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https://issues.apache.org/jira/browse/FLINK-4872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15670710#comment-15670710
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Timo Walther commented on FLINK-4872:
-------------------------------------
I still can't reproduce your problem. What I noticed is that a POJO needs at
least one field and should be serializable in your example code. Your code
snippet works on my machine in local and cluster mode. Could you give more
information about your cluster? JVM Version, OS etc.?
> Type erasure problem exclusively on cluster execution
> -----------------------------------------------------
>
> Key: FLINK-4872
> URL: https://issues.apache.org/jira/browse/FLINK-4872
> Project: Flink
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.1.2
> Reporter: Martin Junghanns
>
> The following codes runs fine on local and collection execution environment
> but fails when executed on a cluster.
> {code:title=Problem.java}
> import org.apache.flink.api.common.functions.MapFunction;
> import org.apache.flink.api.java.DataSet;
> import org.apache.flink.api.java.ExecutionEnvironment;
> import org.apache.flink.api.java.tuple.Tuple1;
> import java.lang.reflect.Array;
> public class Problem {
> public static class Pojo {
> }
> public static class Foo<T> extends Tuple1<T> {
> }
> public static class Bar<T> extends Tuple1<T[]> {
> }
> public static class UDF<T> implements MapFunction<Foo<T>, Bar<T>> {
> private final Class<T> clazz;
> public UDF(Class<T> clazz) {
> this.clazz = clazz;
> }
> @Override
> public Bar<T> map(Foo<T> value) throws Exception {
> Bar<T> bar = new Bar<>();
> //noinspection unchecked
> bar.f0 = (T[]) Array.newInstance(clazz, 10);
> return bar;
> }
> }
> public static void main(String[] args) throws Exception {
> // runs in local, collection and cluster execution
> withLong();
> // runs in local and collection execution, fails on cluster execution
> withPojo();
> }
> public static void withLong() throws Exception {
> ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
> Foo<Long> foo = new Foo<>();
> foo.f0 = 42L;
> DataSet<Foo<Long>> barDataSource = env.fromElements(foo);
> DataSet<Bar<Long>> map = barDataSource.map(new UDF<>(Long.class));
> map.print();
> }
> public static void withPojo() throws Exception {
> ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
> Foo<Pojo> foo = new Foo<>();
> foo.f0 = new Pojo();
> DataSet<Foo<Pojo>> barDataSource = env.fromElements(foo);
> DataSet<Bar<Pojo>> map = barDataSource.map(new UDF<>(Pojo.class));
> map.print();
> }
> }
> {code}
> {code:title=ProblemTest.java}
> import org.apache.flink.test.util.MultipleProgramsTestBase;
> import org.junit.Test;
> import org.junit.runner.RunWith;
> import org.junit.runners.Parameterized;
> @RunWith(Parameterized.class)
> public class ProblemTest extends MultipleProgramsTestBase {
> public ProblemTest(TestExecutionMode mode) {
> super(mode);
> }
> @Test
> public void testWithLong() throws Exception {
> Problem.withLong();
> }
> @Test
> public void testWithPOJO() throws Exception {
> Problem.withPojo();
> }
> }
> {code}
> Exception:
> {code}
> The return type of function 'withPojo(Problem.java:58)' could not be
> determined automatically, due to type erasure. You can give type information
> hints by using the returns(...) method on the result of the transformation
> call, or by letting your function implement the 'ResultTypeQueryable'
> interface.
> org.apache.flink.api.java.DataSet.getType(DataSet.java:178)
> org.apache.flink.api.java.DataSet.collect(DataSet.java:407)
> org.apache.flink.api.java.DataSet.print(DataSet.java:1605)
> Problem.withPojo(Problem.java:60)
> Problem.main(Problem.java:38)
> {code}
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