I'm having a hard time figuring out how to mock a KafkaConsumer. Below is the basic structure of my code.
public void run() {
...
try (KafkaConsumer<String, String> consumer = new KafkaConsumer<>(kafkaParams)) {
consumer.subscribe(topic);
ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(pollInterval));
methodToProcessRecords();
...
}
}
I want to do something like this:
whenCreateNewConsumer().thenReturn(mockConsumer);
when(mockConsumer.poll()).thenReturn(mockConsumerRecords);
I'm having a hard time figuring out how to mock a KafkaConsumer
Use MockConsumer
Alternatively, it's not really clear what you are consuming from. If you want to produce and consume, use Kafka Streams TopologyTestDriver
First change your class (to be tested) variable type to use Consumer Interface instead of Class. instead of using KafkaConsumer. use this Consumer interface
there should not be any code change needed, just variable type change.
(same applies to producer also)
Now in your unit test class
private MockConsumer<String, String> mockConsumer = new MockConsumer<>(OffsetResetStrategy.EARLIEST);
now you can assign the above variable to your class which you are trying to unit test
If your consumer is public, its very easy to set. If its private variable, you can use reflection
ToBeTested class = new ToBeTested();
Field field = class.getClass().getDeclaredField("privateVariableNameOfKafkaConsumer");
field.setAccessible(true);
field.set("class", mockConsumer);
Related
I Have a class for which i want to write a Junit unit test case.
public class ComparatorUtil {
public static Map<String, ValueDifference<Object>> compareJsonObject(Object srcObject, Object targetObject)
throws JsonGenerationException, JsonMappingException, IOException {
String initialJson = ConverterUtil.convertObjectToJson(srcObject);
String updatedJson = ConverterUtil.convertObjectToJson(targetObject);
Gson g = new Gson();
Type mapType = new TypeToken<Map<String, Object>>(){}.getType();
Map<String, Object> firstMap = g.fromJson(initialJson, mapType);
Map<String, Object> secondMap = g.fromJson(updatedJson, mapType);
Map<String, MapDifference.ValueDifference<Object>> diffMap = Maps.difference(firstMap, secondMap).entriesDiffering();
return diffMap;
}
}
public class ConverterUtil {
public static String convertObjectToJson(Object o)
throws JsonGenerationException, JsonMappingException, IOException {
ObjectMapper mapperObj = new ObjectMapper();
return mapperObj.writeValueAsString(o);
}
}
Junit test case written by me:-
#RunWith(PowerMockRunner.class)
#PrepareForTest(ConverterUtil.class)
public class ComparatorUtilTest {
#Before
public void setUp() {
PowerMockito.mockStatic(ConverterUtil.class);
}
#Test
public void testValueDiff() throws JsonGenerationException, JsonMappingException, IOException {
TestObject srcObject = new TestObject();
srcObject.setColor("white");
srcObject.setId(1);
TestObject targetObj = new TestObject();
targetObj.setColor("white");
targetObj.setId(1);
targetObj.setSuffix("AA");
ComparatorUtil.compareJsonObject(srcObject, targetObj);
PowerMockito.verifyStatic(VerificationModeFactory.times(2));
ConverterUtil.convertObjectToJson(srcObject);
ConverterUtil.convertObjectToJson(targetObj);
}
}
When I am running the test class, I am getting a Null Pointer Exception as the initialJson and updatedJson is coming to be null. Can anyone please tell me where am I doing wrong?
So many things so wrong here.
You seem to assume how to use PowerMock. But what you put together simply doesn't make sense! You need to create a mocking specification using 'when().thenReturn()' for example.
Meaning: it is not enough to instruct PowerMock that a certain class will be mocked. You have to tell PowerMock about the actual values to be returned when these static methods are invoked.
so start by reading a good tutorial top to bottom. Don't use PowerMock for your own code, instead look how a tutorial solves a simple problem.
Then: PowerMock comes at certain cost. So you avoid using it. You rather should step back and look into reworking your code so that it can be tested without the need to mock static methods. You see, we are talking about code that transforms some input into some output. You should be able to write production and test code that requires no mocking at all for such situations. If at all, you should use frameworks such as Mockito - good production code can be tested without PowerMock.
