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kotlin - 反序列化时自定义类上的杰克逊读取值上的 InvalidDefinitionException

问题描述

我正在将InvalidDefinitionExceptionjson 解析为我自己的自定义类。线程“主”com.fasterxml.jackson.databind.exc.InvalidDefinitionException 中的异常：类型的类型定义无效id.or.jisedu.repo.Book：构造函数的参数 #0 [id.or.jisedu.repo.Book 的构造函数，注释：[null]] 没有属性名称注释；当多参数构造函数在 [Source: (String)"..." 处注释为 Creator 时必须具有名称

这是导致问题的行：

val wrapper: BookWrapper = mapper.reader().forType(BookWrapper::class.java).readValue("""
{
  "book": {
    "publisher": "Pearson",
    "image": "https:\/\/images.isbndb.com\/covers\/34\/13\/9780134093413.jpg",
    "title_long": "Campbell Biology (11th Edition)",
    "edition": "11",
    "date_published": "2016-10-29",
    "authors": [
      "Lisa A. Urry",
      "Michael L. Cain",
      "Steven A. Wasserman",
      "Peter V. Minorsky",
      "Jane B. Reece"
    ],
    "title": "Campbell Biology (11th Edition)",
    "isbn13": "9780134093413",
    "binding": "Hardcover",
    "publish_date": "2016-10-29",
    "isbn": "0134093410"
  }
}""")

这是我的书包类：

data class BookWrapper(@JsonProperty("book") val book: Book)

@JsonInclude(JsonInclude.Include.NON_NULL)
data class Book(
  val title: String,
  @JsonProperty("title_long")
  val titleLong: String? = null,
  val isbn: String? = null,
  val isbn13: String? = null,
  val dewey_decimal: String? = null,
  val format: String? = null,
  val publisher: String? = null,
  val publish: String? = null,
  val language: String? = null,
  @JsonProperty("date_published")
  val datePublished: String? = null,
  @JsonProperty("publish_date")
  val publishDate: String? = null,
  val edition: String? = null,
  val pages: String? = null,
  val binding: String? = null,
  val dimensions: String? = null,
  val overview: String? = null,
  val excerpt: String? = null,
  val synopsys: String? = null,
  val image: String? = null,
  val authors: List<String>,
  val subjects: List<String>? = null,
  var id: Long? = null,
  var amount: Int = 1
)

编辑：

我忘记注册 KotlinModule。不要忘记这样做。

标签： kotlinjackson

解决方案

是的，注册 KotlinModule 会有所帮助。注册 Kotlin 模块：

  1. 将依赖项添加到 build.gradle：

    implementation("com.fasterxml.jackson.module:jackson-module-kotlin:2.9.8")

  2. 创建对象映射器：

    import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper val mapper = jacksonObjectMapper()

更多信息，请访问https://www.baeldung.com/kotlin/jackson-kotlin

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