我很困惑为什么以下代码从标题中引发异常：

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

        JavaSparkContext javaSparkContext = new JavaSparkContext(spark.sparkContext());
        JavaRDD<String> javaRdd = javaSparkContext.parallelize(Arrays.asList("a","b","c"));
        JavaRDD<Foo> simpleRdd = javaRdd.map(Foo::new);

        Dataset fooDs = spark.createDataset(simpleRdd.rdd(),Encoders.bean(Foo.class)); // works perfectly
        UDF1<String,Bar> newBar = Bar::new;
        UserDefinedFunction newBarUdf = udf(newBar,Encoders.bean(Bar.class).schema());
        Dataset fooBarDs = fooDs.withColumn("test",newBarUdf.apply(col("name"))); // doesn't work

        fooBarDs.show(false);
    }

    public static class Bar implements Serializable {
        private String alias;

        public Bar(String alias) {
            this.alias = alias;
        }

        public Bar() {
        }

        public String getalias() {
            return alias;
        }

        public void setalias(String alias) {
            this.alias = alias;
        }
    }

    public static class Foo implements Serializable {
        private String name;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public Foo(String name) {
            this.name = name;
        }

        public Foo() {
        }
    }
}

有人知道为什么不支持此操作吗，因为感觉应该如此。我究竟做错了什么？有解决方法吗？

注意：实际示例中有几列具有原始字段，我需要能够将Java类转换为嵌套结构的列。