Foreach runs on the executors and so is not able to modify an array list
that is only present on the driver. You should just call collectAsList on
the DataFrame.
On Mon, Apr 24, 2017 at 10:36 AM, Devender Yadav <
devender.ya...@impetus.co.in> wrote:
> Hi All,
>
>
> I am using Spark 1.6.2 and Java 7.
>
>
> *Sample json* (total 100 records):
>
> {"name":"dev","salary":10000,"occupation":"engg","address":"noida"}
>
> {"name":"karthik","salary":20000,"occupation":"engg","address":"noida"}
>
> *Useful code:*
>
> final List<Map<String,String>> jsonData = new ArrayList<>();
>
> DataFrame df =
> sqlContext.read().json("file:///home/dev/data-json/emp.json");
> JavaRDD<String> rdd = df.repartition(1).toJSON().toJavaRDD();
>
> rdd.foreach(new VoidFunction<String>() {
> @Override
> public void call(String line) {
> try {
> jsonData.add (new ObjectMapper().readValue(line, Map.class));
> System.out.println(Thread.currentThread().getName());
> System.out.println("List size: "+jsonData.size());
> } catch (IOException e) {
> e.printStackTrace();
> }
> }
> });
>
> System.out.println(Thread.currentThread().getName());
> System.out.println("List size: "+jsonData.size());
>
> jsonData List is empty in the end.
>
>
> Output:
>
> Executor task launch worker-1List size: 1Executor task launch worker-1List
> size: 2Executor task launch worker-1List size: 3...Executor task launch
> worker-1List size: 100
>
> mainList size: 0
>
>
>
> Regards,
> Devender
>
> ------------------------------
>
>
>
>
>
>
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