RuntimeClasspathCaplet.java

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.nio.file.Paths;

/** Caplet to include runtime classpath. */
public class RuntimeClasspathCaplet extends Capsule {
    private static final String PROP_RUNTIME_CP = "caplet.runtime.classpath";

    /** Composition constructor. */
    public RuntimeClasspathCaplet(final Capsule prev) {
        super(prev);
    }

    // Regrettably we can't use any external libraries in this method (e.g.
    // Guava) that are not used by the core Capsule jar because this method is
    // invoked prior to the capsule being expanded.
    @Override
    @SuppressWarnings("unchecked")
    protected <T> T attribute(Map.Entry<String, T> attr) {
        if (attr != ATTR_APP_CLASS_PATH) {
            return super.attribute(attr);
        }
        String classpath = System.getProperty(PROP_RUNTIME_CP);
        if (classpath == null || classpath.isEmpty()) {
            return super.attribute(attr);
        }
        List<Object> cplist = new ArrayList<>(
                (List<Object>) super.attribute(attr));
        for (String component : classpath.split(":")) {
            cplist.add(Paths.get(component).toAbsolutePath().normalize()
                    .toString());
        }
        return (T) cplist;
    }
}