public void run()

in core/src/main/java/org/apache/sling/cms/core/internal/operations/MembershipOperation.java [50:103]
45 lines of code
8 McCabe index (conditional complexity)

    public void run(SlingHttpServletRequest request, PostResponse response, SlingPostProcessor[] processors) {
        final List<Modification> changes = new ArrayList<>();
        try {

            List<String> groups = new ArrayList<>();
            Optional.ofNullable(request.getParameterValues(PN_MEMBERSHIP))
                    .ifPresent(p -> groups.addAll(Arrays.asList(p)));

            AuthorizableWrapper authWrapper = request.getResource().adaptTo(AuthorizableWrapper.class);

            Authorizable auth = authWrapper.getAuthorizable();
            response.setPath(auth.getPath());
            changes.add(Modification.onModified(auth.getPath()));

            auth.declaredMemberOf().forEachRemaining(group -> {
                try {
                    if (!groups.contains(group.getPath())) {
                        log.debug("Removing member {} from {}", auth, group);
                        group.removeMember(auth);
                        changes.add(Modification.onModified(group.getPath()));
                    } else {
                        groups.remove(group.getPath());
                    }
                } catch (RepositoryException e) {
                    log.warn("Failed to remove members", e);
                }
            });

            for (String path : groups) {
                Resource resource = request.getResourceResolver().getResource(path);
                if (resource == null) {
                    throw new RepositoryException("Failed to resolve authorizable at " + path);
                }
                Group group = (Group) resource.adaptTo(AuthorizableWrapper.class).getAuthorizable();
                group.addMember(auth);
                changes.add(Modification.onModified(group.getPath()));
                log.debug("Adding member {} to {}", auth, group);
            }

            // invoke processors
            if (processors != null) {
                for (SlingPostProcessor processor : processors) {
                    processor.process(request, changes);
                }
            }

            request.getResourceResolver().commit();

            response.onModified(auth.getPath());
        } catch (Exception e) {
            log.warn("Failed to update membership", e);
            response.setError(e);
        }
    }