我正在尝试运行以下简单的Spark代码:
Gson gson = new Gson();
JavaRDD<String> stringRdd = jsc.textFile("src/main/resources/META-INF/data/supplier.json");
JavaRDD<SupplierDTO> rdd = stringRdd.map(new Function<String, SupplierDTO>()
{
private static final long serialVersionUID = -78238876849074973L;
@Override
public SupplierDTO call(String str) throws Exception
{
return gson.fromJson(str, SupplierDTO.class);
}
});
但是它在执行stringRdd.map语句时抛出以下错误：
org.apache.spark.SparkException: Task not serializable
at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:166)
at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:158)
at org.apache.spark.SparkContext.clean(SparkContext.scala:1478)
at org.apache.spark.rdd.RDD.map(RDD.scala:288)
at org.apache.spark.api.java.JavaRDDLike$class.map(JavaRDDLike.scala:78)
at org.apache.spark.api.java.JavaRDD.map(JavaRDD.scala:32)
at com.demo.spark.processor.cassandra.CassandraDataUploader.uploadData(CassandraDataUploader.java:71)
at com.demo.spark.processor.cassandra.CassandraDataUploader.main(CassandraDataUploader.java:47)
Caused by: java.io.NotSerializableException: org.apache.spark.api.java.JavaSparkContext
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:42)
at org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:73)
at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:164)
... 7 more
这里的“jsc”是我正在使用的< code>JavaSparkContext对象。据我所知，< code>JavaSparkContext不是一个< code>Serializable对象，我们不应该在任何将被发送给Spark workers的函数中使用它。
现在，我无法理解的是，JavaSparkContext的实例是如何发送给工人的？为了避免这种情况，我应该在代码中更改什么？
gson引用将外部类“拉”到闭包的范围内，并带有其完整的对象图。
在这种情况下，在闭包中创建gson对象：
public SupplierDTO call(String str) throws Exception {
Gson gson = Gson();
return gson.fromJson(str, SupplierDTO.class);
}
您还可以声明火花上下文＜code＞transient＜/code＞
如果创建 Gson 实例的成本很高，请考虑使用 mapPartitions 而不是 map。
对我来说，我使用以下选择之一解决了这个问题：
请参阅文档作业因阶段故障而中止：任务不可序列化
查看解决此问题的其他可用选项e
你可以用下面的代码代替第9行。(< code>return gson.fromJson(str，supplier dto . class)；)
return new Gson().fromJson(str, SupplierDTO.class);//this is correct
并删除第 1 行。（Gson gson = new Gson（）;）
