json - kotlin 数据类 HttpMessageNotReadableException

Question

我正在用 postman 尝试这段代码，但没有任何效果，为什么？

我寄什么:

{
    "name":"front_msel",
    "gitlabId": "83",
    "fichierVersion":"VERSION"
}

我的 Spring Controller :

@RestController
@RequestMapping("/projects")
class ProjectController(val projectRepository: ProjectRepository) {
    private val log = LoggerFactory.getLogger(ProjectController::class.java)

    @PostMapping()
    fun saveProject(@RequestBody payload: Project): String {
        log.info("project: '{}'", payload.toString())
       return projectRepository.save(payload).gitlabId?:"-1"
    }

}

我得到什么:

{
"timestamp": 1505917417221,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.http.converter.HttpMessageNotReadableException",
"message": "JSON parse error: Can not construct instance of com.......model.Project: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.......model.Project: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)\n at [Source: java.io.PushbackInputStream@66ba61d9; line: 2, column: 2]",
"path": "/projects"

}

我的项目数据类:

data class Project(val name:String?, val gitlabId: String?, val fichierVersion: String?)

我加倍检查参数，这不是一个措辞错误，这东西不起作用是什么？

编辑:

感谢 Todd，通过向我的参数添加 null 值来生成零参数构造函数来解决问题。谢谢 !

data class Project(val name:String? = null, val gitlabId: String? = null, val fichierVersion: String? = null)

Answer 1

我通过做了两个细微的改变来实现这一点。

首先，因为你所有的Project字段可以为空，提供默认值以便编译器生成一个零参数构造函数:

data class Project(val name:String? = null, val gitlabId: String? = null, val fichierVersion: String? = null)

其次，Spring 似乎希望您的字段位于 snakey_case 中。而不是 camelCase ，因此将您的有效负载更改为:

{
  "name":"front_msel",
  "gitlab_id": "83",
  "fichier_version":"VERSION"
}