Rest Assured: Why do I get IllegalStateException exception?

Question

I am in the process of studying Rest-Assured framework.

I am using http://ziptasticapi.com free API for my drills.

When I call:

final static String BASE_URI = "http://ziptasticapi.com/";

final static String ADAK_ZIP_CODE = "99546"; //{"country":"US","state":"AK","city":"ADAK"}
final static String ATKA_ZIP_CODE = "99547";

public static final String GET_METHOD = "GET";
    RestAssured.baseURI = BASE_URI;

    String responseString = when().get(ADAK_ZIP_CODE).then()
            .statusCode(200)
            .and()
            .extract()
            .asString();

    System.out.println(responseString);

I get the following string:

{"country":"US","state":"AK","city":"ADAK"}

as responseString value.

When I am trying:

 RestAssured.baseURI = BASE_URI;      

 ZipData zipdata = when().get(ADAK_ZIP_CODE).then()
            .statusCode(200)
            .and()
            .extract()
            .as(ZipData.class);

public class ZipData {

    public String country;
    public String state;
    public String city;

}

I crash on :

java.lang.IllegalStateException: Cannot parse object because no supported Content-Type was specified in response. Content-Type was 'text/html;charset=UTF-8'.

Why is that? Could it be the rest returns an Html and not Json? How do I handle this?

Thanks!

Answer 1

First of all, keep in mind that REST Assured is a HTTP client primarily designed for testing HTTP APIs. So let me highlight that you shouldn't use REST Assured for anything other than testing.

---

Looks like the endpoint you are attempting to consume is returning a JSON document in the response payload, but the value of the Content-Type header is text/html;charset=UTF-8, so REST Assured cannot parse the response as a JSON document and convert it to an instance of ZipData. That's not what you expect from a sound HTTP API.

You could work around it and write a filter to override the Content-Type header, as show below:

public class OverrideContentTypeFilter implements Filter {

    @Override
    public Response filter(FilterableRequestSpecification requestSpec,
                           FilterableResponseSpecification responseSpec,
                           FilterContext ctx) {

        Response next = ctx.next(requestSpec, responseSpec);
        return new ResponseBuilder().clone(next).setContentType(ContentType.JSON).build();
    }
}

Then use it as follows:

ZipData zipdata =
        given()
            .filter(new OverrideContentTypeFilter())
        .when()
            .get(uri)
        .then()
            .statusCode(200)
            .extract()
            .as(ZipData.class);