Spring Boot使用MockMvc测试时的一次小坑

Spring Boot 版本为 1.5.13.RELEASE

一个基本的RESTful API小案例，正常启动Spring Boot无异常，接口访问全部正常通过。

在其他配置全部一致的情况下，使用MockMvc进行测试抛出异常：

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
	at org.springframework.test.web.servlet.TestDispatcherServlet.service(TestDispatcherServlet.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	at org.springframework.mock.web.MockFilterChain$ServletFilterProxy.doFilter(MockFilterChain.java:160)
	at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:127)
	at org.springframework.test.web.servlet.MockMvc.perform(MockMvc.java:151)
	at com.tanwubo.Demo04ApplicationTests.userControllerTest(Demo04ApplicationTests.java:70)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	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.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	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:459)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.lang.NullPointerException
	at com.tanwubo.controller.UserController.findById(UserController.java:30)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
	... 39 more

测试类:

@RunWith(SpringRunner.class)
@SpringBootTest(classes = { Demo04Application.class, MockServletContext.class })
public class Demo04ApplicationTests {
	private MockMvc mvc;
	@Before
	public void setUp() throws Exception {
		mvc = MockMvcBuilders.standaloneSetup(new UserController()).build();
	}
	@Test
	public void userControllerTest() throws Exception {
		// 测试UserController
		RequestBuilder request = null;
		request = get("/users/2");
		mvc.perform(request).andExpect(status().isOk()).andExpect(content().string(equalTo(
				"{\"msg\":\"成功\",\"code\":200,\"user\":{\"id\":2,\"username\":\"admin\",\"password\":\"admin\"}}")));
	}

}

后将MockMvc的创建方式由 mvc = MockMvcBuilders.standaloneSetup(new UserController()).build();

修改为 mvc = MockMvcBuilders.webAppContextSetup(this.context).build();测试成功。具体原因不详，故做此记录。

修改后的代码：

@RunWith(SpringRunner.class)
@SpringBootTest(classes = { Demo04Application.class, MockServletContext.class })
public class Demo04ApplicationTests {
	@Autowired
	private WebApplicationContext context;
	private MockMvc mvc;
	@Before
	public void setUp() throws Exception {
		mvc = MockMvcBuilders.webAppContextSetup(this.context).build();
	}
	@Test
	public void userControllerTest() throws Exception {
		// 测试UserController
		RequestBuilder request = null;
		request = get("/users/2");
		mvc.perform(request).andExpect(status().isOk()).andExpect(content().string(equalTo(
				"{\"msg\":\"成功\",\"code\":200,\"user\":{\"id\":2,\"username\":\"admin\",\"password\":\"admin\"}}")));
	}

}