[#323] add java executable recognition.

- added two ITs to check true/false behaviour of the new parameter.

src/it/projects/mexec-323-force-java/invoker.properties

@@ -0,0 +1,3 @@
+invoker.goals = compile
+invoker.debug = true
+invoker.os.family = !windows

src/it/projects/mexec-323-force-java/pom.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.codehaus.mojo.exec.it</groupId>
+    <artifactId>parent</artifactId>
+    <version>0.1</version>
+  </parent>
+
+  <artifactId>mexec-323</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+  <packaging>pom</packaging>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>exec-maven-plugin</artifactId>
+        <version>@pom.version@</version>
+        <executions>
+          <execution>
+            <phase>compile</phase>
+            <goals>
+              <goal>exec</goal>
+            </goals>
+            <configuration>
+              <executable>echo</executable>
+              <forceJava>true</forceJava>
+              <arguments>
+                <argument>--</argument>
+                <argument>-p</argument>
+                <argument>dist/emails</argument>
+              </arguments>
+              <workingDirectory>src/build</workingDirectory>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+
+</project>

src/it/projects/mexec-323-force-java/verify.groovy

@@ -0,0 +1,22 @@
+/*
+ * 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.
+ */
+def log = new File( basedir, "build.log" )
+assert log.exists()
+// missing dist/emails here
+assert log.text.contains( "Executing command line: [echo, --, -p]" )

src/it/projects/mexec-323/invoker.properties

@@ -1,2 +1,3 @@
 invoker.goals = compile
 invoker.debug = true
+invoker.os.family = !windows

src/it/projects/mexec-323/verify.groovy

@@ -0,0 +1,25 @@
+/*
+ * 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.
+ */
+def createdDir = new File(basedir, "src/build/dist/emails")
+assert createdDir.exists()
+assert createdDir.isDirectory()
+
+File log = new File(basedir, 'build.log')
+assert log.exists()
+assert log.getText().contains( "Executing command line: [mkdir, -p, dist/emails]" )

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

@@ -42,6 +42,7 @@
 import java.util.jar.JarEntry;
 import java.util.jar.JarOutputStream;
 import java.util.jar.Manifest;
+import java.util.regex.Pattern;
 
 import org.apache.commons.exec.CommandLine;
 import org.apache.commons.exec.ExecuteException;
@@ -83,6 +84,12 @@
 public class ExecMojo
     extends AbstractExecMojo
 {
+
+    /**
+     * Trying to recognize whether the given {@link #executable} might be a {@code java} binary.
+     */
+    private static final Pattern ENDS_WITH_JAVA = Pattern.compile( "^.*java(\\.exe|\\.bin)?$", Pattern.CASE_INSENSITIVE );
+
     /**
      * <p>
      * The executable. Can be a full path or the name of the executable. In the latter case, the executable must be in
@@ -313,6 +320,18 @@ public class ExecMojo
     @Parameter( property = "exec.longModulepath", defaultValue = "true" )
     private boolean longModulepath;
 
+    /**
+     * Forces the plugin to recognize the given executable as java executable. This helps with {@link #longClasspath}
+     * and {@link #longModulepath} parameters.
+     *
+     * <p>You shouldn't normally be needing this unless you renamed your java binary or are executing tools
+     * other than {@code java} which need modulepath or classpath parameters in a separate file.</p>
+     *
+     * @since 3.1.1
+     */
+    @Parameter (property = "exec.forceJava", defaultValue = "false" )
+    private boolean forceJava;
+
     /**
      * If set to true the child process executes asynchronously and build execution continues in parallel.
      */
@@ -727,12 +746,35 @@ boolean isResultCodeAFailure( int result )
 
     private boolean isLongClassPathArgument( String arg )
     {
-        return longClasspath && ( "-classpath".equals( arg ) || "-cp".equals( arg ) );
+        return isJavaExec() && longClasspath && ( "-classpath".equals( arg ) || "-cp".equals( arg ) );
     }
 
     private boolean isLongModulePathArgument( String arg )
     {
-        return longModulepath && ( "--module-path".equals( arg ) || "-p".equals( arg ) );
+        return isJavaExec() && longModulepath && ( "--module-path".equals( arg ) || "-p".equals( arg ) );
+    }
+
+    /**
+     * Returns {@code true} when a java binary is being executed.
+     *
+     * @return {@code true} when a java binary is being executed.
+     */
+    private boolean isJavaExec()
+    {
+        if ( forceJava )
+        {
+            return true;
+        }
+
+        if ( this.executable.contains( "%JAVA_HOME" )
+                || this.executable.contains( "${JAVA_HOME}" )
+                || this.executable.contains( "$JAVA_HOME" ) )
+        {
+            // also applies to *most* other tools.
+            return true;
+        }
+
+        return ENDS_WITH_JAVA.matcher( this.executable ).matches();
     }
 
     /**