java - StringType 问题 : Exception in thread "main" scala. MatchError : org. apache.spark.sql.types.StringType@

Question

@Override
public Option<DataType> getCatalystType(int sqlType, String typeName, int size, MetadataBuilder md) {
    switch (sqlType) {
    case java.sql.Types.JAVA_OBJECT:
        switch (typeName) {
        case "map(varchar(2147483647),varchar(2147483647))":
            return Option.apply(DataTypes.createMapType(new StringType(), new StringType()));               
        }
        break;
    }
    return super.getCatalystType(sqlType, typeName, size, md);      
}

代码用于在返回JAVA_OBJECT时支持复杂数据类型。同样的代码，我用 Scala 编写，运行良好。但是当在 Java 中使用上面的代码时，它给出了:

线程“主”scala.MatchError 中的异常:org.apache.spark.sql.types.StringType@582b14e2(类 org.apache.spark.sql.types.StringType)。

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供引用的 Scala 代码:

override def getCatalystType(sqlType: Int, typeName: String, size: Int, md: MetadataBuilder): Option[DataType] = sqlType match {
    case java.sql.Types.JAVA_OBJECT =>
      typeName match {
        case "map(varchar(2147483647),varchar(2147483647))" => Option(DataTypes.createMapType(StringType, StringType))
        case "BIT" => Option(BooleanType)
        case _ => None
      }
    case _ => None
  }

Answer 1

改用单例 DataTypes.StringType( as recommended ):

...
...(DataTypes.createMapType(DataTypes.StringType, DataTypes.StringType))          

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The data type representing String values. Please use the singletonDataTypes.StringType.