Conditional delegation in a ClassLoader

ConditionalDelegationClassLoader.java

public class ConditionalDelegationClassLoader extends URLClassLoader
{
    private final String parentPrefix;
    private final String childPrefix;

    public ConditionalDelegationClassLoader(URL[] urls, String parentPrefix, String childPrefix)
    {
        super(urls);

        this.parentPrefix = parentPrefix;
        this.childPrefix = childPrefix;
    }

    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException
    {
        Class<?> c = findLoadedClass(name);

        if (c == null)
        {
            boolean parentFirst = (parentPrefix == null || name.startsWith(parentPrefix)) && // load from parent
                                  (childPrefix == null || !name.startsWith(childPrefix));    // don't load from child

            if (parentFirst)
            {
                try
                {
                    c = super.loadClass(name);
                }
                catch (ClassNotFoundException e)
                {
                }
            }

            if (c == null)
            {
                try
                {
                    c = findClass(name);
                }
                catch (ClassNotFoundException e)
                {
                    if (parentFirst)
                    {
                        throw e; // we didn't find it in the parent or the child
                    }
                    else
                    {
                        c = super.loadClass(name); // load from the parent now
                    }
                }
            }
        }

        return c;
    }
}