Spring Junit 测试因 NullPointerException 而失败

Question

我正在为我的 REST API 端点编写 JUnit，我为此创建了一个简单的 hello world 控制器类和 JUnit，但是在执行 JUnit 测试用例时我遇到了异常。如果有人可以帮助我解决这个问题，那将非常有帮助。我正在使用带有 Spring 4.3 版本的 JDK 6

注意：我没有使用 spring-context XML - 我使用的是 Java 注释

HelloController.java

@RestController
@RequestMapping("/hello")
public class HelloController {

    @GetMapping
    public String helloWorld() {

        return "hello World";

    }
}

HelloControllerTest.java

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {HelloController.class})
public class HelloControllerTest {

    private MockMvc mockMvc;

    @InjectMocks
    private HelloController helloController;

    @Before
    public void setUp() throws Exception {
        mockMvc = MockMvcBuilders.standaloneSetup(helloController).build();

    }

    @Test
    public void testHelloWorld() throws Exception {

        mockMvc.perform(MockMvcRequestBuilders.get("/hello")).andExpect(MockMvcResultMatchers.status().isOk())
                .andExpect(MockMvcResultMatchers.content().string("hello World"));

    }
}

例外：

java.lang.NullPointerException
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.detectHandlerMethods(AbstractHandlerMethodMapping.java:227)
    at org.springframework.test.web.servlet.setup.StandaloneMockMvcBuilder$StaticRequestMappingHandlerMapping.registerHandlers(StandaloneMockMvcBuilder.java:486)
    at org.springframework.test.web.servlet.setup.StandaloneMockMvcBuilder.registerMvcSingletons(StandaloneMockMvcBuilder.java:352)
    at org.springframework.test.web.servlet.setup.StandaloneMockMvcBuilder.initWebAppContext(StandaloneMockMvcBuilder.java:337)
    at org.springframework.test.web.servlet.setup.AbstractMockMvcBuilder.build(AbstractMockMvcBuilder.java:139)
    at HelloControllerTest.setUp(HelloControllerTest.java:32)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
    at java.lang.reflect.Method.invoke(Method.java:611)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:538)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:760)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:460)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:206)

Answer 1

如果您使用的是standaloneSetup，则无需使用SpringJUnit4ClassRunner 运行它。那个跑步者需要一个 Spring 配置。

您可以自己初始化一个新的HelloController

例如

public class HelloControllerTest {

    private MockMvc mockMvc;

    private HelloController helloController = new HelloController();

    @Before
    public void setUp() throws Exception {
        mockMvc = MockMvcBuilders.standaloneSetup(helloController).build();

    }

    @Test
    public void testHelloWorld() throws Exception {

        mockMvc.perform(MockMvcRequestBuilders.get("/hello")).andExpect(MockMvcResultMatchers.status().isOk())
                .andExpect(MockMvcResultMatchers.content().string("hello World"));
    }

或者您可以让 Spring 通过注入您的 WebApplicationContext 并使用创建 WebApplicationContext 所需的任何配置来构建它

@RunWith(SpringRunner.class)
@ContextConfiguration(classes = MyWebApplicationConfig.class)
public class HelloControllerTest {

    @Autowired
    private WebApplicationContext wac;

    private MockMvc mockMvc;

    private HelloController helloController;

    @Before
    public void setUp() throws Exception {
        mockMvc = MockMvcBuilders.webAppContextSetup(wac).build();

    }

或者最后，如果你碰巧使用的是 Spring Boot，你可以使用他们的 Slice Test 注释之一，

    @RunWith(SpringRunner.class)
    @WebMvcTest
    public class HelloControllerTest {

    @Autowired 
    private MockMvc mockmvc;

   }

Answer 2

我明白了 - 在 setUp() 中 - 没有实例化 HelloController，在添加下面的行之后，我的测试用例通过了。

helloController = new HelloController();