Ensure maven.properties can be forwarded to system properties for exec:java

src/main/java/org/codehaus/mojo/exec/AbstractProperty.java

@@ -0,0 +1,27 @@
+package org.codehaus.mojo.exec;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * Base type for system properties.
+ */
+public class AbstractProperty
+{
+}

src/main/java/org/codehaus/mojo/exec/ExecJavaMojo.java

@@ -18,6 +18,7 @@
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.ForkJoinPool;
+import java.util.stream.Stream;
 
 import org.apache.maven.artifact.Artifact;
 import org.apache.maven.artifact.resolver.ArtifactResolutionException;
@@ -94,7 +95,7 @@ public class ExecJavaMojo
      * @since 1.0
      */
     @Parameter
-    private Property[] systemProperties;
+    private AbstractProperty[] systemProperties;
 
     /**
      * Indicates if mojo should be kept running after the mainclass terminates. Use full for server like apps with
@@ -542,14 +543,29 @@ private Collection<Thread> getActiveThreads( ThreadGroup threadGroup )
      */
     private void setSystemProperties()
     {
-        if ( systemProperties != null )
+        if ( systemProperties == null )
         {
-            originalSystemProperties = System.getProperties();
-            for ( Property systemProperty : systemProperties )
+            return;
+        }
+        // copy otherwise the restore phase does nothing
+        originalSystemProperties = new Properties();
+        originalSystemProperties.putAll(System.getProperties());
+
+        if ( Stream.of( systemProperties ).anyMatch( it -> it instanceof ProjectProperties ) )
+        {
+            System.getProperties().putAll( project.getProperties() );
+        }
+
+        for ( AbstractProperty systemProperty : systemProperties )
+        {
+            if ( ! ( systemProperty instanceof  Property ) )
             {
-                String value = systemProperty.getValue();
-                System.setProperty( systemProperty.getKey(), value == null ? "" : value );
+                continue;
             }
+
+            Property prop = (Property) systemProperty;
+            String value = prop.getValue();
+            System.setProperty( prop.getKey(), value == null ? "" : value );
         }
     }
 

src/main/java/org/codehaus/mojo/exec/ProjectProperties.java

@@ -0,0 +1,27 @@
+package org.codehaus.mojo.exec;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * Represents all project properties (to set as system properties).
+ */
+public class ProjectProperties extends AbstractProperty
+{
+}

src/main/java/org/codehaus/mojo/exec/Property.java

@@ -24,7 +24,7 @@
  * 
  * @author Kaare Nilsen ([email protected])
  */
-public class Property
+public class Property extends AbstractProperty
 {
     private String key;
 

src/main/java/org/codehaus/mojo/exec/SystemProperty.java

@@ -0,0 +1,27 @@
+package org.codehaus.mojo.exec;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * Just to comply to maven configuration (object converter) and the legacy configuration.
+ */
+public class SystemProperty extends Property
+{
+}

src/site/apt/examples/example-java-project-properties.apt.vm

@@ -0,0 +1,71 @@
+ ------
+ Forward maven properties to exec:java goal
+ ------
+ Romain Manni-Bucau
+ ------
+ 2022-11-14
+ ------
+
+ ~~ Copyright 2022 The Codehaus
+ ~~
+ ~~ Licensed under the Apache License, Version 2.0 (the "License");
+ ~~ you may not use this file except in compliance with the License.
+ ~~ You may obtain a copy of the License at
+ ~~
+ ~~      http://www.apache.org/licenses/LICENSE-2.0
+ ~~
+ ~~ Unless required by applicable law or agreed to in writing, software
+ ~~ distributed under the License is distributed on an "AS IS" BASIS,
+ ~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ ~~ See the License for the specific language governing permissions and
+ ~~ limitations under the License.
+
+ ~~ NOTE: For help with the syntax of this file, see:
+ ~~ http://maven.apache.org/doxia/references/apt-format.html
+
+
+You can ensure the maven properties are available to your main forcing `<projectProperties />` property type.
+
+  Tip: you can still override potentially conflicting properties if you set them *after*.
+
+* pom.xml
+
+-------------------
+<project>
+  ...
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>exec-maven-plugin</artifactId>
+        <version>${project.version}</version>
+        <executions>
+          <execution>
+            ...
+            <goals>
+              <goal>java</goal>
+            </goals>
+          </execution>
+        </executions>
+        <configuration>
+          <mainClass>com.example.Main</mainClass>
+          <arguments>
+            <argument>argument1</argument>
+            ...
+          </arguments>
+          <systemProperties>
+            <projectProperties />
+            <systemProperty>
+              <key>myproperty</key>
+              <value>myvalue</value>
+            </systemProperty>
+            ...
+          </systemProperties>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+   ...
+</project>
+-------------------
+

src/site/apt/index.apt

@@ -70,3 +70,5 @@ Exec Maven Plugin
   * {{{./examples/example-exec-using-toolchains.html} Using toolchains instead of explicit paths}}
 
