IOException , WebApplicationException {
try {
JAXBContext ctx = JAXBContext . newInstance ( type );
return ctx . createUnmarshaller (). unmarshal ( entityStream );
} catch
catch ( JAXBException ex ) {
throw new
new RuntimeException ( ex );
The readFrom() method gives us access to the HTTP headers of the incoming request as
well as a that represents the request message body. Here, we just cre-
ate a JAXBContext based on the Java type we want to create and use a
javax.xml.bind.Unmarshaller to extract it from the stream.
Life Cycle and Environment
By default, only one instance of each MessageBodyReader , MessageBodyWriter , or Con-
textResolver is created per application. If JAX-RS is allocating instances of these compon-
ents (see Chapter 14 ), the classes of these components must provide a public constructor for
which the JAX-RS runtime can provide all the parameter values. A public constructor may
only include parameters annotated with the @Context annotation. For example:
@Consumes ( "application/json" )
public class
class MyJsonReader
MyJsonReader implements
implements MessageBodyReader {
public MyJsonReader ( @Context Providers providers ) {
this . providers = providers ;
Whether or not the JAX-RS runtime is allocating the component instance, JAX-RS will per-
form injection into properly annotated fields and setter methods. Again, you can only inject
JAX-RS objects that are found using the @Context annotation.
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