Spring Boot自动连线服务和存储库抛出nullpointerexception

Question

我正在测试一个简单的初学者spring boot应用程序，但是它会不断为我的服务类和存储库类抛出NullPointerException。
这是我的控制器类：

@EnableAutoConfiguration
@RestController
public class MyController {

    @Autowired
    private MyService service;


    @GetMapping("/welcome")
    public String home throws IOException {
        return service.getEntities();
    }

}

这是Service类：

@EnableAutoConfiguration
@Service
public class MyService{

@Autowired(required=true)
private MyRepository repository;

public MyService() {
};

public List<Entity> getEntities() throws IOException {
        return repository.findAll();
    }

这是存储库：

@Repository
public interface MyRepository extends JpaRepository<Entity, Long>{

    List<Entity> findAll();

}

因此，如果我运行该应用程序，一切正常。问题是当我运行此测试时：

@RunWith(SpringRunner.class)
@ContextConfiguration(classes = { MyService.class, MyController.class, Entity.class })
@ComponentScan("test.firstproject")
@EntityScan(basePackages = {"test.firstproject.entities"})
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureTestDatabase(replace = Replace.NONE)
@EnableJpaRepositories("test.firstproject.repository")
@EnableAutoConfiguration
public class TestController {

    private MockMvc mvc = MockMvcBuilders.standaloneSetup(new MyController).build();

    public static final MediaType APPLICATION_JSON_UTF8 = new MediaType(MediaType.APPLICATION_JSON.getType(), MediaType.APPLICATION_JSON.getSubtype(), Charset.forName("utf8"));

    @Autowired
    private ObjectMapper objectMapper;


    @Test
    public void allEntities() {
        this.objectMapper = new ObjectMapper();
        try {
            ResultActions resultActions = this.mvc
                    .perform(MockMvcRequestBuilders.get("/welcome").accept(MediaType.APPLICATION_JSON));
             this.mvc.perform(get("/welcome")).andExpect(status().isOk());
             MvcResult result = resultActions.andReturn();
             List<Object> list = objectMapper.readValue(result.getResponse().getContentAsString(), new TypeReference<List<Entity>>(){});
             for (Object c : list) {
                 assertTrue(c.getClass().equals(Entity.class));
             }

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

首先，它在调用service.getEntities()时引发NullPointerException。然后，我尝试通过= new MyService()初始化服务，但是这次return repository.findAll();引发了错误。怎么了？

编辑-Stacktrace

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1013)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
    at org.springframework.test.web.servlet.TestDispatcherServlet.service(TestDispatcherServlet.java:71)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.springframework.mock.web.MockFilterChain$ServletFilterProxy.doFilter(MockFilterChain.java:166)
    at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:133)
    at org.springframework.test.web.servlet.MockMvc.perform(MockMvc.java:182)
    at com.example.demo.TestController.getAllEntities(TestController.java:58)
    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.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.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)
    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:251)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    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:190)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
Caused by: java.lang.NullPointerException
    at com.springmiddleware.controllers.MyController.allEntities(MyController.java:32)
    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.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
    ... 40 more

Answer 1

您在以下行中使用new创建了MyController：

private MockMvc mvc = MockMvcBuilders.standaloneSetup(new MyController()).build();

Spring可能没有向其注入Service。尝试自动接线：

@Autowired
private MyController myController;

并将MockMvc实例化到@Before方法：

private MockMvc mvc;

@Before
public void initialize() {
    mvc = MockMvcBuilders.standaloneSetup(myController).build();
}