Merge branch 'feature/PR85' into develop

pom.xml

@@ -3,7 +3,7 @@
   <groupId>org.bsc.maven</groupId>
   <artifactId>maven-processor-plugin-parent</artifactId>
   <packaging>pom</packaging>
-  <version>4.2</version>
+  <version>4.3-SNAPSHOT</version>
   <name>MAVEN PROCESSOR PLUGIN PARENT</name>
   <description>A maven plugin to process annotation for jdk6 at compile time
 

processor/pom.xml

@@ -13,7 +13,7 @@ This plugin could be considered the 'alter ego' of maven apt plugin http://mojo.
   <parent>
       <groupId>org.bsc.maven</groupId>
       <artifactId>maven-processor-plugin-parent</artifactId>
-      <version>4.2</version>
+      <version>4.3-SNAPSHOT</version>
   </parent>
 
   <properties>

processor/src/main/java/org/bsc/maven/plugin/processor/AbstractAnnotationProcessorMojo.java

@@ -54,7 +54,13 @@
 import java.nio.charset.Charset;
 import java.nio.charset.IllegalCharsetNameException;
 import java.nio.charset.UnsupportedCharsetException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.*;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Consumer;
@@ -269,6 +275,15 @@ public abstract class AbstractAnnotationProcessorMojo extends AbstractMojo
     @Parameter(defaultValue = "false", property = "fork")
     protected boolean fork;
 
+    /**
+     * Set this to true to skip annotation processing when there are no changes in the source files
+     * compared to the generated files.
+     *
+     * @since 4.3
+     */
+    @Parameter(defaultValue = "false", property = "skipSourcesUnchangedAnnotationProcessing")
+    protected boolean skipSourcesUnchanged;
+
     /**
      * Maven Session
      * 
@@ -557,6 +572,33 @@ private  List<String>  prepareOptions( JavaCompiler compiler ) {
 
     }
 
+    private boolean isSourcesUnchanged( List<JavaFileObject> allSources ) throws IOException {
+        long maxSourceDate = allSources.stream().map(JavaFileObject::getLastModified).max(Long::compare).get();
+
+        // use atomic long for effectively final wrapper around long variable
+        final AtomicLong maxOutputDate = new AtomicLong(Long.MIN_VALUE);
+
+        Files.walkFileTree(outputDirectory.toPath(), new SimpleFileVisitor<>() {
+            @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
+                    throws IOException
+            {
+                if(Files.isRegularFile(file)) {
+                    maxOutputDate.updateAndGet(t -> Math.max(t, file.toFile().lastModified()));
+                }
+                return FileVisitResult.CONTINUE;
+            }
+        });
+
+        if(getLog().isDebugEnabled())
+        {
+            getLog().debug("max source file date: " + maxSourceDate + ", max output date: " + maxOutputDate
+                    .get());
+        }
+
+        return maxSourceDate <= maxOutputDate.get();
+
+    }
+
     private void executeWithExceptionsHandled() throws Exception
     {
         if (outputDirectory == null)
@@ -755,6 +797,10 @@ private void executeWithExceptionsHandled() throws Exception
                 return;
             }
 
+            if(skipSourcesUnchanged && isSourcesUnchanged(allSources)) {
+                getLog().info( "no source file(s) change(s) detected! Processor task will be skipped");
+                return;
+            }
             final List<String> options = prepareOptions( compiler );
 
             final CompilationTask task = compiler.getTask(

test/pom.xml

@@ -11,7 +11,7 @@
     <parent>
         <groupId>org.bsc.maven</groupId>
         <artifactId>maven-processor-plugin-parent</artifactId>
-        <version>4.2</version>
+        <version>4.3-SNAPSHOT</version>
     </parent>
 
   <dependencies>

utils/pom.xml

@@ -31,7 +31,7 @@
     <parent>
         <groupId>org.bsc.maven</groupId>
         <artifactId>maven-processor-plugin-parent</artifactId>
-        <version>4.2</version>
+        <version>4.3-SNAPSHOT</version>
     </parent>
 
     <properties>