Avoiding a NPE when checking JSON response using JsonPath and Rest Assured

Question

Given the following JSON:

{
 "priceOne": 1034,
 "priceTwo": null,
 "priceThree": 7282,
}

...and the following Rest Assured method to get the priceTwo value and set to a specific value:

public void getPrice() {
 setPriceService();
 Response response =
 given().
 spec(priceServiceRequestSpec)
 when().
 get("api/v1/prices/102934").
 then().extract().response();
 if (StringUtils.isNotEmpty(response.path("priceTwo").toString())) {
 vehicle.setPrice(response.path("priceTwo").toString());
 return true;
 } else {
 vehicle.setPrice("2000");
 }
}

...I am getting a NullPointerException when I expect the StringUtils.isNotEmpty to handle this. I expect this is down to the way I am using the response.path as a paramater. What is a better way of achieving this?

• João Farias: If you are receiving this JSON object, you should never have an NPE. Are you sure "priceTwo" exists? If it doesn't, you will get the NPE on the .toString(), no on StringUtils.isNotEmpty().
• Steerpike: @JoãoFarias thanks, I think this makes sense. Problem is, I never know which price will be null, so I wanted a better way of doing a null check without lots of boilerplate try/catch NPE code. Any of the prices can be null (not a string "null") and I need to set a value IF they are null
• Steerpike: I think this is perhaps the right approach: jvt.me/posts/2019/04/23/rest-assured-verify-field-not-set

Answer 1

String response =RestAssured.get("https://praveendvd.free.beeceptor.com/test").
 then().extract().response().asString();
 
JSONObject jsonObj = new JSONObject(response);
 
int val = (jsonObj.isNull("priceTwo")) ? 2:jsonObj.get("priceTwo");
vehicle.setPrice(val);

you can directly pass without creating a variable also:

vehicle.setPrice((jsonObj.isNull("priceTwo")) ? 2:jsonObj.get("priceTwo"));

use JsonObject has method and ternary operator java

• Steerpike: thanks for the answer - this looks the neatest solution yet the jsonObj.has always evaluates to true, because priceTwo key always exists, regardless of whether value is null, so the l/h side of ? always gets run with the result: org.json.JSONObject$Null cannot be cast to java.lang.Integer java.lang.ClassCastException: org.json.JSONObject$Null cannot be cast to java.lang.Integer
• PDHide: @Steerpike use jsonObj.isNull("species") then , i thought you want to validate whether key exists or not
• Steerpike: apologies, I probably wasn't clear. I want to perform conditional logic IF a value is null. So, I want to send a new Update RQ if any of the key values are null e.g. if "priceTwo": null
• PDHide: @Steerpike is updated answer

Answer 2

Response response =RestAssured.get("https://praveendvd.free.beeceptor.com/test").
 then().extract();
if (StringUtils.isNotEmpty(response.path("priceTwo").toString())) {
 vehicle.setPrice(response.path("priceTwo").toString());
 return true;
} else {
 vehicle.setPrice("2000");
}

You should creating a variable and also most probablity, you have a type casting problem that Response type to convert String for condition.

Answer 3

Since the path returns a reference type you can just use the construction like this:

if (response.path("priceTwo") instanceof Number) {
 vehicle.setPrice(response.path("priceTwo").toString());
 return true;
} else {
 vehicle.setPrice("2000");
}

Below is the test:

public class Test {
 public static void main(String[] args) {
 Response response = RestAssured
 .get("https://60269516186b4a0017780505.mockapi.io/rest_assured_nulls");
 handleJson(response, "[0].priceOne");
 handleJson(response, "[0].priceTwo");
 handleJson(response, "asdfe");
 }
 private static void handleJson(Response response, String path){
 if (response.path(path) instanceof Number) {
 System.out.println("Valid number: " + response.path(path).toString());
 } else {
 System.out.println("Invalid number so setting default value");
 }
 }
}

which outputs:

Valid number: 1034
Invalid number so setting default value
Invalid number so setting default value

for my test endpoint

• PDHide: if response doesn't have priceTwo it will throw null point , that was the question i guess
• Alexey R.: No, it will not. null instanceof Number will return false
• PDHide: response.path("priceTwo") will through the error
• PDHide: response.path("asdasd") try this it will throw nullpoint
• Alexey R.: Not sure why we're talking about response.path("asdasd"). OP's issue is that "priceTwo": null causes .toString() be invoked against null reference because the value of the field is null. I'll check your examples as soon as get to my desktop.