yves amsellem yves amsellem - 15 days ago 6
Java Question

Jersey can produce List<T> but cannot Response.ok(List<T>).build()?

Jersey 1.6 can produce:

@Path("/stock")
public class StockResource {
@GET
@Produces(MediaType.APPLICATION_JSON)
public List<Stock> get() {
Stock stock = new Stock();
stock.setQuantity(3);
return Lists.newArrayList(stock);
}
}


But cannot do the same with:

@Path("/stock")
public class StockResource {
@GET
@Produces(MediaType.APPLICATION_JSON)
public Response get() {
Stock stock = new Stock();
stock.setQuantity(3);
return Response.ok(Lists.newArrayList(stock)).build();
}
}


Giving the error:
A message body writer for Java class java.util.ArrayList, and Java type class java.util.ArrayList, and MIME media type application/json was not found


This prevent the use of HTTP status code and headers.

Answer

It is possible to embed a List<T> in a Response the following way:

@Path("/stock")
public class StockResource {
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response get() {
        Stock stock = new Stock();
        stock.setQuantity(3);

        GenericEntity<List<Stock>> entity = 
            new GenericEntity<List<Stock>>(Lists.newArrayList(stock)) {};
        return Response.ok(entity).build();
    }
}

The client have to use the following lines to get the List<T>:

public List<Stock> getStockList() {
    WebResource resource = Client.create().resource(server.uri());
    ClientResponse clientResponse =
        resource.path("stock")
        .type(MediaType.APPLICATION_JSON)
        .get(ClientResponse.class);
    return clientResponse.getEntity(new GenericType<List<Stock>>() {
    });
}
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