Add outputEncoding parameter to enable encoding conversion (MRESOURCES-232)

pom.xml

@@ -76,7 +76,7 @@ under the License.
     <javaVersion>17</javaVersion>
 
     <guiceVersion>7.0.0</guiceVersion>
-    <mavenFilteringVersion>4.0.0-beta-1</mavenFilteringVersion>
+    <mavenFilteringVersion>4.0.0-beta-2-SNAPSHOT</mavenFilteringVersion>
     <mavenPluginPluginVersion>4.0.0-beta-2</mavenPluginPluginVersion>
     <mavenPluginTestingVersion>4.0.0-beta-4</mavenPluginTestingVersion>
     <plexusBuildApiVersion>0.0.7</plexusBuildApiVersion>

src/it/MRESOURCES-232/pom.xml

@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+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.
+-->
+<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/maven-v4_0_0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>org.apache.maven.plugins.maven-resources-plugin.its</groupId>
+  <artifactId>MRESOURCES-232</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+  <name>MRESOURCES-232: separate input and output encoding for resource filtering</name>
+
+  <properties>
+    <world>World</world>
+  </properties>
+
+  <build>
+    <resources>
+      <resource>
+        <filtering>true</filtering>
+        <directory>src/main/resources</directory>
+      </resource>
+    </resources>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-resources-plugin</artifactId>
+        <version>@project.version@</version>
+        <configuration>
+          <!-- Read resources as ISO-8859-1, write as UTF-8 -->
+          <encoding>ISO-8859-1</encoding>
+          <outputEncoding>UTF-8</outputEncoding>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>

src/it/MRESOURCES-232/src/main/resources/message.txt

@@ -0,0 +1 @@
+Bonjour ${world}! café

src/it/MRESOURCES-232/verify.groovy

@@ -0,0 +1,38 @@
+/*
+ * 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.
+ */
+// MRESOURCES-232: Verify that outputEncoding enables encoding conversion during filtering.
+// The source file (message.txt) is ISO-8859-1-encoded and contains a filter token and an
+// é character (0xE9 in Latin-1). After filtering with encoding=ISO-8859-1 and
+// outputEncoding=UTF-8 the output file must:
+//   1. Have the token expanded (${world} → World)
+//   2. Encode é as UTF-8 (0xC3 0xA9)
+
+File output = new File( basedir, 'target/classes/message.txt' );
+assert output.exists() : "message.txt was not copied";
+
+// Read as UTF-8 — if the file were still Latin-1 this would produce garbage for é
+String content = output.getText( 'UTF-8' );
+assert content.trim() == 'Bonjour World! caf\u00e9' : "Unexpected content: '${content.trim()}'"
+
+// Also verify the raw bytes: é should be the two-byte UTF-8 sequence 0xC3 0xA9
+byte[] bytes = output.bytes;
+String hex = bytes.collect { String.format('%02x', it & 0xFF) }.join(' ');
+assert hex.contains('c3 a9') : "Expected UTF-8 é (c3 a9) in output bytes, got: ${hex}"
+
+return true;

src/main/java/org/apache/maven/plugins/resources/ResourcesMojo.java

@@ -61,6 +61,26 @@ public class ResourcesMojo implements org.apache.maven.api.plugin.Mojo {
     @Parameter(defaultValue = "${project.build.sourceEncoding}")
     protected String encoding;
 
+    /**
+     * The character encoding to use when writing filtered resources.
+     * When set, enables encoding conversion during filtering: resources are read with {@link #encoding}
+     * and written with this encoding. Useful to convert legacy EBCDIC or Latin-1 source files to UTF-8
+     * (or vice-versa) as part of the build.
+     * <p>
+     * When not set (the default), the same encoding is used for reading and writing, preserving
+     * backward compatibility.
+     * </p>
+     * <p>
+     * This parameter is ignored when filtering is disabled (i.e. when no resource has
+     * {@code &lt;filtering&gt;true&lt;/filtering&gt;}), because non-filtered files are always copied
+     * as raw bytes.
+     * </p>
+     *
+     * @since 3.4.1
+     */
+    @Parameter(property = "maven.resources.outputEncoding")
+    protected String outputEncoding;
+
     /**
      * The character encoding to use when reading and writing filtered properties files.
      * If not specified, it will default to the value of the "encoding" parameter.
@@ -357,6 +377,11 @@ protected void doExecute() throws MojoException {
             // Handle MRESOURCES-171
             mavenResourcesExecution.setPropertiesEncoding(propertiesEncoding);
 
+            // Handle MRESOURCES-232: separate input/output encoding for encoding conversion
+            if (outputEncoding != null) {
+                mavenResourcesExecution.setOutputEncoding(outputEncoding);
+            }
+
             if (nonFilteredFileExtensions != null) {
                 mavenResourcesExecution.setNonFilteredFileExtensions(nonFilteredFileExtensions);
             }