java - RestTemplate 模拟抛出 NullPointerException

Question

我有一个休息模板，它在服务类中的方法中进行调用，如下所示:

public CustomerResponse someMethod() {
CustomerResponse response = restTemplate.exchange(url, HttpMethod.GET, null,  CustomerRes.class).getBody();
return response;
}

当尝试在我的测试类中模拟restTemplate时，它不断在调用模拟restTemplate的行上抛出NullPointerException:

public void checkResponseIsNotNull() {
CustomerResponse customerResponseMock = mock(CustomerResponse.class);
when(restTemplate.exchange(url, HttpMethod.GET, null, CustomerResponse.class).getBody()).thenReturn(customerResponseMock);
CustomerResponse cr = service.someMethod();
Assert.assertNotNull(cr);
}

为什么会抛出 NullPointer？我之前模拟过 RestTemplate，只是没有 getBody() 方法，这导致我相信它是导致空指针的原因。

Answer 1

您应该再添加一层模拟:

CustomerResponse customerResponseMock = mock(CustomerResponse.class);
ResponseEntity reMock = mock(ResponseEntity.class);

when(reMock.getBody()).thenReturn(customerResponseMock);
when(restTemplate.exchange(url, HttpMethod.GET, null, CustomerResponse.class)).thenReturn(reMock);

CustomerResponse cr = service.someMethod();

最初，您仅设置了 ResponseEntity，而 RestTemplate 仍保留默认值。因此，当 exchange 已设置时返回 null已调用。