[英]Null pointer exception when using Mockito to mock interface
I'm using Mockito to test the following method:我正在使用 Mockito 来测试以下方法:
protected void produceProducedFieldValue(Target target) throws ValueProducerCreationException {
String mappedValue = (String) valueProducerFactory.createValueProducer("IdProducer", Collections.emptyList()).get();
target.setProducedField(mappedValue);
}
Here is my test:这是我的测试:
@Test
public void TestProducingProducedFieldValue() throws ValueProducerCreationException {
Target mockedTarget = Mockito.mock(Target.class);
ValueProducerFactory valueProducerFactory = Mockito.mock(ValueProducerFactory.class);
List<Object> creationParameters = new ArrayList<>();
String mappedValue= "SomeString";
Mockito.when(valueProducerFactory.createValueProducer("IdProducer", Collections.emptyList()).get()).thenReturn(mappedValue);
SourceToTargetMapper sttm = new SourceToTargetMapper(targetModelObjectFactory,mappingOperatorFactory,mapperFactory,valueProducerFactory);
sttm.produceProducedFieldValue(mockedTarget);
Mockito.verify(mockedTarget, Mockito.times(1)).setProducedField(Mockito.any());
}
But I keep getting NullPointerExeption
for this line:但我不断收到此行的NullPointerExeption
:
Mockito.when(valueProducerFactory.createValueProducer("IdProducer", Collections.emptyList()).get()).thenReturn(mappedValue);
ValueProducerFactory
is an Interface ValueProducerFactory
是一个接口
and the createValueProducer
method signature is as follows:而createValueProducer
方法签名如下:
public interface ValueProducerFactory {
<T> Supplier<T> createValueProducer(String producerName, List<Object> creationParameters) throws ValueProducerCreationException;
}
I have a class named CachingValueProducerFactory that implements the interface我有一个名为 CachingValueProducerFactory 的类,它实现了接口
@Override
public <T> Supplier<T> createValueProducer(String producerName, List<Object> creationParameters) throws ValueProducerCreationException {
Map<List<Object>, Supplier<?>> parametersToOperatorsMap = producersCache.computeIfAbsent(producerName, s -> new HashMap<>());
List<Object> key = Optional.ofNullable(creationParameters).orElse(Collections.emptyList());
if (!parametersToOperatorsMap.containsKey(key)) {
parametersToOperatorsMap.put(key, nestedProducersFactory.createValueProducer(producerName, creationParameters));
}
return (Supplier<T>) parametersToOperatorsMap.get(key);
}
It seems like using Collections.emptyList()
in the test is the problem, but I don't see any other solution for this.在测试中使用Collections.emptyList()
似乎是问题所在,但我没有看到任何其他解决方案。
You are trying to mock two methods at once.您正在尝试同时模拟两种方法。 In this line:在这一行:
Mockito.when(valueProducerFactory.createValueProducer("IdProducer", Collections.emptyList()).get()).thenReturn(mappedValue);
you are calling get()
on the result of the createValueProducer()
call, which is null
because you haven't mocked it yet.您正在对createValueProducer()
调用的结果调用get()
,该结果为null
因为您尚未对其进行createValueProducer()
。
There are two solutions:有两种解决方案:
Use deep stubbing :使用深存根:
ValueProducerFactory valueProducerFactory = Mockito.mock(ValueProducerFactory.class, Mockito.RETURNS_DEEP_STUBS);
Mockito.when(valueProducerFactory.createValueProducer("IdProducer", Collections.emptyList()).get()).thenReturn(mappedValue);
Mock the Supplier first (pay attention to the removed get()
):首先模拟供应商(注意移除的get()
):
Supplier<Object> supplier = () -> mappedValue;
ValueProducerFactory valueProducerFactory = Mockito.mock(ValueProducerFactory.class);
Mockito.when(valueProducerFactory.createValueProducer("IdProducer", Collections.emptyList())).thenReturn(supplier);
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