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，它会在调用模拟 restTemplate 的行上不断抛出 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？我之前嘲笑过一个 RestTemplate ，只是没有 getBody() 方法，这导致人们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();

最初您设置的是ResponseEntity唯一的并且RestTemplate仍然保留默认值..因此在exchange被调用时返回 null 。