Failed to copy artifact or file with maven packaging a web application

I had the same error message before. In pom.xml I changed maven-war-plugin version from 2.3 to 2.6, then the project was built successfully.

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-war-plugin</artifactId>
    <version>2.6</version>
</plugin>

This has nothing to do with security: under Windows, this problem occurs when a process doesn't "close" correctly its usage of a folder. We got the problem with apt-maven-plugin: in a complex multi-modules project, when a module using this plug-in, is then later referenced in an über jar building pom, then we got this error during the build of the über jar on the target/classes folder of the module using apt-maven-plugin. When resuming the build (mvn params -rf :offending_module), the problem disappears because the Maven process launching the apt-maven-plugin is dead, thus the lock of the folder is released.

Very annoying to say the least.