用Spark和Java连接MongoDB的问题

<dependency>
    <groupId>org.apache.spark</groupId>
    <artifactId>spark-core_2.11</artifactId>
    <version>2.4.8</version>
</dependency>

<dependency>
    <groupId>org.mongodb.spark</groupId>
    <artifactId>mongo-spark-connector_2.11</artifactId>
    <version>2.4.2</version>
</dependency>

SparkSession spark = SparkSession.builder()
    .appName("MongoDBExample")
    .config("spark.mongodb.input.uri", "mongodb://localhost/testDB.collectionName")
    .config("spark.mongodb.output.uri", "mongodb://localhost/testDB.collectionName")
    .getOrCreate();

Dataset<Row> mongoData = spark.read().format("com.mongodb.spark.sql.DefaultSource")
    .option("uri", "mongodb://localhost/testDB.collectionName")
    .load();

Dataset<Row> data = ... // 要写入MongoDB的数据

data.write().format("com.mongodb.spark.sql.DefaultSource")
    .option("uri", "mongodb://localhost/testDB.collectionName")
    .mode("append")
    .save();