   * {{{./examples/example-exec-using-executabledependency.html} Using executable binary dependencies instead of local executables}}
+
+  * {{{./examples/example-java-project-properties.html} Forward maven system properties to the main}}

src/test/java/org/codehaus/mojo/exec/ExecJavaMojoTest.java

@@ -85,11 +85,12 @@ public void testEmptySystemProperty()
     {
         File pom = new File( getBasedir(), "src/test/projects/project5/pom.xml" );
 
-        assertNull( "System property not yet created", System.getProperty( "project5.property.with.no.value" ) );
+        assertNull( "System property not yet created", System.getProperty( "test.name" ) );
 
-        execute( pom, "java" );
+        assertEquals( "Hello " + System.lineSeparator(), execute( pom, "java" ) );
 
-        assertEquals( "System property now empty", "", System.getProperty( "project5.property.with.no.value" ) );
+        // ensure we get back in the original state and didn't leak the execution config
+        assertNull( "System property not yet created", System.getProperty( "test.name" ) );
     }
 
     /**
@@ -275,6 +276,21 @@ public void testExcludedClasspathElement() throws Exception
         }
     }
 
+    /**
+     * Ensure all project properties can be forwarded to the execution as system properties.
+     *
+     * @throws Exception if any exception occurs
+     */
+    public void testProjectProperties()
+            throws Exception
+    {
+        File pom = new File( getBasedir(), "src/test/projects/project18/pom.xml" );
+
+        String output = execute( pom, "java" );
+
+        assertEquals( "Hello project18 project" + System.lineSeparator(), output );
+    }
+
     /**
      * @return output from System.out during mojo execution
      */

src/test/java/org/codehaus/mojo/exec/HelloSystemProperty.java

@@ -0,0 +1,18 @@
+package org.codehaus.mojo.exec;
+
+/**
+ * Simple class with a main method reading a system property
+ */
+public class HelloSystemProperty
+{
+    /**
+     * Print on stdout hello and the system property test.name value.
+     * 
+     * @param args the arguments
+     */
+    public static void main( String... args )
+    {
+        // important: do not default on empty due to testEmptySystemProperty()
+        System.out.println( "Hello " + System.getProperty( "test.name" ) );
+    }
+}

src/test/projects/project18/pom.xml

@@ -0,0 +1,48 @@
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>org.cb.maven.plugins.exec</groupId>
+  <artifactId>project18</artifactId>
+  <version>0.1</version>
+  <packaging>jar</packaging>
+  <name>Maven Exec Plugin</name>
+  <inceptionYear>2005</inceptionYear>
+
+  <licenses>
+    <license>
+      <name>Apache License 2</name>
+      <url>http://www.apache.org/licenses/LICENSE-2.0.txt</url>
+      <distribution>repo</distribution>
+    </license>
+  </licenses>
+
+  <properties>
+    <test.name>${project.artifactId} project</test.name>
+  </properties>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>exec-maven-plugin</artifactId>
+        <executions>
+           <execution>
+              <phase>test</phase>
+              <goals>
+                 <goal>java</goal>
+              </goals>
+           </execution>
+        </executions>
+        <configuration>
+          <mainClass>org.codehaus.mojo.exec.HelloSystemProperty</mainClass>
+          <additionalClasspathElements>
+            <additionalClasspathElements>../../../../target/test-classes</additionalClasspathElements> <!-- test setup requires it -->
+          </additionalClasspathElements>
+          <systemProperties>
+            <projectProperties />
+          </systemProperties>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+
+</project>

src/test/projects/project5/pom.xml

@@ -28,10 +28,10 @@
            </execution>
         </executions>
         <configuration>
-          <mainClass>org.codehaus.mojo.exec.DummyMain</mainClass>
+          <mainClass>org.codehaus.mojo.exec.HelloSystemProperty</mainClass>
           <systemProperties>
             <property>
-              <key>project5.property.with.no.value</key>
+              <key>test.name</key>
               <value></value>
             </property>
             <property>