More specifically: why is there a need to mock the static method? That seems to indicate that your ObjectMapper doesn't work in your unit test setup. It starts right there!
You see, a good unit test for your conversion method should simply look like:
assertThat(someConverterUnderTest.convert(fineTunedInput), is(expectedOutput));
That's it! You should design your converter to fully work in your unit test environment. And then all need for mocks is gone. In other words: you are currently testing implementation details. Instead you should always try testing the public contract of your methods. Testing implementation details is sometimes unavoidable, but as written before: the code you are showing here should really really be tested without mocks.
Then: even when you need mocks: the static methods are getting in your way. That is a clear signal that you shouldn't be using static here! Instead, you turn those elements that might require mocking either into parameters or into fields of your classes under test. Because then you can simply inject mocked objects. Which means that you don't need the PowerMock(ito) tooling anymore.
I'm using a Calendar object to determine whether or not to increase the workload of a system based on current day/hour values. Given that this object uses static methods, I'm using PowerMock to mock the static methods with the following annotations:
#RunWith(PowerMockRunner.class)
#PrepareForTest({ Calendar.class })
The code under test is pretty simple (though my logic needs work, I know):
public void determineDefaultMaximumScans() throws ParseException{
parseTime();
Calendar cal = Calendar.getInstance();
int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
System.out.println(cal.get(Calendar.DAY_OF_WEEK));
if(dayOfWeek == (Calendar.SATURDAY) || dayOfWeek == (Calendar.SUNDAY)){
setDefaultMax(calculateNewDefaultMax(getDefaultMax()));
System.out.println("defaultMax increased by 20%");
} else {
if(currentTime.after(afterHoursBegin) && currentTime.before(afterHoursEnd)){
System.out.println("Not afterhours. Maintaining current maximum.");
setDefaultMax(defaultMax);
System.out.println("Current Maximum number of scans: " + getDefaultMax());
}
}
}
My test case reads as follows:
#SuppressWarnings("static-access")
#Test
public void testDetermineMaximumScans() throws ParseException{
PowerMock.mockStatic(Calendar.class);
String beginningTime = "18:00";
String endingTime = "05:00";
mockAfterHoursBegin = parser.parse(beginningTime);
mockAfterHoursEnd = parser.parse(endingTime);
mockCurrentTime = parser.parse(parser.format(new Date()));
EasyMock.expect(Calendar.getInstance()).andReturn(mockCalendar);
EasyMock.expect(mockCalendar.get(Calendar.DAY_OF_WEEK)).andReturn(6);
EasyMock.replay(mocks);
offHourMaximumCalculator.determineDefaultMaximumScans();
EasyMock.verify(mocks);
}
As of now, all of my attempts to return a specific value result in the following assertion error. Now I vaguely understand why it's returning the default but I do not see why I can't force the value or how to get around this expectation. Mocks in general are still a frustrating mystery to me. What am I missing?
java.lang.AssertionError:
Expectation failure on verify:
Calendar.get(7): expected: 1, actual: 0
Mocks are fairly simple. But wanting to mock static methods is a big running after complexity. I generally do not recommend to mock something like a Calendar. If you do weird and complex thing with it, just encapsulate in something you can test and mock easily.
And in fact, we pretty much never use Calendar.getInstance(). It returns something according to the locale. But it's rare that you don't want a specific calendar i.e. GregorianCalendar. So just do new GregorianCalendar.
But anyway, add a protected method doing
protected Calendar newCalendar() {
return Calendar.getInstance(); // or new GregorianCalendar()
}
will take 2 minutes and then a simple partial mock will do the trick.
Finally, I also don't recommend to use Calendar. You have a much nicer API in java.util.date in Java 8.
All this said, here is how you should do it. Calendar is a system class, so you need to follow a real specific path which is explained here.
#RunWith(PowerMockRunner.class)
#PrepareForTest(Calendar.class)
public class MyTest {
#Test
public void testDetermineMaximumScans() throws ParseException {
PowerMock.mockStatic(Calendar.class);
Calendar calendar = mock(Calendar.class);
EasyMock.expect(Calendar.getInstance()).andReturn(calendar);
EasyMock.expect(calendar.get(Calendar.DAY_OF_WEEK)).andReturn(6);
// really important to replayAll to replay the static expectation
PowerMock.replayAll(calendar);
assertThat(Calendar.getInstance().get(Calendar.DAY_OF_WEEK)).isEqualTo(6);
// and verifyAll is you want to verify that the static call actually happened
PowerMock.verifyAll();
}
}
I'm really stuck with cast Rabbit response to POJO. How to do it properly? On sprin.io just no practical example.
