private PageClassLoaderContext merge()

in tapestry-core/src/main/java/org/apache/tapestry5/services/pageload/PageClassLoaderContextManagerImpl.java [342:453]
82 lines of code
12 McCabe index (conditional complexity)

    private PageClassLoaderContext merge(
            Set<PageClassLoaderContext> contextDependencies,
            Function<ClassLoader, PlasticProxyFactory> plasticProxyFactoryProvider,
            PageClassLoaderContext root, Set<String> classesToInvalidate) 
    {
        
        NESTED_MERGE_COUNT.set(NESTED_MERGE_COUNT.get() + 1);
        
        if (LOGGER.isDebugEnabled())
        {
            
            LOGGER.debug("Nested merge count going up to {}", NESTED_MERGE_COUNT.get());

            String classes;
            StringBuilder builder = new StringBuilder();
            builder.append("Merging the following page classloader contexts into one:\n");
            for (PageClassLoaderContext context : contextDependencies) 
            {
                classes = context.getClassNames().stream()
                        .map(this::getContextName)
                        .sorted()
                        .collect(Collectors.joining(", "));
                builder.append(String.format("\t%s (parent %s) (%s)\n", context.getName(), context.getParent().getName(), classes));
            }
            LOGGER.debug(builder.toString().trim());
        }
        
        Set<PageClassLoaderContext> allContextsIncludingDescendents = new HashSet<>();
        for (PageClassLoaderContext context : contextDependencies) 
        {
            allContextsIncludingDescendents.add(context);
            allContextsIncludingDescendents.addAll(context.getDescendents());
        }

        PageClassLoaderContext merged;
        
        // Collect the classes in these dependencies, then invalidate the contexts
        
        Set<PageClassLoaderContext> furtherDependencies = new HashSet<>();
        
        Set<String> classNames = new HashSet<>();
        
        for (PageClassLoaderContext context : contextDependencies) 
        {
            if (!context.isRoot())
            {
                classNames.addAll(context.getClassNames());
            }
            final PageClassLoaderContext parent = context.getParent();
            // We don't want the merged context to have a further dependency on 
            // the root context (it's not mergeable) nor on itself.
            if (!parent.isRoot() && 
                    !allContextsIncludingDescendents.contains(parent))
            {
                furtherDependencies.add(parent);
            }
        }
        
        final List<PageClassLoaderContext> contextsToInvalidate = contextDependencies.stream()
            .filter(c -> !c.isRoot())
            .collect(Collectors.toList());
        
        if (!contextsToInvalidate.isEmpty())
        {
            classesToInvalidate.addAll(invalidate(contextsToInvalidate.toArray(new PageClassLoaderContext[contextsToInvalidate.size()])));
        }
        
        PageClassLoaderContext parent;
        
        // No context dependencies, so parent is going to be the root one
        if (furtherDependencies.size() == 0)
        {
            parent = root;
        }
        else 
        {
            // Single shared context dependency, so it's our parent
            if (furtherDependencies.size() == 1)
            {
                parent = furtherDependencies.iterator().next();
            }
            // No single context dependency, so we'll need to recursively merge it
            // so we can have a single parent.
            else
            {
                parent = merge(furtherDependencies, plasticProxyFactoryProvider, root, classesToInvalidate);
                LOGGER.debug("New context: {}", parent);
            }
        }
        
        merged = new PageClassLoaderContext(
            "merged " + MERGED_COUNTER.getAndIncrement(),
            parent, 
            classNames, 
            plasticProxyFactoryProvider.apply(parent.getClassLoader()),
            this::get);
        
        parent.addChild(merged);
        
//        for (String className : classNames) 
//        {
//            loadClass(className, merged);
//        }
        
        NESTED_MERGE_COUNT.set(NESTED_MERGE_COUNT.get() - 1);
        if (LOGGER.isDebugEnabled())
        {
            LOGGER.debug("Nested merge count going down to {}", NESTED_MERGE_COUNT.get());
        }
        
        return merged;
    }