[jira] [Commented] (FLINK-27549) Inconsistent bytecode version when enable jdk11 or higher version

["牛一凡 (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-27549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17959637#comment-17959637 ] 

牛一凡 commented on FLINK-27549:
-----------------------------

Hello, I think this issue is very clear. 
In fact, when I modified the <target.java.version>1.8</target.java.version> in the pom.xml of the root directory of the flink project to <target.java.version>17</target.java.version>, and compiled the 1.18 project based on jdk17, I encountered this error: 

 
{code:java}
[ERROR] scalac error: 'jvm-17' is not a valid choice for '-target'
[INFO]   scalac -help  gives more information
[ERROR] scalac error: bad option: '-target:jvm-17'
[ERROR] Failed to execute goal net.alchim31.maven:scala-maven-plugin:3.2.2:compile (default-cli) on project flink-annotations: wrap: org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1) -> [Help 1]
{code}
!image-2025-06-11-11-17-54-715.png!

The compilation command I used was:
mvn clean install -Dmaven.compiler.source=17 -Dmaven.compiler.target=17 -DskipTests -Dfast -Pskip-webui-build -T 1C
My JDK version is:
java version "17.0.15" 2025-04-15 LTS
Java(TM) SE Runtime Environment (build 17.0.15+9-LTS-241)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.15+9-LTS-241, mixed mode, sharing)

When I did not modify the pom.xml file, direct compilation based on the jdk17 environment was feasible, but at this time the java class and scala class bytecode versions I got were both jdk8. I wonder if the flink project can now be compiled based on jdk17 and get the correct bytecode version? It seems that once I hardcode the jdk version, my compilation will fail.

> Inconsistent bytecode version when enable jdk11 or higher version
> -----------------------------------------------------------------
>
>                 Key: FLINK-27549
>                 URL: https://issues.apache.org/jira/browse/FLINK-27549
>             Project: Flink
>          Issue Type: Bug
>          Components: API / Scala
>    Affects Versions: 1.14.4, 1.15.0
>            Reporter: Ran Tao
>            Priority: Major
>         Attachments: image-2025-06-11-11-17-54-715.png, screenshot-1.png, screenshot-2.png
>
>
> Current flink project build with jdk1.8 is ok.
> when enable jdk11, it has some scenarios.
> 1. Using jdk11 but source 1.8 target 1.8   it's ok.
> 2. Using jdk11 and with jdk11-target source 11 and target 11. build java ok. But the generated bytecode version of scala class is already 52(jdk8).  We can test with any of a scala class under jdk11 build result. e.g.
> {code:java}
> javap -verbose AggregateDataSet.class | grep major
> major version: 52
> {code}
> I have test many times and make conclusion that flink jdk11 now is not a completed and pure jdk11 version because of inconsistent bytecode version with java & scala. And it may cause some problems, for example:
> 1. inconsistent bytecode version between java & scala
> 2. Using reflection about class may generate some unkown errors
> 3. Runtime jdk11 environment can not optimize these lower bytecode.
> I have dipped into this problem and found out we must  upgrade scala to 2.13(2.11 & 2.12 only support generate bytecode version <=1.8). the 2.13 can support generate scala target 11 bytecode and higher and jdk8.
> We can see from scalac, the first is 2.12 the next is scala 2.13:
>  !screenshot-1.png! 
>  !screenshot-2.png! 
> By the way, even if scala-2.12 support generare 11 bytecode, current flink build also fail. Because the config about scala-maven-plugin is error, the correct format about jdk11 is target:11 not target:jvm-11, the latter format only for <=1.8 with scala-2.11 and 2.12.
> {code:java}
> <plugin>
> 					<groupId>net.alchim31.maven</groupId>
> 					<artifactId>scala-maven-plugin</artifactId>
> 					<version>3.2.2</version>
> 					<configuration>
> 						<args>
> 							<arg>-nobootcp</arg>
> 							<arg>-target:jvm-${target.java.version}</arg>
> 						</args>
> 						<jvmArgs>
> 							<arg>-Xss2m</arg>
> 						</jvmArgs>
> 					</configuration>
> 				</plugin>
> {code}
> I wonder current the community whether to support the completed jdk11 version? and  if not, at least we need to comment in pom or flink docs to let users know about this problem?



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