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Add JPMS ServiceLoader Support with Multi-Release JAR (#500)
* #426 Add JPMS module support with ServiceLoader **Note:** This is not a complete solution as handling of JDK 8 compatibility is outstanding. Currently, the fix would break usage of JDK 8. Enable `exec:java`-goal to execute Java applications using the Java Platform Module System (JPMS) with proper ServiceLoader support. Changes: - Split execution logic into classpath and module-path modes - Detect module syntax (module/class) in mainClass parameter - Create ModuleLayer with resolveAndBind() to include service providers - Use ModuleLayer.Controller to open packages for reflective access - Set thread context classloader to module's classloader The plugin now properly handles: - Module-path execution when `mainClass` uses "module/class" syntax - ServiceLoader provider discovery and binding in modular applications - Reflective access to main methods in unexported packages - Mixed module and classpath dependencies Integration test mexec-gh-426 validates the ServiceLoader functionality with a multi-module JPMS application (contract, provider, consumer). Technical implementation: - Use Configuration.resolveAndBind() instead of resolve() to include service providers declared with "uses" in module-info - Obtain ModuleLayer.Controller to programmatically open packages via addOpens() for reflective main method invocation - Load classes through the module layer's ClassLoader to maintain proper module isolation and visibility The fix was created in the course of support-and-care/maven-support-and-care#138. * #426 Fix JSR-512 main method detection This commit fixes two issues that caused build failures in GitHub: 1. JSR-512 Main Method Detection Problem: Tests failed with error: "The specified mainClass doesn't contain a main method with appropriate signature" JSR-512 (Java 21+) allows flexible main methods that can be non-public and instance methods. The original code used getMethod() which only finds PUBLIC methods, causing it to fail when searching for package-private main methods. Solution: - Changed from getMethod() to getDeclaredMethod() for JSR-512 - Added setAccessible(true) for non-public method invocation - Created findMethod() helper that searches class hierarchy - Validates return type is void (JSR-512 requirement) - Maintains correct priority order: 1. static void main(String[]) - traditional 2. static void main() - JSR-512 static no-args 3. void main(String[]) - JSR-512 instance with args 4. void main() - JSR-512 instance no-args 2. SystemExitException Logging Problem: Integration tests expected [ERROR] log prefix for SystemExitException but it was missing. When SystemExitException was thrown during method invocation, it got wrapped in InvocationTargetException and bypassed the logging code. Solution: - Added special handling in InvocationTargetException catch - Detects SystemExitException in the cause chain - Logs with appropriate level (ERROR for non-zero exit codes) - Re-throws the exception to maintain expected behavior * #426 Create Multi-Release Jar * #426 Move common ExecJava code to base class * #494 Find classic main method even if private
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‎pom.xml‎

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<invoker.parallelThreads>1C</invoker.parallelThreads>
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<project.build.outputTimestamp>2025-10-05T19:10:54Z</project.build.outputTimestamp>
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<maven-toolchains-plugin.version>3.2.0</maven-toolchains-plugin.version>
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<mojo.java.target>8</mojo.java.target>
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</properties>
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<dependencies>
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<configuration>
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<proc>none</proc>
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</configuration>
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<executions>
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<execution>
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<id>default-testCompile</id>
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<goals>
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<goal>testCompile</goal>
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</goals>
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<phase>test-compile</phase>
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<configuration>
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<parameters>true</parameters>
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</configuration>
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</execution>
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</executions>
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</plugin>
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<plugin>
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<groupId>org.codehaus.mojo</groupId>
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<artifactId>animal-sniffer-maven-plugin</artifactId>
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<configuration>
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<skip>true</skip>
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<signature>
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<groupId>org.codehaus.mojo.signature</groupId>
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<artifactId>java18</artifactId>
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</build>
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<profiles>
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<profile>
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<!-- Multi-Release JAR: Compile Java 9+ specific code when JDK 9+ is available -->
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<id>java9-mrjar</id>
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<activation>
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<jdk>[9,)</jdk>
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</activation>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<executions>
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<!-- Compile Java 9+ specific code -->
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<execution>
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<id>java9-compile</id>
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<goals>
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<goal>compile</goal>
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</goals>
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<phase>compile</phase>
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<configuration>
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<release>9</release>
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<compileSourceRoots>
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<compileSourceRoot>${project.basedir}/src/main/java9</compileSourceRoot>
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</compileSourceRoots>
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<outputDirectory>${project.build.outputDirectory}/META-INF/versions/9</outputDirectory>
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</configuration>
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</execution>
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<!-- Test compilation with parameters enabled -->
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<execution>
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<id>default-testCompile</id>
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<goals>
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<goal>testCompile</goal>
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</goals>
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<phase>test-compile</phase>
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<configuration>
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<source>9</source>
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<target>9</target>
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<parameters>true</parameters>
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</configuration>
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</execution>
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</executions>
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</plugin>
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</plugins>
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</build>
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</profile>
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<profile>
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<!-- JDK 8: Use simplified test compilation -->
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<id>java8-tests</id>
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<activation>
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<jdk>1.8</jdk>
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</activation>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<executions>
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<execution>
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<id>default-testCompile</id>
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<goals>
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<goal>testCompile</goal>
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</goals>
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<phase>test-compile</phase>
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<configuration>
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<source>8</source>
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<target>8</target>
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<parameters>true</parameters>
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</configuration>
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</execution>
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</executions>
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</plugin>
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</plugins>
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</build>
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</profile>
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<profile>
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<!-- workaround for concurrent access to local repository on Windows -->
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<!-- https://issues.apache.org/jira/browse/MRESOLVER-372 -->

