Spring Boot RestController测试类Mock变量无法实例化问题

云原生阿岚

2026-8-12

Spring Boot RestController单元测试Mock变量实例化失败问题排查

问题描述

为Spring Boot的RestController编写单元测试时，mockMvc和service变量均为null，按预期它们应该通过Spring注解完成实例化。使用Spring Boot 2.7.4 + Java 11，已引入spring-boot-starter-test依赖，排查过JUnit版本混用问题但未解决。

相关代码

Controller代码

@RestController()
@RequestMapping("/endpoint")
public class MyRestController {
    
    @Autowired
    private MyService service;

    @GetMapping(value = "/{id}", produces = "application/json")
    public ResponseEntity<String> findSomethingById(@PathVariable("id") String id, @RequestParam("param1")String param1) throws MyServiceException {
        return ResponseEntity.ok(service.findSomethingById(id,param1));
    }
}

测试类代码

import org.junit.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import org.springframework.test.web.servlet.MockMvc;

import static org.hamcrest.Matchers.hasSize;
import static org.hamcrest.Matchers.isA;
import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

@ExtendWith(SpringExtension.class)
@WebMvcTest(MyRestController.class)
public class MyRestControllerUnitTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private MyService service;


    @Test
    public void testGetSomethingId() throws Exception {
        when(service.findSomethingById("1", "something")).thenReturn("found");
        mockMvc.perform(get("/endpoint/1").param("param1","something"))
                .andDo(print())
                .andExpect(status().isOk());
                // some more Expects
    }
}

主类代码

@SpringBootApplication
public class MyApplication {

    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }

}

pom.xml代码

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>org.myGroup</groupId>
    <artifactId>myArtifact</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <name>MyApplication</name>

    <properties>
        <java.version>11</java.version>
        <spring-cloud.version>2020.0.3</spring-cloud.version>
        <start-class>org.main.MyApplication</start-class>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springdoc</groupId>
            <artifactId>springdoc-openapi-ui</artifactId>
            <version>1.6.12</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.slf4j</groupId>
                    <artifactId>slf4j-api</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>

        <dependency>
            <groupId>javax.validation</groupId>
            <artifactId>validation-api</artifactId>
        </dependency>
        <dependency>
            <groupId>org.hibernate.validator</groupId>
            <artifactId>hibernate-validator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-source-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>org.main.MyApplication</mainClass>
                        </manifest>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <id>attach-sources</id>
                        <goals>
                            <goal>jar</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

测试执行堆栈信息

java.lang.NullPointerException
    at MyRestControllerUnitTest.findSomethingById(Line of when() as service is null and so is mockMvc)
    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:59)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
    at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
    at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
    at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
    at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:80)
    at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:72)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
    at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
    at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
    at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)


Process finished with exit code -1

问题原因及解决方案

从堆栈信息可以看到，测试是通过JUnit 4的BlockJUnit4ClassRunner执行的，但测试类使用了JUnit 5的@ExtendWith(SpringExtension.class)注解，同时pom.xml中同时引入了JUnit 4和JUnit 5的依赖，导致Spring无法正确初始化测试上下文。

解决步骤：

移除JUnit 4依赖：在pom.xml中删除单独的junit依赖：
```
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <scope>test</scope>
</dependency>
```
spring-boot-starter-test已经包含了JUnit 5的相关依赖，不需要单独引入JUnit 4。
替换JUnit 4的@Test注解：测试类中使用的org.junit.Test是JUnit 4的注解，替换为JUnit 5的org.junit.jupiter.api.Test：
```
// 替换import
import org.junit.jupiter.api.Test;
```
简化测试类注解（可选）：Spring Boot 2.2+版本中，@WebMvcTest已经默认包含了@ExtendWith(SpringExtension.class)，可以移除该注解，简化测试类：
```
// 移除@ExtendWith(SpringExtension.class)
@WebMvcTest(MyRestController.class)
public class MyRestControllerUnitTest {
    // ... 代码不变
}
```
清理并重新构建项目：执行mvn clean test重新运行测试，此时Spring应该能正确初始化mockMvc和service实例。

内容的提问来源于stack exchange，提问作者tung

Spring Boot RestController测试类Mock变量无法实例化问题

问题描述 #

相关代码 #

Controller代码 #

测试类代码 #

主类代码 #

pom.xml代码 #

测试执行堆栈信息 #

问题原因及解决方案 #

解决步骤： #