Mockito is returning "java.lang.IllegalArgumentException: URI is not absolute" in RestTemplate.exchange Springboot - spring-boot

Question

Mockito is returning "java.lang.IllegalArgumentException: URI is not absolute" in RestTemplate.exchange. I am not sure why this is happening because it seems I am mocking the restTemplate properly and since I am seeing that exception, it seems that RestTemplate is not a mock.
Here is my class
#Component
public class RestTemplateWrapper {
private static final Logger LOGGER = LoggerFactory.getLogger(RestTemplateWrapper.class);
public <T> ResponseEntity<T> callWebServiceGET(String url,HttpEntity<?> httpEntity,
ParameterizedTypeReference<T> parameterizedTypeReference) {
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<T> response=null;
LOGGER.trace("Entered callWebServiceGET");
LOGGER.info("Calling WebService {}", url);
try {
response=restTemplate.exchange(url, HttpMethod.GET, httpEntity, parameterizedTypeReference);
} catch (HttpClientErrorException e) {
if (HttpStatus.NOT_FOUND.equals(e.getStatusCode())) {
LOGGER.error("Service Unavailable - Code 404 returned. " + url + e.getMessage());
} else if (HttpStatus.UNAUTHORIZED.equals(e.getStatusCode())) {
LOGGER.error("Token Expired- Code 401 returned. " + e.getMessage());
} else if (HttpStatus.BAD_REQUEST.equals(e.getStatusCode())) {
LOGGER.error("Bad Input, 400 returned.{} {} ", url , e.getMessage(), e);
} else {
LOGGER.error("WEB Service Failure. " + e.getMessage());
}
}
return response;
}
}
And here is my TestCase:
#PrepareForTest({RestTemplateWrapper.class})
public class RestTemplateWrapperTest {
#Mock
private RestTemplate mockRestTemplate;
#InjectMocks
private RestTemplateWrapper webUtils;
#Before
public void setUp() throws Exception {
MockitoAnnotations.initMocks(this);
}
#Test
public void callWebServiceGET_OK() {
HttpEntity<String> httpEntity= new ResponseEntity<>(HttpStatus.OK);
ResponseEntity<String> entityResponse=new ResponseEntity<>("MOCK_RESPONSE", HttpStatus.OK);
when(mockRestTemplate.exchange(eq("/objects/get-objectA"), eq(HttpMethod.GET), eq(httpEntity),any(
ParameterizedTypeReference.class))).thenReturn(
entityResponse);
ResponseEntity<String> mockResponse= webUtils.callWebServiceGET("",null, new ParameterizedTypeReference<String>(){
});
//verify(mockRestTemplate,times(1)).exchange(Matchers.anyString(), Matchers.any(), Matchers.any());
Assert.assertEquals("MOCK_RESPONSE",mockResponse.getBody());
}
}
The response:
URI is not absolute
java.lang.IllegalArgumentException: URI is not absolute
at java.net.URI.toURL(URI.java:1088)
at org.springframework.http.client.SimpleClientHttpRequestFactory.createRequest(SimpleClientHttpRequestFactory.java:145)
at org.springframework.http.client.support.HttpAccessor.createRequest(HttpAccessor.java:87)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:727)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:666)
at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:604)
at com.project.di.tp.purchaseorderservice.utils.RestTemplateWrapper.callWebServiceGET(RestTemplateWrapper.java:29)
at com.project.di.tp.purchaseorderservice.utils.RestTemplateWrapperTest.callWebServiceGET_OK(RestTemplateWrapperTest.java:51)
Any idea about how to solve this issue? I have been trying like 4 hours.

Answer 1

I found the solution, it seems the problem is that my class is RestTemplateWrapper is creating a instance inside callWebServiceGET therefore mockito can`t mock that object. If if set the object outside the method, it works but I dont want to do that.
Is there any way to mock a object that is inside a method?

Answer 2

Although it is not stated explicitly in the JavaDocs it is the case that you have to provide an absolute URL there.
This is because you do nowhere provide a base URL where a relative URL would be relative to. You could not enter "/objects/get-objectA" as URL in your browser either.
So I would suggest that you use something like "http://example.com/objects/get-objectA" instead for the first parameter:
when(mockRestTemplate.exchange(
eq("http://example.com/bla"),
eq(HttpMethod.GET),
isNull(HttpEntity.class),
any(ParameterizedTypeReference.class))).
thenReturn(entityResponse);
ResponseEntity<String> mockResponse =
webUtils.callWebServiceGET(
"http://example.com/bla",
null,
new ParameterizedTypeReference<String>(){});
Please note that the call to webUtils.callWebServiceGET with given parameters would not make Mockito return the wanted answer, so I changed for one the URL in the call to the absolute URL you are expecting in the Mockito.when and also changed the parameter expected there to be a typed null (typed to match the method signature).
UPDATE:
As you found out by yourself already, your Mockito.when doesn't work because you do not use the created mock from the test in your tested method, but instead create a fresh instance of RestTemplate in each call of callWebServiceGET. (Don't know why I didn't see it earlier, sorry!)
I recommend that instead you inject the RestTemplate into the tested class with a constructor:
private final RestTemplate restTemplate;
public RestTemplateWrapper(RestTemplate restTemplate) {
this.restTemplate = restTemplate;
}
// remove the following line in the method callWebServiceGET:
// RestTemplate restTemplate = new RestTemplate();
With this code, Spring will automatically inject your mocked RestTemplate into the test, but for running the production code you need to add a bean to provide a RestTemplate for injection.
Add this to a Configuration class where you also define other beans:
#Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
// Do any additional configuration here
return builder.build();
}
(Found this code snippet in an answer to How to autowire RestTemplate using annotations)
And as a general advice for testing: try to avoid the use of the new operator in any code you want to test, but use injection instead. If you need to create multiple instances (e.g. in a loop, etc.) try to inject a factory that creates the instances for you - so in the test you can mock the factory.