So I'm trying to do it with this
#Bean
public DefaultClassMapper typeMapper() {
DefaultClassMapper typeMapper = new DefaultClassMapper();
Map<String, Class> idClassMapping = new HashMap<String, Class>();
idClassMapping.put("range", Loan.class);
typeMapper.setIdClassMapping(idClassMapping);
//typeMapper.setDefaultType(Loan.class);
return typeMapper;
}
#Bean
public MessageConverter messageConverter(DefaultClassMapper defaultClassMapper){
JsonMessageConverter jsonMessageConverter = new JsonMessageConverter();
jsonMessageConverter.setClassMapper(defaultClassMapper);
return jsonMessageConverter;
}
"range" actually fake value from example. Also this really doesn't work type problemn on .setIdClassMapping() . Also I can't use default mapper because serve send header without type hinting field. And I have no control on this remote server. Data format always JSON.
Caused by: org.springframework.amqp.support.converter.MessageConversionException: failed to convert Message content. Could not resolve __TypeId__ in header
Any suggestions working example for marshalling/demarshalling Java objects. I have completely different class for send back value from my code. I'm using java 8.
Just write your own ClassMapper - don't use the default one if your decision criteria to choose the class type is not compatible with its internals.
Or, you can subclass the DefaultClassMapper and override getClassIdFieldName() to tell it which message property to use.
Suppose I have two sets of controllers in Spring:
/jsonapi1/*
/jsonapi2/*
both of which return objects that are to be interpretted as JSON text.
I'd like some kind of filter to wrap the responses from one set of these controllers so that:
the original response is contained within another object.
For example, if /jsonapi1/count returns:
{"num_humans":123, "num_androids":456}
then the response should be wrapped and returned as follows:
{ "status":0,
"content":{"num_humans":123, "num_androids":456}
}
if an exception happens in the controller, then filter should catch the exception and report it as follows
{ "status":5,
"content":"Something terrible happened"
}
The responses from the other controllers are returned unchanged.
We're currently customizing a MappingJackson2HttpMessageConverter passed to WebMvcConfigurerAdapter.configureMessageConverters in order to perform the above tasks. Works great except that it doesn't seem possible for this approach to be selective about the URLs (or controller classes) it applies to.
Is it possible to apply these kinds of wrappers to individual controller classes or URLs?
Update: Servlet filters look like a solution. Is it possible chose which filter gets applied to which controller methods, or which URLs?
I was struggling on this for multiple days. The solution by #Misha didn't work for me. I was able to finally get this working using ControllerAdvice and ResponseBodyAdvice.
ResponseBodyAdvice allows to inject custom transformation logic on the response returned by a controller but before it is converted to HttpResponse and committed.
This is how my controller method looks:
#RequestMapping("/global/hallOfFame")
public List<HallOfFame> getAllHallOfFame() {
return hallOfFameService.getAllHallOfFame();
}
Now i wanted to add some standard fields around the response like devmessage and usermessage. That logic goes into the ResponseAdvice:
#ControllerAdvice
public class TLResponseAdvice implements ResponseBodyAdvice<Object> {
#Override
public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
return true;
}
#Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request,
ServerHttpResponse response) {
// TODO Auto-generated method stub
final RestResponse<Object> output = new RestResponse<>();
output.setData(body);
output.setDevMessage("ResponseAdviceDevMessage");
output.setHttpcode(200);
output.setStatus("Success");
output.setUserMessage("ResponseAdviceUserMessage");
return output;
}
}
The entity classes look like this:
#Setter // All lombok annotations
#Getter
#ToString
public class RestResponse<T> {
private String status;
private int httpcode;
private String devMessage;
private String userMessage;
private T data;
}
#Entity
#Data // Lombok
public class HallOfFame {
#Id
private String id;
private String name;
}
To handle exceptions, simply create another ControllerAdvice with ExceptionHandler. Use the example in this link.
Advantages of this solution:
It keeps your controllers clean. You can support any return type from your controller methods.
