Question

我想在Scala中用jackson反序列化json

import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.scala.DefaultScalaModule
import com.fasterxml.jackson.module.scala.experimental.ScalaObjectMapper
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize; 
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonCreator; 



case class Metadata(@JsonProperty("hive_type_string") hive_type_string: String)

case class Field(@JsonProperty("name") name: String, @JsonProperty("type") typeField: String, @JsonProperty("nullable") nullable: Boolean, @JsonProperty("metadata") metadata: Metadata) 

case class StructTable(@JsonProperty("type") typeField: String, @JsonProperty("fields") fields: Seq[Field])


val mapper = new ObjectMapper() with ScalaObjectMapper
mapper.registerModule(DefaultScalaModule)
val struct = mapper.readValue[StructTable](json_struct)

json_struct :

{ "类型":"结构", “领域”：[ { "name":"code_role", "类型":"字符串", “可为空”：真， “元数据”：{ "HIVE_TYPE_STRING":"字符串" } }, { "name":"libelle_role", "类型":"字符串", “可为空”：真， “元数据”：{ "HIVE_TYPE_STRING":"字符串" } } ] }

这是错误：com.fasterxml.jackson.databind.exc.InvalidDefinitionException：无法构造StructTable的实例：像这样的非静态内部类只能通过使用默认的无参数实例化构造函数

有人可以帮我吗？

谢谢。

Answer 1

如果您可以选择另一个库，例如 jsoniter-scala，请添加到您的依赖项中：

libraryDependencies ++= Seq(
  // Use the %%% operator instead of %% for Scala.js  
  "com.github.plokhotnyuk.jsoniter-scala" %% "jsoniter-scala-core"   % "2.6.2",
  // Use the "provided" scope instead when the "compile-internal" scope is not supported in your build tool
  "com.github.plokhotnyuk.jsoniter-scala" %% "jsoniter-scala-macros" % "2.6.2" % "compile-internal"
)

以下是解析输入并打印解析数据的代码片段：

import com.github.plokhotnyuk.jsoniter_scala.macros._
import com.github.plokhotnyuk.jsoniter_scala.core._

case class Metadata(@named("HIVE_TYPE_STRING") hive_type_string: String)

case class Field(name: String, @named("type") typeField: String, nullable: Boolean, metadata: Metadata)

case class StructTable(@named("type") typeField: String, fields: Seq[Field])

implicit val codec: JsonValueCodec[StructTable] = JsonCodecMaker.make

val json_struct = """{ "type":"struct", "fields":[ { "name":"code_role", "type":"string", "nullable":true, "metadata":{ "HIVE_TYPE_STRING":"string" } }, { "name":"libelle_role", "type":"string", "nullable":true, "metadata":{ "HIVE_TYPE_STRING":"string" } } ] }""";
val struct = readFromString(json_struct)

println(struct)

预期输出为：

StructTable(struct,List(Field(code_role,string,true,Metadata(string)), Field(libelle_role,string,true,Metadata(string))))

您也可以使用 Scastie here 在线运行它。

Scala 杰克逊反序列化

1 个答案: