Chapter 15. JAX-RS Content Negotiation

The HTTP protocol has built-in content negotiation headers that allow the client and server to specify the type of content that they transfer, and the type of content they prefer to receive. The server declares content preferences via the @Produces and @Consumes headers.

@Consumes is an array of media types that a particular resource or resource method consumes. For example:

         @Consumes("text/*")
         @Path("/library")
         public class Library {

         @POST
         public String stringBook(String book) {...}


         @Consumes("text/xml")
         @POST
         public String jaxbBook(Book book) {...}

         @Consumes("text/*")
         @Path("/library")
         public class Library {

         @POST
         public String stringBook(String book) {...}


         @Consumes("text/xml")
         @POST
         public String jaxbBook(Book book) {...}

Copy to Clipboard

Toggle word wrap

When a client makes a request, JAX-RS first locates all methods that match the path. It then sorts objects based on the content-type header sent by the client. If a client sends the following:

         POST /library
         content-type: text/plain

         this is a nice book

         POST /library
         content-type: text/plain

         this is a nice book

Copy to Clipboard

Toggle word wrap

The stringBook() method is invoked, because it matches the default text/* media type. If the client sends XML, like so:

         POST /library
         content-type: text/xml

         <book name="EJB 3.0" author="Bill Burke"/>

         POST /library
         content-type: text/xml

         <book name="EJB 3.0" author="Bill Burke"/>

Copy to Clipboard

Toggle word wrap

Then the jaxbBook() method is invoked.

@Produces is used to map a client request and match it with the client's Accept header. The Accept HTTP header is sent by the client, and defines the media types that the client prefers to receive from the server.

         @Produces("text/*")
         @Path("/library")
         public class Library {

         @GET
         @Produces("application/json")
         public String getJSON() {...}


         @GET
         public String get() {...}

         @Produces("text/*")
         @Path("/library")
         public class Library {

         @GET
         @Produces("application/json")
         public String getJSON() {...}


         @GET
         public String get() {...}

Copy to Clipboard

Toggle word wrap

So, if the client sends:

      
         GET /library
         Accept: application/json

      
         GET /library
         Accept: application/json

Copy to Clipboard

Toggle word wrap

The getJSON() method would be invoked.

@Consumes and @Produces can support multiple media types by presenting them in a list. The client's Accept header can also list multiple media types to receive. More specific media types are selected first. The Accept header (or @Produces or @Consumes) can also specify weighted preferences that will match requests with resource methods. (This is best explained in Section 14.1 of RFC 2616.) RESTEasy provides support for this more complex method of content negotiation.

An alternative method used by JAX-RS is a combination of media-type, content-language, and content encoding, in addition to etags, last modified headers, and other pre-conditions. This is a more complex form of content negotiation, performed programmatically by the application developer via the javax.ws.rs.Variant, VarianListBuilder, and Request objects. Request is injected using the @Context annotation. (For more information, read the JavaDoc.)

トップに戻る

このコンテンツは選択した言語では利用できません。

Chapter 15. JAX-RS Content Negotiation

詳細情報

試用、購入および販売

コミュニティー

Red Hat ドキュメントについて

多様性を受け入れるオープンソースの強化

会社概要

Theme

Red Hat legal and privacy links

Red Hat legal and privacy links