如何在使用spark将json文档写入Mongo DB时将自定义值设置为_id字段

import org.apache.spark.sql.SparkSession
import com.mongodb.spark.MongoSpark
import org.bson.Document

val spark = SparkSession.builder()
  .appName("Write JSON to MongoDB")
  .config("spark.mongodb.output.uri", "mongodb://localhost/test.collection")
  .getOrCreate()

val jsonData = Seq(
  """{"name": "John", "age": 30, "custom_id": "custom1"}""",
  """{"name": "Jane", "age": 25, "custom_id": "custom2"}"""
)
val df = spark.read.json(spark.sparkContext.parallelize(jsonData))

val customIdField = "_id"
val dfWithCustomId = df.withColumn(customIdField, df("custom_id"))
MongoSpark.save(dfWithCustomId)