Mockito：抛出指定的已检查异常时，“已检查异常对此方法无效”

Question

There are several questions around this on StackOverflow, but I believe this case to be different. I'm using Java 11 and Mockito 2.11.0.

Here's a minimal JUnit 4 test case demonstrating my problem:

@Test
public void shouldAllowMocking() throws Exception {
  ObjectMapper objectMapper = mock(ObjectMapper.class);
  when(objectMapper.readValue(anyString(), any(Class.class))).thenThrow(new IOException("the-message"));
}

I'm mocking the behaviour of Jackson's ObjectMapper's readValue(String content, Class<T> valueType) method - documentation here - and the documentation shows that that method can throw an IOException . So why does Mockito report that it is invalid for me to mock throwing such an exception?

Interestingly, if I change the behaviour to throw a JsonParseException , which can also be thrown by that method, then Mockito doesn't complain.

Answer 1

Since version 2.10 Jackson removed the IOException, this is the portion of the code:

@SuppressWarnings("unchecked")
public <T> T readValue(String content, JavaType valueType)
    throws JsonProcessingException, JsonMappingException
{
    _assertNotNull("content", content);
    try { // since 2.10 remove "impossible" IOException as per [databind#1675]
        return (T) _readMapAndClose(_jsonFactory.createParser(content), valueType);
    } catch (JsonProcessingException e) {
        throw e;
    } catch (IOException e) { // shouldn't really happen but being declared need to
        throw JsonMappingException.fromUnexpectedIOE(e);
    }
} 

The link you included in the question points to the jakson-databind 2.7 so I assume you are checking the wrong doc.

Answer 2

This turns out to be because I'd unintentionally updated my jackson version as well, and the newer versions (2.11.x) don't throw IOException any more.