Spark java dataframe字符串无法转换为struct

import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.functions;

public class DataFrameExample {
    public static void main(String[] args) {
        SparkSession spark = SparkSession.builder()
                .appName("DataFrameExample")
                .master("local")
                .getOrCreate();

        // 创建DataFrame
        Dataset<Row> df = spark.read()
                .format("csv")
                .option("header", true)
                .load("data.csv");

        // 将字符串列转换为结构体类型
        df = df.withColumn("structColumn", functions.struct(df.col("stringColumn")));

        // 显示DataFrame
        df.show();
    }
}