Your controller return type class does not need to extend some base class as required by the AOP approach.
You do not need to hack your way through Spring filters by using HttpServletResponseWrappers. They come up with a performance penalty.
EDIT - 17th September 2019
To handle exceptions use #ExceptionHandler. Refer code below.
#ExceptionHandler(Exception.class)
#ResponseBody
public MyResponseEntity<Object> handleControllerException(HttpServletRequest request, Throwable ex) {
// default value
int httpCode = HttpStatus.INTERNAL_SERVER_ERROR.value();
if(ex instanceof ResourceNotFoundException) {
httpCode = HttpStatus.NOT_FOUND.value();
}
...
}
The way I understand your question, you have exactly three choices.
Option #1
Manually wrap your objects in simple SuccessResponse, ErrorResponse, SomethingSortOfWrongResponse, etc. objects that have the fields you require. At this point, you have per-request flexibility, changing the fields on one of the response wrappers is trivial, and the only true drawback is code repetition if many of the controller's request methods can and should be grouped together.
Option #2
As you mentioned, and filter could be designed to do the dirty work, but be wary that Spring filters will NOT give you access to request or response data. Here's an example of what it might look like:
#Component
public class ResponseWrappingFilter extends GenericFilterBean {
#Override
public void doFilter(
ServletRequest request,
ServletResponse response,
FilterChain chain) {
// Perform the rest of the chain, populating the response.
chain.doFilter(request, response);
// No way to read the body from the response here. getBody() doesn't exist.
response.setBody(new ResponseWrapper(response.getStatus(), response.getBody());
}
}
If you find a way to set the body in that filter, then yes, you could easily wrap it up. Otherwise, this option is a dead end.
Option #3
A-ha. So you got this far. Code duplication is not an option, but you insist on wrapping responses from your controller methods. I'd like to introduce the true solution - aspect-oriented programming (AOP), which Spring supports fondly.
If you're not familiar with AOP, the premise is as follows: you define an expression that matches (like a regular expression matches) points in the code. These points are called join points, while the expressions that match them are called pointcuts. You can then opt to execute additional, arbitrary code, called advice, when any pointcut or combination of pointcuts are matched. An object that defines pointcuts and advice is called an aspect.
It's great for expressing yourself more fluently in Java. The only drawback is weaker static type checking. Without further ado, here's your response-wrapping in aspect-oriented programming:
#Aspect
#Component
public class ResponseWrappingAspect {
#Pointcut("within(#org.springframework.stereotype.Controller *)")
public void anyControllerPointcut() {}
#Pointcut("execution(* *(..))")
public void anyMethodPointcut() {}
#AfterReturning(
value = "anyControllerPointcut() && anyMethodPointcut()",
returning = "response")
public Object wrapResponse(Object response) {
// Do whatever logic needs to be done to wrap it correctly.
return new ResponseWrapper(response);
}
#AfterThrowing(
value = "anyControllerPointcut() && anyMethodPointcut()",
throwing = "cause")
public Object wrapException(Exception cause) {
// Do whatever logic needs to be done to wrap it correctly.
return new ErrorResponseWrapper(cause);
}
}
The final result will be the non-repeating response wrapping that you seek. If you only want some or one controller receive this effect, then update the pointcut to match methods only within instances of that controller (rather than any class holding the #Controller annotation).
You'll need to include some AOP dependencies, add the AOP-enabling annotation in a configuration class, and make sure something component-scans the package this class is in.
Simplest way i manage custom responses from controllers is by utilising the Map variable.
so your code ends up looking like:
public #ResponseBody Map controllerName(...) {
Map mapA = new HashMap();
mapA.put("status", "5");
mapA.put("content", "something went south");
return mapA;
}
beauty of is is that you can configure it any thousand ways.
Currently i use for object transmition, custom exception handling and data reporting, too easy.
Hope this helps
I am also using AOP with #Around. Developed a custom annotation and using that for point cut. I am using a global Response. It has the status, Message and data which is of type List of type
List <? extends parent> dataList
( which can solve your class cast exception). All the entities extends this Parent class. This way I can set all the data into my List.
Also I am using the message key as param with the custom annotation and setting it in action.
Hope this helps.
