Spring Boot@Autowired单元测试返回NullPointerException

Question

我有一个用@service注释的类(HttpHandler(。我正在为这个服务类编写单元测试用例。我在测试类中使用了@Autowired注释来获取服务的对象。然而，当我运行单元测试时，它返回NullPOinterException。有人能帮我吗？

以下是服务类别的代码：

@Service
public class HttpHandler {
private static final Logger logger = LoggerFactory.getLogger(HttpHandler.class);
/**
* Build the request and Perform Http Get request with headers
* @param url
* @param httpHeaders
* @param responseClass
* @param <T>
* @param <R>
* @return
*/
public <T,R> ResponseEntity<T> sendPost(String url, HttpHeaders httpHeaders, R requestBody, Class<T> responseClass) {
//create an instance of rest template
RestTemplate restTemplate = new RestTemplate();
HttpEntity<R> entity = new HttpEntity<R>(requestBody, httpHeaders);
logger.info("POST request to " + url + " with body: " + JsonUtil.jsonizeExcludeNulls(requestBody));
//make an HTTP POST request with headers
ResponseEntity<T> response = restTemplate.exchange(url, HttpMethod.POST, entity, responseClass);
logger.info("POST" + url + ": " + JsonUtil.jsonize(response));
return response;
}
}

我正在为POST调用编写单元测试用例。以下是POST调用的单元测试公共类HttpHandlerTest｛

@Autowired
HttpHandler httpHandler;
@Test
public void testSuccessPostUser() throws Exception{
String baseUrl = "http://localhost:8080/users";
List<String> messages = new ArrayList<>();
messages.add("Hi");
User user = new User();
user.setId(1);
user.setName("John");
user.setAge(22);
user.setMessages(messages);
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentType(MediaType.APPLICATION_JSON);
httpHeaders.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
HttpEntity<User> httpEntity = new HttpEntity<>(user, httpHeaders);
ResponseEntity<User> actual = httpHandler.sendPost(baseUrl, httpHeaders, user, User.class);
//verify request succeed
assertEquals(HttpStatus.CREATED, actual.getStatusCode());
assertEquals(201, actual.getStatusCodeValue());
assertTrue(actual.toString().contains("id"));
}

}

它给出以下错误：

java.lang.NullPointerException
at com.xyz.provisioning.xyz.utils.HttpHandlerTest.testSuccessPostUser(HttpHandlerTest.java:41)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:686)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)

Answer 1

对于Junit 5(如注释中所述(，您只需要在测试类的顶部添加@SpringBootTest。

@SpringBootTest
class HttpHandlerTest{
// ...
}

您不需要添加@ExtendWith(SpringExtension.class)，因为它是由注释@SpringBootTest自动导入的。

要获得Junit 4的相同结果：

@RunWith(SpringRunner.class)
@SpringBootTest
class HttpHandlerTest{
// ...
}

Answer 2

如果使用JUnit5，则在类上方添加@ExtendWith(SpringExtension.class)；如果使用JU尼特4，则添加@RunWith(SpringRunner.class)。