Question

I have a JAX-RS resource, which gets its paramaters as a JSON string like this:

http://some.test/aresource?query={"paramA":"value1", "paramB":"value2"}

The reason to use JSON here, is that the query object can be quite complex in real use cases.

I’d like to convert the JSON string to a Java object, dto in the example:

@GET 
@Produces("text/plain")
public String getIt(@QueryParam("query") DataTransferObject dto ) {
    ...
}

Does JAX-RS support such a conversion from JSON passed as a query param to Java objects?

Answer 1

Yes, you can do this, but you will need to write the conversion code yourself. Fortunately, this is easy, you just need to write a class that has a public String constructor to do the conversion. For example:

public class JSONParam {
    private DataTransferObject dto;

    public JSONParam(String json) throws WebApplicationException {
        try {
            // convert json string DataTransferObject and set dto
        }
        catch (JSONException e) {
            throw new WebApplicationException(Response.status(Status.BAD_REQUEST)
                    .entity("Couldn't parse JSON string: " + e.getMessage())
                    .build());
        }
    }

    public DataTransferObject getDTO() {
        return dto;
    }
}

Then you can use:

@GET 
@Produces("text/plain")
public String getIt(@QueryParam("query") JSONParam json) {
    DataTransferObject dto = json.getDTO();
    ...
}