Hi,
I have both JDK 8 and 14 on my system and yesterday I ran into this
exception (I put the info I have in this ticket
https://issues.apache.org/jira/browse/FLINK-18455 ) :
java.lang.NoSuchMethodError:
java.nio.ByteBuffer.position(I)Ljava/nio/ByteBuffer;
>From digging around (
https://stackoverflow.com/questions/61267495/exception-in-thread-main-java-lang-nosuchmethoderror-java-nio-bytebuffer-flip
)
it seems this is caused when using JDK 9+ without setting '-release 8' and
then running with JDK 8.
Essentially there are two solutions I see a lot:
1) Add the -release 8 flag to the compiler
2) Use the flaky workaround to cast all problem cases to the superclass
implementing the method (i.e. cast to java.nio.Buffer)
Looking at the actual Flink code I found that
In a JDK 8 build both source and target are set to Java 8
https://github.com/apache/flink/blob/d735d8cd8e5d9fae5322001099097581822453ae/pom.xml#L109
<java.version>1.8</java.version>
https://github.com/apache/flink/blob/d735d8cd8e5d9fae5322001099097581822453ae/pom.xml#L115
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
In a JDK 11 build a profile is activated that overrides it to Java 11
https://github.com/apache/flink/blob/d735d8cd8e5d9fae5322001099097581822453ae/pom.xml#L938
<profile>
<id>java11</id>
<activation>
<jdk>11</jdk>
https://github.com/apache/flink/blob/d735d8cd8e5d9fae5322001099097581822453ae/pom.xml#L1004
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>11</source>
<target>11</target>
So when building with Java 11 the output classes are Java 11 compatible
binaries.
However I have Java 14 (and the 'java11' profile is only activated at the
EXACT version of java 11) so it stays at source and target 1.8 but does not
specify the "release 8" setting. ... which causes the problems I see.
Looking at the current build settings I was puzzled a bit and I have this
main question:
What is the Java version Apache Flink is supposed to work with?
Currently I would expect Java 8.
So what I propose for this problem as a fix is to set source, target and
release to Java 8 for all compiler versions (i.e. also Java 9, 11, 14, ...).
That way you can use any compiler and get the correct results.
I also am curious if that would fix the tests that seem to fail under Java
11.
What do you think is the correct approach for this?
--
Best regards / Met vriendelijke groeten,
Niels Basjes
