'force maven to use different java version

I have my existing project that uses Java 1.8 My JAVA_HOME is set to Java 1.8 As a result maven is using Java 1.8 , which is fine Now our project has decided to start using SonarQube 9.x which runs on Java 11 In addition to run any scan / analysis of our code - it needs Java 11 as well

So here is what I need to be doing :

#1 Compile code using default jdk ( 1.8 ) ( mvn clean install )

#2 Run sonar scan using jdk 11 ( mvn sonar:sonar )

To execute #2 need maven to use jdk 11 while to execute #1 need maven to use jdk 1.8.

After reading various questions on SO came across 'toolchain'

So added toolchains.xml into my 'm2' folder :

<?xml version="1.0" encoding="UTF-8"?>
<toolchains>
 <!-- JDK toolchains -->
 <toolchain>
  <type>jdk</type>
  <provides>
   <version>1.11</version>
   <vendor>sun</vendor>
  </provides>
  <configuration>
   <jdkHome>C:\construction\tools\jdk-11.0.12</jdkHome>
  </configuration>
</toolchain>
<toolchain>
 <type>jdk</type>
 <provides>
  <version>1.8</version>
  <vendor>sun</vendor>
 </provides>
 <configuration>
  <jdkHome>C:\Program Files\Java\jdk1.8.0_191</jdkHome>
 </configuration>
</toolchain>

Added toolchain plugin in my projects pom.xml

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-toolchains-plugin</artifactId>
            <version>1.1</version>
            <executions>
                <execution>
                    <goals>
                      <goal>toolchain</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <toolchains>
                    <jdk>
                        <version>1.11</version>
                        <vendor>sun</vendor>
                    </jdk>
                </toolchains>
            </configuration>
        </plugin>

Now when I run maven clean install can see in logs that java 11 'seems' to be used :

[INFO] --- maven-toolchains-plugin:1.1:toolchain (default) @ TreeSurveyAPI ---

[INFO] Required toolchain: jdk [ vendor='sun' version='1.11' ] [INFO] Found matching toolchain for type jdk: JDK[C:\construction\tools\jdk-11.0.12]

[INFO] --- maven-compiler-plugin:3.7.0:compile (default-compile) @ TreeSurveyAPI --- [INFO] Toolchain in maven-compiler-plugin: JDK[C:\construction\tools\jdk-11.0.12] [INFO] Changes detected - recompiling the module! [INFO] Compiling 11 source files to C:\construction\xxx\XYZ-main\target\classes

So it 'seems' that maven along with toolchain is using Java 11 to compile the code . However after executing javap against compiled class file indicates Major version as 52 ( Java 8 )

javap -verbose Abc.class | findstr "major"

So here are my questions :

#1 in the above case since toolchain points to java 11 shouldnt the code be compiled with java 11 ? why is it using java 8 ?

#2 How can I conditionally use java 8 Vs java 11 ( compile and build using java 8 and run sonar task using java 11 ) ?

Thanks

javamavensonarqubemaven-toolchains-plugin


Solution 1:[1]

You can run your project on java 11 also. It will run java 8 code no problem for 99% of the cases. This is what I would do. Therefore, upgrading the projects java version seems to be the easiest solution.

If this does not work, check out this answer

Also, if you need to be able to quickly change JVM versions for various tasks and in various folders, you can use this tool

Sources

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Source: Stack Overflow

Solution Source
Solution 1

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