ZooKeeperUtils.java

/*
 * Copyright 2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.xd.dirt.zookeeper;


import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.Collections;
import java.util.EnumSet;
import java.util.Map;

import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.slf4j.Logger;

import org.springframework.core.convert.converter.Converter;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
import com.fasterxml.jackson.databind.ObjectWriter;

/**
 * Utility methods for ZooKeeper.
 *
 * @author David Turanski
 * @author Patrick Peralta
 * @author Ilayaperumal Gopinathan
 */
public abstract class ZooKeeperUtils {

	/**
	 * Utility to convert byte arrays to maps of strings.
	 */
	private static final MapBytesUtility mapBytesUtility = new MapBytesUtility();

	/**
	 * {@link Converter} from {@link ChildData} to the leaf path name string.
	 */
	public static final StripPathConverter stripPathConverter = new StripPathConverter();

	/**
	 * Converter from {@link ChildData} to leaf name string.
	 */
	public static class StripPathConverter implements Converter<ChildData, String> {

		/**
		 * {@inheritDoc}
		 */
		@Override
		public String convert(ChildData source) {
			return Paths.stripPath(source.getPath());
		}
	}

	/**
	 * Convert a map of string key/value pairs to a JSON string in a byte array.
	 *
	 * @param map map to convert
	 *
	 * @return byte array
	 */
	public static byte[] mapToBytes(Map<String, String> map) {
		return mapBytesUtility.toByteArray(map);
	}

	/**
	 * Convert a byte array containing a JSON string to a map of key/value pairs.
	 *
	 * @param bytes byte array containing the key/value pair strings
	 *
	 * @return a new map instance containing the key/value pairs
	 */
	public static Map<String, String> bytesToMap(byte[] bytes) {
		return mapBytesUtility.toMap(bytes);
	}

	/**
	 * Utility method to wrap a Throwable in a {@link ZooKeeperAccessException}.
	 * @param t the throwable
	 */
	public static RuntimeException wrapThrowable(Throwable t) {
		return wrapThrowable(t, null);
	}

	/**
	 * Utility method to wrap a Throwable in a {@link ZooKeeperAccessException}.
	 * @param t the throwable
	 * @param message use this message if not null
	 */
	public static RuntimeException wrapThrowable(Throwable t, String message) {
		if (message != null) {
			return new ZooKeeperAccessException(message, t);
		}
		if (t instanceof RuntimeException) {
			return (RuntimeException) t;
		}
		else {
			return new ZooKeeperAccessException(t.getMessage(), t);
		}
	}

	/**
	 * Throw a wrapped exception ignoring specific Exception types, if any.
	 * @param t the throwable
	 * @param ignored a varargs list of ignored exception types
	 */
	@SuppressWarnings({"unchecked", "rawtypes"})
	public static void wrapAndThrowIgnoring(Throwable t, Class... ignored) {
		if (ignored != null) {
			for (Class<? extends Exception> e : ignored) {
				if (e.isAssignableFrom(t.getClass())) {
					return;
				}
			}
		}
		throw wrapThrowable(t);
	}

	/**
	 * Utility method to log {@link org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent events}.
	 *
	 * @param logger logger to write to
	 * @param event  event to log
	 */
	public static void logCacheEvent(Logger logger, PathChildrenCacheEvent event) {
		ChildData data = event.getData();
		StringBuilder builder = new StringBuilder();
		builder.append("Path cache event: ");
		if (data != null && data.getPath() != null) {
			builder.append("path=").append(data.getPath()).append(", ");
		}
		builder.append("type=").append(event.getType());

		if (EnumSet.of(PathChildrenCacheEvent.Type.CONNECTION_SUSPENDED,
				PathChildrenCacheEvent.Type.CONNECTION_LOST).contains(event.getType())) {
			logger.warn(builder.toString());
		}
		else {
			logger.info(builder.toString());
		}

		if (data != null && logger.isTraceEnabled()) {
			String content;
			byte[] bytes = data.getData();
			if (bytes == null || bytes.length == 0) {
				content = "empty";
			}
			else {
				try {
					content = new String(data.getData(), "UTF-8");
				}
				catch (UnsupportedEncodingException e) {
					content = "Could not convert content to UTF-8: " + e.toString();
				}
			}
			logger.trace("Data for path {}: {}", data.getPath(), content);
		}
	}

	/**
	 * Return the full stack trace for a Throwable.
	 *
	 * @param t throwable for which to obtain the full stack trace
	 * @return string containing the full stack trace
	 */
	public static String getStackTrace(Throwable t) {
		StringWriter stringWriter = new StringWriter();
		PrintWriter printWriter = new PrintWriter(stringWriter);
		t.printStackTrace(printWriter);

		return stringWriter.toString();
	}


	/**
	 * Utility to convert {@link Map string key/value pairs} to/from byte arrays containing JSON strings. By default the
	 * JSON library encodes to UTF-8.
	 *
	 * @author Patrick Peralta
	 */
	private static class MapBytesUtility {

		/**
		 * Serializer from map to JSON string in a byte array.
		 */
		private final ObjectWriter writer;

		/**
		 * Deserializer from JSON string in a byte array to a map.
		 */
		private final ObjectReader reader;

		/**
		 * Construct a MapBytesUtility.
		 */
		private MapBytesUtility() {
			ObjectMapper mapper = new ObjectMapper();
			writer = mapper.writer();
			reader = mapper.reader(Map.class);
		}

		/**
		 * Convert a map of string key/value pairs to a JSON string in a byte array.
		 *
		 * @param map map to convert
		 *
		 * @return byte array
		 */
		private byte[] toByteArray(Map<String, String> map) {
			try {
				return writer.writeValueAsBytes(map);
			}
			catch (JsonProcessingException e) {
				throw new RuntimeException(e);
			}
		}

		/**
		 * Convert a byte array containing a JSON string to a map of key/value pairs.
		 *
		 * @param bytes byte array containing the key/value pair strings
		 *
		 * @return a new map instance containing the key/value pairs
		 */
		private Map<String, String> toMap(byte[] bytes) {
			if (bytes == null || bytes.length == 0) {
				return Collections.emptyMap();
			}
			try {
				return reader.readValue(bytes);
			}
			catch (Exception e) {
				String contents;
				try {
					contents = new String(bytes, "UTF-8");
				}
				catch (UnsupportedEncodingException uue) {
					contents = "Could not read content due to " + uue;
				}
				throw new RuntimeException("Error parsing JSON string: " + contents, e);
			}
		}
	}

}