spring3.1: factory bean that allows to map url-path -> handler-interceptors

HandlerInterceptorsFactory

/**
 * Factory bean to generate list of HandlerMappings and MappedHandlers.
 *
 * MappedHandlers can be specified by url path to interceptors.
 *
 */
public class HandlerInterceptorsFactory extends AbstractFactoryBean<List<Object>> {

	private List<HandlerInterceptor> handlerInterceptors = new ArrayList<HandlerInterceptor>();

	private Map<String, List<HandlerInterceptor>> interceptorsByPath =
			new LinkedHashMap<String, List<HandlerInterceptor>>();

	private List<MappedInterceptor> additionalMappedInterceptors = new ArrayList<MappedInterceptor>();

	@Override
	public Class<?> getObjectType() {
		return List.class;
	}

	public HandlerInterceptorsFactory() {
		super();
	}

	@Override
	protected List<Object> createInstance() throws Exception {

		final List<MappedInterceptor> mappedInterceptors = getMappedInterceptors();

		final List<Object> interceptors = new ArrayList<Object>();
		interceptors.addAll(mappedInterceptors);
		interceptors.addAll(additionalMappedInterceptors);
		interceptors.addAll(handlerInterceptors); // regular interceptors
		return interceptors;

	}

	private List<MappedInterceptor> getMappedInterceptors() {

		// convert (path -> interceptors) to (interceptor -> paths)
		final Map<HandlerInterceptor, List<String>> map = new LinkedHashMap<HandlerInterceptor, List<String>>();
		for (Map.Entry<String, List<HandlerInterceptor>> entry : interceptorsByPath.entrySet()) {
			final String path = entry.getKey();
			final List<HandlerInterceptor> interceptors = entry.getValue();

			for (HandlerInterceptor interceptor : interceptors) {

				List<String> paths = map.get(interceptor);
				if (paths == null) {
					paths = new ArrayList<String>();
					map.put(interceptor, paths);
				}

				paths.add(path);
			}
		}

		final List<MappedInterceptor> result = new ArrayList<MappedInterceptor>();

		// create mapped interceptors
		for (Map.Entry<HandlerInterceptor, List<String>> entry : map.entrySet()) {
			final HandlerInterceptor interceptor = entry.getKey();
			final List<String> paths = entry.getValue();

			final MappedInterceptor mappedInterceptor =
					new MappedInterceptor(paths.toArray(new String[paths.size()]), interceptor);

			result.add(mappedInterceptor);
		}

		return result;

	}

	public void setInterceptorsByPath(Map<String, List<HandlerInterceptor>> interceptorsByPath) {
		this.interceptorsByPath = interceptorsByPath;
	}

	public void setHandlerInterceptors(List<HandlerInterceptor> handlerInterceptors) {
		this.handlerInterceptors = handlerInterceptors;
	}

	public void setAdditionalMappedInterceptors(List<MappedInterceptor> additionalMappedInterceptors) {
		this.additionalMappedInterceptors = additionalMappedInterceptors;
	}
}