sparql update on FusekiEmbeddedServer

[Erich Bremer]

I'm trying to do a "insert data {}" command on the following end-point for
FusekiEmbeddedServer.

        DataService dataService = new DataService(ds.asDatasetGraph());
        dataService.addEndpoint(OperationName.Quads_RW, "");
        dataService.addEndpoint(OperationName.Query, "");
        dataService.addEndpoint(OperationName.Update, "");
        FusekiEmbeddedServer fs = FusekiEmbeddedServer.create()
            .setPort(8888)
            .add("/ds", dataService)
            .build();
        fs.start();

I get an error of:

Error 400: Parse error:
prefix : <http://www.ebremer.com/pred/>
insert data {<http://www.ebremer.com/test123> :name "Erich Bremer"}

Encountered " <INSERT_DATA> "insert data "" at line 2, column 1.
Was expecting one of:
    "base" ...
    "prefix" ...
    "select" ...
    "describe" ...
    "construct" ...
    "ask" ...


What am I doing wrong or not understanding?  - Erich