7.1.7 Bind Errors

Often you want to consume an endpoint and bind to a POJO if the request is successful and bind to a different POJO if an error occurs. The following example shows how to invoke exchange with a success and error type.

@Controller("/books")
public class BooksController {
    @Get("/{isbn}")
    public HttpResponse find(String isbn) {
        if (isbn.equals("1680502395")) {
            Map<String, Object> m = new HashMap<>();
            m.put("status", 401);
            m.put("error", "Unauthorized");
            m.put("message", "No message available");
            m.put("path", "/books/" + isbn);
            return HttpResponse.status(HttpStatus.UNAUTHORIZED).body(m);
        }
        return HttpResponse.ok(new Book("1491950358", "Building Microservices"));
    }
}

@Controller("/books")
class BooksController {
    @Get("/{isbn}")
    HttpResponse find(String isbn) {
        if (isbn == "1680502395") {
            Map<String, Object> m = [
                    status : 401,
                    error  : "Unauthorized",
                    message: "No message available",
                    path   : "/books/" + isbn]
            return HttpResponse.status(HttpStatus.UNAUTHORIZED).body(m)
        }
        return HttpResponse.ok(new Book("1491950358", "Building Microservices"))
    }
}

@Controller("/books")
class BooksController {
    @Get("/{isbn}")
    fun find(isbn: String): HttpResponse<*> {
        if (isbn == "1680502395") {
            val m = mapOf(
                "status" to 401,
                "error" to "Unauthorized",
                "message" to "No message available",
                "path" to "/books/$isbn"
            )
            return HttpResponse.status<Any>(HttpStatus.UNAUTHORIZED).body(m)
        }
        return HttpResponse.ok(Book("1491950358", "Building Microservices"))
    }
}

    @Test
    public void afterAnHttpClientExceptionTheResponseBodyCanBeBoundToAPOJO() {
        try {
            client.toBlocking().exchange(HttpRequest.GET("/books/1680502395"),
                    Argument.of(Book.class), (1)
                    Argument.of(CustomError.class)); (2)
        } catch (HttpClientResponseException e) {
            assertEquals(HttpStatus.UNAUTHORIZED, e.getResponse().getStatus());
            Optional<CustomError> jsonError = e.getResponse().getBody(CustomError.class);
            assertTrue(jsonError.isPresent());
            assertEquals(401, jsonError.get().status);
            assertEquals("Unauthorized", jsonError.get().error);
            assertEquals("No message available", jsonError.get().message);
            assertEquals("/books/1680502395", jsonError.get().path);
        }
    }

    def "after an HttpClientException the response body can be bound to a POJO"() {
        when:
        client.toBlocking().exchange(HttpRequest.GET("/books/1680502395"),
                Argument.of(Book), (1)
                Argument.of(CustomError)) (2)
        then:
        def e = thrown(HttpClientResponseException)
        e.response.status == HttpStatus.UNAUTHORIZED
        when:
        Optional<CustomError> jsonError = e.response.getBody(CustomError)
        then:
        jsonError.isPresent()
        jsonError.get().status == 401
        jsonError.get().error == 'Unauthorized'
        jsonError.get().message == 'No message available'
        jsonError.get().path == '/books/1680502395'
    }

        "after an httpclient exception the response body can be bound to a POJO" {
            try {
                client.toBlocking().exchange(HttpRequest.GET<Any>("/books/1680502395"),
                        Argument.of(Book::class.java), (1)
                        Argument.of(CustomError::class.java)) (2)
            } catch (e: HttpClientResponseException) {
                e.response.status shouldBe HttpStatus.UNAUTHORIZED
            }
        }