maven-resources-plugin error using copy-resources goal: 'resources', 'outputDirectory' missing or invalid

Question

I'm trying to use the maven-resources-plugin to do some filtering using the copy-resources goal, and ran into the following error:

Failed to execute goal org.apache.maven.plugins:maven-resources-plugin:2.5:copy-resources (default-cli) on project bar: The parameters 'resources', 'outputDirectory' for goal org.apache.maven.plugins:maven-resources-plugin:2.5:copy-resources are missing or invalid

To isolate the problem, I created a very simple pom.xml, copied pretty nearly verbatim from http://maven.apache.org/plugins/maven-resources-plugin/examples/copy-resources.html, ran it, and got the same error.

I'm invoking it with

mvn resources:copy-resources

Any ideas? Here's the test pom.xml.

<?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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>foo</groupId>
  <artifactId>bar</artifactId>
  <version>1.0-SNAPSHOT</version>
  <build>
    <plugins>
      <plugin>
        <artifactId>maven-resources-plugin</artifactId>
        <version>2.5</version>
        <executions>
          <execution>
            <id>copy-resources</id>
            <!-- here the phase you need -->
            <phase>validate</phase>
            <goals>
              <goal>copy-resources</goal>
            </goals>
            <configuration>
              <outputDirectory>${basedir}/target/extra-resources</outputDirectory>
              <resources>          
                <resource>
                  <directory>src/non-packaged-resources</directory>
                  <filtering>true</filtering>
                </resource>
              </resources>              
            </configuration>            
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

Answer 1

The main problem you had is that you are invoking the plugin goal directly using

mvn resources:copy-resources

which does not necessarily create the output directory. Instead call the correct Maven lifecycle phase.

mvn process-resources

For a complete list of the lifecycle phases just run the mvn command without anything..

In general it almost always better to invoke a lifecycle phase rather than a goal directly since it guarantees that any preconditions are met (e.g. cant compile test classes before the classes to be tested..).