JAX-RS uses implementations of MessageBodyReader and MessageBodyWriter to serialize/deserialize to and from differen media types. You can read more at JAX-RS Entity Providers. You can write your own to handle the serializion/derialization of your protobuf objects. Then just register the provider(s) with the application, either explicitly or implicitly through discovery.
Example
widgets.proto
package widget;
option java_package = "protobuf.example";
option java_outer_classname = "WidgetsProtoc";
message Widget {
required string id = 1;
required string name = 2;
}
message WidgetList {
repeated Widget widget = 1;
}
When this is compiled, I will be left with a WidgetsProtoc class with static inner Widget and WidgetList classes.
WidgetResource
import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
import protobuf.example.WidgetsProtoc.Widget;
import protobuf.example.WidgetsProtoc.WidgetList;
@Path("/widgets")
public class WidgetResource {
@GET
@Produces("application/protobuf")
public Response getAllWidgets() {
Widget widget1 =
Widget.newBuilder().setId("1").setName("widget 1").build();
Widget widget2 =
Widget.newBuilder().setId("2").setName("widget 2").build();
WidgetList list = WidgetList.newBuilder()
.addWidget(widget1).addWidget(widget2).build();
return Response.ok(list).build();
}
@POST
@Consumes("application/protobuf")
public Response postAWidget(Widget widget) {
StringBuilder builder = new StringBuilder("Saving Widget \n");
builder.append("ID: ").append(widget.getId()).append("\n");
builder.append("Name: ").append(widget.getName()).append("\n");
return Response.created(null).entity(builder.toString()).build();
}
}
You'll notice the use of the "application/protobuf" media type. This isn't a standard media type, but there is a draft in the working. Also the Guava library has define this media type as MediaType.PROTOBUF, which translates to "application/protobuf", so I chose to stick with that.
MessageBodyReader and MessageBodyWriter all defined in one class. You can choose to do it separately. Makes no difference.
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import javax.ws.rs.BadRequestException;
import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import protobuf.example.WidgetsProtoc.Widget;
import protobuf.example.WidgetsProtoc.WidgetList;
@Provider
@Produces("application/protobuf")
@Consumes("application/protobuf")
public class WidgetProtocMessageBodyProvider
implements MessageBodyReader, MessageBodyWriter {
@Override
public boolean isReadable(Class type, Type type1,
Annotation[] antns, MediaType mt) {
return Widget.class.isAssignableFrom(type)
|| WidgetList.class.isAssignableFrom(type);
}
@Override
public Object readFrom(Class type, Type type1, Annotation[] antns,
MediaType mt, MultivaluedMap mm, InputStream in)
throws IOException, WebApplicationException {
if (Widget.class.isAssignableFrom(type)) {
return Widget.parseFrom(in);
} else if (WidgetList.class.isAssignableFrom(type)) {
return WidgetList.parseFrom(in);
} else {
throw new BadRequestException("Can't Deserailize");
}
}
@Override
public boolean isWriteable(Class type, Type type1,
Annotation[] antns, MediaType mt) {
return Widget.class.isAssignableFrom(type)
|| WidgetList.class.isAssignableFrom(type);
}
@Override
public long getSize(Object t, Class type, Type type1,
Annotation[] antns, MediaType mt) { return -1; }
@Override
public void writeTo(Object t, Class type, Type type1,
Annotation[] antns, MediaType mt,
MultivaluedMap mm, OutputStream out)
throws IOException, WebApplicationException {
if (t instanceof Widget) {
Widget widget = (Widget)t;
widget.writeTo(out);
} else if (t instanceof WidgetList) {
WidgetList list = (WidgetList)t;
list.writeTo(out);
}
}
}
TestCase (Make sure the provider is registered both with the server and client)
@Test
public void testGetIt() {
Client client = ClientBuilder.newClient();
WebTarget target = client.target("http://localhost:8080/api");
// Get all list
WidgetList list = target.path("/widgets").request().get(WidgetList.class);
System.out.println("===== Response from GET =====");
for (Widget widget: list.getWidgetList()) {
System.out.println("id: " + widget.getId()
+ ", name: " + widget.getName());
}
// Post one
Widget widget = Widget.newBuilder().setId("10")
.setName("widget 10").build();
Response responseFromPost = target.path("widgets").request()
.post(Entity.entity(widget, "application/protobuf"));
System.out.println("===== Response from POST =====");
System.out.println(responseFromPost.readEntity(String.class));
responseFromPost.close();
}
Result:
===== Response from GET =====
id: 1, name: widget 1
id: 2, name: widget 2
===== Response from POST =====
Saving Widget
ID: 10
Name: widget 10
