Spring5.0.4& Jackson2在启动时抛出例外

Question

我试图做简单的休息服务，但面临两个问题。1. REST控制器的任何方法返回406 http错误；

@GetMapping(value = "/getUser/{id}", headers = "Accept=application/json",
        produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
@ResponseBody
public ResponseEntity<Object> getUser(@PathVariable(value = "id")Long id) {
    if (id == null) return new ResponseEntity<>(HttpStatus.BAD_REQUEST);
    UserInfo userInfo = userService.get(id);


    if (userInfo == null) return new ResponseEntity<>(HttpStatus.NOT_FOUND);
    return new ResponseEntity<>(userInfo, HttpStatus.OK);
}
@GetMapping(value = "/getUsers", headers = "Accept=application/json",produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public List<UserInfo> getUsers()
{
    return userService.getAll();
}

所以谷歌告诉我，这个问题可能是因为缺少Jackson2依赖关系。但是，添加此依赖项会导致此错误，添加较低的版本将导致相同的输出或406。

 <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.4.4</version>
    </dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.4.4</version>
</dependency>


> 06-May-2018 15:36:45.477 WARNING [http-nio-25565-exec-3]
> org.springframework.context.support.AbstractApplicationContext.refresh
> Exception encountered during context initialization - cancelling
> refresh attempt:
> org.springframework.beans.factory.BeanCreationException: Error
> creating bean with name 'requestMappingHandlerAdapter' defined in
> class path resource
> [org/springframework/web/servlet/config/annotation/DelegatingWebMvcConfiguration.class]:
> Bean instantiation via factory method failed; nested exception is
> org.springframework.beans.BeanInstantiationException: Failed to
> instantiate
> [org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter]:
> Factory method 'requestMappingHandlerAdapter' threw exception; nested
> exception is java.lang.NoClassDefFoundError:
> com/fasterxml/jackson/databind/exc/InvalidDefinitionException

我做错了什么？

Answer 1

在Spring 5或更高版本中，BeanInstantiationException类负责将java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/exc/InvalidDefinitionException作为嵌套异常抛出。

从上面的异常可以看出，此异常的根本原因是缺少类InvalidDefinitionException.。此类从2.9.0版本起已在jackson databind API中引入。

因此，要解决这个问题，只需使用版本2.9.0或更高版本添加jackson数据库依赖项

        **<groupId>com.fasterxml.jackson.core</groupId>**

        **<artifactId>jackson-databind</artifactId>**

        **<version>2.9.0</version>**

谢谢!！