Dataset<Tweet> ds = sc.read().json("path").as(Encoders.bean(Tweet.class)); ds.show(); JavaRDD<Tweet> dstry = ds.toJavaRDD(); System.out.println(dstry.first().getClass()); Caused by: java.util.concurrent.ExecutionException: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 50, Column 16: failed to compile: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 50, Column 16: No applicable constructor/method found for actual parameters "org.apache.spark.unsafe.types.UTF8String"; candidates are: "public void sparkSQL.Tweet.setId(long)" at org.spark_project.guava.util.concurrent.AbstractFuture$Sync.getValue(AbstractFuture.java:306) at org.spark_project.guava.util.concurrent.AbstractFuture$Sync.get(AbstractFuture.java:293) at org.spark_project.guava.util.concurrent.AbstractFuture.get(AbstractFuture.java:116) at org.spark_project.guava.util.concurrent.Uninterruptibles.getUninterruptibly(Uninterruptibles.java:135) at org.spark_project.guava.cache.LocalCache$Segment.getAndRecordStats(LocalCache.java:2410) at org.spark_project.guava.cache.LocalCache$Segment.loadSync(LocalCache.java:2380) at org.spark_project.guava.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2342) at org.spark_project.guava.cache.LocalCache$Segment.get(LocalCache.java:2257) at org.spark_project.guava.cache.LocalCache.get(LocalCache.java:4000) at org.spark_project.guava.cache.LocalCache.getOrLoad(LocalCache.java:4004) at org.spark_project.guava.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4874) at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator$.compile(CodeGenerator.scala:1369) at org.apache.spark.sql.catalyst.expressions.codegen.GenerateSafeProjection$.create(GenerateSafeProjection.scala:197) at org.apache.spark.sql.catalyst.expressions.codegen.GenerateSafeProjection$.create(GenerateSafeProjection.scala:36) at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator.generate(CodeGenerator.scala:1325) at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator.generate(CodeGenerator.scala:1322) at org.apache.spark.sql.execution.DeserializeToObjectExec$$anonfun$2.apply(objects.scala:90) at org.apache.spark.sql.execution.DeserializeToObjectExec$$anonfun$2.apply(objects.scala:89) at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndexInternal$1$$anonfun$apply$24.apply(RDD.scala:818) at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndexInternal$1$$anonfun$apply$24.apply(RDD.scala:818) at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324) at org.apache.spark.rdd.RDD.iterator(RDD.scala:288) at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324) at org.apache.spark.rdd.RDD.iterator(RDD.scala:288) at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87) at org.apache.spark.scheduler.Task.run(Task.scala:109) at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:345) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 50, Column 16: failed to compile: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 50, Column 16: No applicable constructor/method found for actual parameters "org.apache.spark.unsafe.types.UTF8String"; candidates are: "public void sparkSQL.Tweet.setId(long)" at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator$.org$apache$spark$sql$catalyst$expressions$codegen$CodeGenerator$$doCompile(CodeGenerator.scala:1435) at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator$$anon$1.load(CodeGenerator.scala:1497) at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator$$anon$1.load(CodeGenerator.scala:1494) at org.spark_project.guava.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3599) at org.spark_project.guava.cache.LocalCache$Segment.loadSync(LocalCache.java:2379)
当我仔细观察时，我唯一提出的疑问是：
找不到适用于实际参数“ org.apache.spark.unsafe.types.UTF8String”的适用构造函数/方法；候选者为：“ public void sparkSQL.Tweet.setId（long）”
正如@ user9718686所写，id字段具有不同的类型：String在json文件和long类定义中。当您将其读Dataset<Row>入时，Spark会从文件中推断出模式并检测到id是类型String，这就是为什么当您尝试打印它时它可以工作的原因（正如您在注释中要求的那样）。如果要将数据框设置为Dataset<Tweet>，则必须将json文件更改为使用longid代替，String或者在尝试对数据框执行任何操作操作时，可以让Spark强制转换此id 。
String
long
Dataset<Row>
Dataset<Tweet>
Dataset<Row> rowDataset = sc.read().json("path"); Dataset<Tweet> tweetDataset = rowDataset .withColumn("id", rowDataset.col("id").cast(DataTypes.LongType)) .as(Encoders.bean(Tweet.class)); tweetDataset.printSchema(); System.out.println(tweetDataset.head().getId());
