Hello,
I am trying to use Java 8 lambdas in my project and hit the following
error:
Exception in thread "main"
org.apache.flink.api.common.functions.InvalidTypesException: The
generic type parameters of 'Tuple2' are missing.
It seems that your compiler has not stored them into the .class
file.
Currently, only the Eclipse JDT compiler preserves the type
information necessary to use the lambdas feature type-safely.
See the documentation for more information about how to compile jobs
containing lambda expressions.
at
org.apache.flink.api.java.typeutils.TypeExtractor.validateLambdaGenericParameter(TypeExtractor.java:779)
at
org.apache.flink.api.java.typeutils.TypeExtractor.validateLambdaGenericParameters(TypeExtractor.java:765)
at
org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:135)
at
org.apache.flink.api.java.typeutils.TypeExtractor.getMapReturnTypes(TypeExtractor.java:78)
at org.apache.flink.api.java.DataSet.map(DataSet.java:160)
at eu.euranova.flink.Axa.main(Axa.java:62)
My very simple code is the following:
File directory = new File(
"PATH TO A DIRECTORY WITH CSV FILES");
DataSet set = env.fromElements(new Tuple3(0, 0.0, 0.0));
for (File file : directory.listFiles()) {
int pathID = 0;
String filePath = "file://" + file.getAbsolutePath();
DataSet set2 =
env.readCsvFile(filePath).ignoreFirstLine().includeFields("11").types(Double.class,Double.class);
DataSet set3 = set2.map(tuple -> new Tuple3(pathID, tuple.f0,
tuple.f1));
set = set.union(set3);
}
I followed the steps in the Java 8 documentation section
(http://flink.apache.org/docs/0.8/java8_programming_guide.html#compiler-limitations)
and have applied the following to the pom.xml file created using the
flink archetype:
- Modified java 1.6 reference to 1.8
- Uncommented the section related to Java 8 lambdas
- Installed Eclipse Java developer tools (JDT)
- Installed m2e-jdt connector
The pom.xml does not show any error and builds fine.
Am I missing something? Do I need to explicity set up Eclipse JDT? The
only installed environment shown in my preferences is the
/usr/java/jdk-1.8.0_31 from oracle.
Thanks and best regards,
Tran Nam-Luc
