'Compile and execute a JDK preview feature with Maven

With JDK/12 EarlyAccess Build 10, the JEP-325 Switch Expressions has been integrated as a preview feature in the JDK. A sample code for the expressions (as in the JEP as well):

Scanner scanner = new Scanner(System.in);
Day day = Day.valueOf(scanner.next());
switch (day) {
    case MONDAY, TUESDAY -> System.out.println("Back to work.") ;
    case WEDNESDAY -> System.out.println("Wait for the end of week...") ;
    case THURSDAY,FRIDAY -> System.out.println("Plan for the weekend?");
    case SATURDAY, SUNDAY -> System.out.println("Enjoy the holiday!");
}

where Day being an enum as 

public enum Day {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
}

The Preview Language and VM Features JEP-12 already elaborate how a feature can be enabled during compile and runtime using javac and java.

How can one try out this feature using Maven?

javamavenswitch-statementjava-12preview-featuregoogle-cloud-platformgoogle-cloud-functionsgoogle-workflows


Solution 1:[1]

To enable preview feature you must define --enable-preview in pom.xml under compilerArgs

in below I mention how to enable preview feature with java 13.

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.8.0</version>
      <configuration>
        <release>13</release>
        <compilerArgs>
          --enable-preview
        </compilerArgs>
      </configuration>
    </plugin>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>3.0.0-M3</version>
      <configuration>
        <argLine>--enable-preview</argLine>
      </configuration>
    </plugin>
  </plugins>
 </build>

Solution 2:[2]

Since version 3.10.1 of the Maven Compiler Plugin, there is a dedicated parameter for enabling preview features:

<enablePreview>

Set to true to Enable preview language features of the java compiler

  • Type: boolean
  • Since: 3.10.1
  • Required: No
  • User Property: maven.compiler.enablePreview
  • Default: false

Example:

<plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.10.1</version>
    <configuration>
        <release>${java.version}</release>
        <enablePreview>true</enablePreview>
    </configuration>
</plugin>

Solution 3:[3]

This must be added in the workflow code:

auth:
    type: OIDC

See https://cloud.google.com/workflows/docs/calling-run-functions?authuser=1#add_auth_info

Sources

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Source: Stack Overflow

Solution Source
Solution 1
Solution 2 beatngu13
Solution 3 user3205999

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