‎src/it/projects/mexec-gh-426/consumer/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>java_module-serviceloader</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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</parent>
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<artifactId>consumer</artifactId>
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<dependencies>
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<dependency>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>contract</artifactId>
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<version>${project.version}</version>
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</dependency>
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<dependency>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>provider</artifactId>
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<version>${project.version}</version>
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<scope>runtime</scope>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.codehaus.mojo</groupId>
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<artifactId>exec-maven-plugin</artifactId>
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<version>@project.version@</version>
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<configuration>
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<mainClass>consumer/org.example.consumer.App</mainClass>
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</configuration>
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<executions>
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<execution>
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<id>test-jpms-serviceloader</id>
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<phase>integration-test</phase>
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<goals>
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<goal>java</goal>
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</goals>
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</execution>
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</executions>
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</plugin>
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</plugins>
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</build>
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</project>

‎src/it/projects/mexec-gh-426/consumer/src/main/java/module-info.java‎

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module consumer {
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requires contract;
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uses org.example.api.Greeter;
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}

‎src/it/projects/mexec-gh-426/consumer/src/main/java/org/example/consumer/App.java‎

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package org.example.consumer;
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import java.util.ServiceLoader;
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import org.example.api.Greeter;
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public class App {
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public static void main(String[] args) {
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ServiceLoader<Greeter> loader = ServiceLoader.load(Greeter.class);
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Greeter greeter = loader.findFirst()
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.orElseThrow(() -> new RuntimeException("No Greeter service provider found"));
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String message = greeter.greet("World");
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System.out.println(message);
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}
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}

‎src/it/projects/mexec-gh-426/contract/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>java_module-serviceloader</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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</parent>
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<artifactId>contract</artifactId>
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</project>

‎src/it/projects/mexec-gh-426/contract/src/main/java/module-info.java‎

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module contract {
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exports org.example.api;
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}

‎src/it/projects/mexec-gh-426/contract/src/main/java/org/example/api/Greeter.java‎

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package org.example.api;
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public interface Greeter {
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String greet(String name);
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}

‎src/it/projects/mexec-gh-426/invoker.properties‎

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invoker.goals = clean install
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invoker.java.version = 11+
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invoker.buildResult = success

‎src/it/projects/mexec-gh-426/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>java_module-serviceloader</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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<packaging>pom</packaging>
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<name>JPMS ServiceLoader Test</name>
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<description>Test exec:java with Java Module System and ServiceLoader</description>
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<modules>
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<module>contract</module>
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<module>provider</module>
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<module>consumer</module>
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</modules>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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</properties>
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<build>
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<pluginManagement>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.13.0</version>
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<configuration>
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<release>11</release>
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</configuration>
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</plugin>
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</plugins>
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</pluginManagement>
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</build>
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</project>

‎src/it/projects/mexec-gh-426/provider/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>java_module-serviceloader</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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</parent>
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<artifactId>provider</artifactId>
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<dependencies>
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<dependency>
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<groupId>org.codehaus.mojo.exec.it</groupId>
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<artifactId>contract</artifactId>
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<version>${project.version}</version>
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</dependency>
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</dependencies>
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</project>

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