Add the possibility to exclude some keys to write or/and generate (or not) the comment header with the timestamp

src/main/java/org/codehaus/mojo/properties/AbstractWritePropertiesMojo.java

@@ -19,11 +19,10 @@
  * under the License.
  */
 
-import java.io.File;
-import java.io.FileNotFoundException;
-import java.io.FileOutputStream;
-import java.io.IOException;
+import java.io.*;
+import java.util.Enumeration;
 import java.util.Properties;
+import java.util.regex.Pattern;
 
 /*
  * Licensed to the Apache Software Foundation (ASF) under one
@@ -63,6 +62,12 @@ public abstract class AbstractWritePropertiesMojo
     @Parameter( required = true )
     private File outputFile;
 
+    @Parameter(required = false)
+    private String exclusionRegex;
+
+    @Parameter(required = false, defaultValue = "true")
+    private boolean generateCommentHeader;
+
     /**
      * @param properties {@link Properties}
      * @param file {@link File}
@@ -71,11 +76,29 @@ public abstract class AbstractWritePropertiesMojo
     protected void writeProperties( Properties properties, File file )
         throws MojoExecutionException
     {
+        // Filter keys and/or the header comment
+        final Properties propertiesToWrite = generateCommentHeader ? new Properties() : new PropertiesWithoutHeader();
+        if (this.exclusionRegex == null) {
+            propertiesToWrite.putAll(properties);
+        } else {
+            final Pattern exclusionPattern = Pattern.compile(exclusionRegex);
+            final Enumeration<?> enumeration = properties.keys();
+            while ( enumeration.hasMoreElements() )
+            {
+                final String key = (String) enumeration.nextElement();
+                if (!exclusionPattern.matcher(key).find()) {
+                    propertiesToWrite.put(key, properties.getProperty(key));
+                }
+            }
+        }
+
+        // Write the properties
         FileOutputStream fos = null;
         try
         {
             fos = new FileOutputStream( file );
-            properties.store( fos, "Properties" );
+            propertiesToWrite.store( fos, "Properties" );
+
         }
         catch ( FileNotFoundException e )
         {
@@ -132,4 +155,18 @@ public File getOutputFile()
         return outputFile;
     }
 
+    /**
+     * @return {@link #exclusionRegex}
+     */
+    public String getExclusionRegex() {
+        return exclusionRegex;
+    }
+
+    /**
+     * @return {@link #generateCommentHeader}
+     */
+    public boolean getGenerateCommentHeader() {
+        return generateCommentHeader;
+    }
+
 }

src/main/java/org/codehaus/mojo/properties/PropertiesWithoutHeader.java

@@ -0,0 +1,59 @@
+package org.codehaus.mojo.properties;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Properties;
+
+/*
+ * 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.
+ */
+
+/**
+ * PropertiesWithoutHeader
+ *
+ * Properties without writing header comment and generated timestamp at the beginning of the properties file
+ *
+ */
+public class PropertiesWithoutHeader extends Properties {
+
+    private static final long serialVersionUID = 8667775349218327383L;
+
+    private static class SkipFirstLineStream extends FilterOutputStream {
+
+        private boolean firstLineDetected = false;
+
+        public SkipFirstLineStream(final OutputStream out) {
+            super(out);
+        }
+
+        @Override
+        public void write(final int b) throws IOException {
+            if (firstLineDetected) {
+                super.write(b);
+            } else if (b == '\n') {
+                firstLineDetected = true;
+            }
+        }
+    }
+
+    @Override
+    public void store(final OutputStream out, final String comments) throws IOException {
+        super.store(new SkipFirstLineStream(out), null);
+    }
+}