MockMvc 使用 application/json 返回 HttpMessageNotWritableException

Question

我有一个 spring 2.3.4.RELEASE 的休息端点当我使用 MockMvc 运行控制器测试时，我收到了

wsmsDefaultHandlerExceptionResolver ：已解决[org.springframework.http.converter.HttpMessageNotWritableException：没有带有预设内容类型“application/json”的[class com.example.myexample.model.User]转换器]

@SpringBootTest(classes = UserController.class)
@ExtendWith(SpringExtension.class)
@AutoConfigureMockMvc
public class UserControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private UserRepository userRepository;

    private static final String GET_USERBYID_URL = "/users/{userId}";
    

    @Test
    public void shouldGetUserWhenValid() throws Exception {
        Address address = new Address();
        address.setStreet("1 Abc St.");
        address.setCity("Paris");

        User userMock = new User();
        userMock.setFirstname("Lary");
        userMock.setLastname("Pat");
        userMock.setAddress(address);

        when(userRepository.findById(1)).thenReturn(Optional.of(userMock));

        mockMvc.perform(get(GET_USERBYID_URL, "1").accept(MediaType.APPLICATION_JSON))
               .andDo(print())
               .andExpect(status().isOk());
    }
}


@RestController
@RequestMapping(path = "/users")
@Slf4j
public class UserController {

    @Autowired
    private UserRepository userRepository;

    @GetMapping(value = "/{userId}", produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<User> getUser(@PathVariable("userId") Integer userId) {
        log.info("Getting user with id={}", userId);
        final Optional<User> userOptional = userRepository.findById(userId)

        return userOptional.map(value -> ResponseEntity.ok()
                                               .contentType(MediaType.APPLICATION_JSON)
                                               .body(value))
                   .orElseGet(() -> ResponseEntity.noContent()
                                                  .build()).ok()
                           .body(userOptional.get());

    }
}


@Data
public class User {
    private String firstname;
    private String lastname;
    private Address address;
}

@Data
public class Address {
    private String street;
    private String city;
}

@Repository
public interface UserRepository extends CrudRepository<User, Integer> {
}

我读过其他建议添加杰克逊依赖的文章，但这对我不起作用。

<dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.11.3</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.11.3</version>
        </dependency>

这是我的 pom.xml

<?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 http://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>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

<groupId>org.example</groupId>
<artifactId>myexample</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
    <java.version>1.8</java.version>
    <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
    <lombok.version>1.18.12</lombok.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-validation</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <version>RELEASE</version>
        <scope>compile</scope>
    </dependency>
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>${lombok.version}</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.11.3</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.11.3</version>
    </dependency>



    <!-- test dependencies -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <source>${java.version}</source>
                <target>${java.version}</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

如果我运行应用程序并通过邮递员测试它，端点工作正常。有什么想法为什么我在休息控制器测试中收到此错误消息吗？

Answer 1

问题在于你的@SpringBootTest，当你添加时classes = UserController.class，它告诉spring创建一个上下文UserController.class。所以它只使用 UserController 创建 spring 上下文。因此，仅创建您的控制器 bean，而不会创建 Http 消息转换所需的其他 bean。所以一种解决方案是classes = UserController.class从@SpringBootTest.

@SpringBootTest
@ExtendWith(SpringExtension.class)
@AutoConfigureMockMvc

现在运行测试应该没有问题了。
但这带来了另一个问题，现在这将加载完整的 spring 上下文，而这仅是控制器层测试所不需要的。它还会增加单元测试的时间。
为了解决这个问题，spring还有一个注解@WebMvcTest。如果您使用 @WebMvcTest 注释您的测试，Spring Boot 只会实例化 Web 层而不是整个上下文。您还可以选择仅实例化一个控制器。例如，

@ExtendWith(SpringExtension.class)
@WebMvcTest(UserController.class)
public class UserControllerTest {

}

这应该可以解决你的问题。