I have successfully set up a quick test of creating a "REST-like" service that returns an object serialized to JSON, and that was quite easy and quick (based on this article).
But while returning JSON-ified objects was easy as peach, I have yet to see any examples dealing with input parameters that are not primitives. How can I pass in a complex object as an argument? I am using Apache CXF, but examples using other frameworks like Jackson are welcome too :)
Client side would probably be something like building a javascript object, pass it into JSON.stringify(complexObj), and pass that string as one of the parameters.
The service would probably look something like this
#Service("myService")
class RestService {
#GET
#Produces("application/json")
#Path("/fooBar")
public Result fooBar(#QueryParam("foo") double foo, #QueryParam("bar") double bar,
#QueryParam("object") MyComplex object) throws WebServiceException {
...
}
}
Sending serialized objects as parameters would probably quickly touch the 2KB URL-limit imposed by Internet Explorer. Would you recommend using POST in these cases, and would I need to change much in the function definitions?
After digging a bit I quickly found out there are basically two options:
Option 1
You pass a "wrapper object" containing all the other parameters to the service. You might need to annotate this wrapper class with JAXB annotations like #XmlRootElement in order for this to work with the Jettison based provider, but if you use Jackson in stead there is no need. Just set the content type to the right type and the right message body reader will be invoked.
This will only work for POST type services of course (AFAIK).
Example
This is just an example of turning the service mentioned in the original question into one using a wrapper object.
#Service("myService")
class RestService {
#POST
#Produces("application/json")
#Path("/fooBar")
public Result fooBar(
/**
* Using "" will inject all form params directly into a ParamsWrapper
* #see http://cxf.apache.org/docs/jax-rs-basics.html
*/
#FormParam("") FooBarParamsWrapper wrapper
) throws WebServiceException {
doSomething(wrapper.foo);
}
}
class ParamsWrapper {
double foo, bar;
MyComplexObject object;
}
Option 2
You can provide some special string format that you pack your objects into and then implement either a constructor taking a string, a static valueOf(String s) or a static fromString(String s) in the class that will take this string and create an object from it. Or quite similar, create a ParameterHandler that does exactly the same.
AFAIK, only the second version will allow you to call your services from a browser using JSONP (since JSONP is a trick restricted to GET). I chose this route to be able to pass arrays of complex objects in the URI.
As an example of how this works, take the following domain class and service
Example
#GET
#Path("myService")
public void myService(#QueryParam("a") MyClass [] myVals) {
//do something
}
class MyClass {
public int foo;
public int bar;
/** Deserializes an Object of class MyClass from its JSON representation */
public static MyClass fromString(String jsonRepresentation) {
ObjectMapper mapper = new ObjectMapper(); //Jackson's JSON marshaller
MyClass o= null;
try {
o = mapper.readValue(jsonRepresentation, MyClass.class );
} catch (IOException e) {
throw new WebApplicationException()
}
return o;
}
}
A URI http://my-server.com/myService?a={"foo":1, "bar":2}&a={"foo":100, "bar":200} would in this case be deserialized into an array composed of two MyClass objects.
2019 comment:
Seeing that this answer still gets some hits in 2019, I feel I should comment. In hindsight, I would not recomment option 2, as going through these steps just to be able to be able to do GET calls adds complexity that's probably not worth it. If your service takes such complex input, you will probably not be able to utilize client side caching anyway, due to the number of permutations of your input. I'd just go for configuring proper Cross-Origin-Sharing (CORS) headers on the server and POST the input. Then focus on caching whatever you can on the server.
The accepted answer is missing #BeanParam. See
https://docs.jboss.org/resteasy/docs/3.0-rc-1/javadocs/javax/ws/rs/BeanParam.html
for further details. It allows you to define query params inside a wrapper object.
E.g.
public class TestPOJO {
#QueryParam("someQueryParam")
private boolean someQueryParam;
public boolean isSomeQueryParam() {
return someQueryParam;
}
public boolean setSomeQueryParam(boolean value) {
this.someQueryParam = value;
}
}
... // inside the Resource class
#GET
#Path("test")
public Response getTest(#BeanParam TestPOJO testPOJO) {
...
}
the best and simplest solution is to send your object as a json string and in server side implement a method which will decode that json and map to the specified object as per your need.. and yes it`s better to use POST.