INT-3691 Add ZookeeperMetadataStore

JIRA: https://jira.spring.io/browse/INT-3691

- create new core interfaces `ListenableMetadataStore` and `MessageStoreListener`;
- create new module `spring-integration-zookeeper`;
- add `ZookeeperMetadataStore` implementation

Polishing

Polishing

- moved classes into core/test where necessary, including conversion methods
- properly renamed `MetadataStoreListenerAdapter`

spring-integration-core/src/main/java/org/springframework/integration/metadata/ListenableMetadataStore.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2002-2015 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.integration.metadata;
+
+/**
+ *
+ * {@link ConcurrentMetadataStore} with the ability of registering {@link MetadataStoreListener} callbacks, to be
+ * invoked when changes occur in the metadata store.
+ *
+ * @author Marius Bogoevici
+ */
+public interface ListenableMetadataStore extends ConcurrentMetadataStore {
+
+	/**
+	 * Registers a listener with the metadata store
+	 *
+	 * @param callback the callback to be registered
+	 */
+	void addListener(MetadataStoreListener callback);
+
+	/**
+	 * Unregisters a listener
+	 *
+	 * @param callback the callback to be unregistered
+	 */
+	void removeListener(MetadataStoreListener callback);
+}

spring-integration-core/src/main/java/org/springframework/integration/metadata/MetadataStoreListener.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2015 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.integration.metadata;
+
+/**
+ * A callback to be invoked whenever a value changes in the data store.
+ *
+ * @author Marius Bogoevici
+ */
+public interface MetadataStoreListener {
+
+	/**
+	 * Invoked when a key is added to the store
+	 *
+	 * @param key the key being added
+	 * @param value the value being added
+	 */
+	void onAdd(String key, String value);
+
+	/**
+	 * Invoked when a key is removed from the store
+	 *
+	 * @param key the key being removed
+	 * @param oldValue the value being removed
+	 */
+	void onRemove(String key, String oldValue);
+
+	/**
+	 * Invoked when a key is updated into the store
+	 * @param key the key being updated
+	 * @param newValue the new value
+	 */
+	void onUpdate(String key, String newValue);
+}

spring-integration-core/src/main/java/org/springframework/integration/metadata/MetadataStoreListenerAdapter.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2015 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.integration.metadata;
+
+/**
+ * Base implementation for a {@link MetadataStoreListener}. Subclasses may override any of the methods.
+ *
+ * @author Marius Bogoevici
+ */
+public abstract class MetadataStoreListenerAdapter implements MetadataStoreListener {
+
+	@Override
+	public void onAdd(String key, String value) {
+
+	}
+
+	@Override
+	public void onRemove(String key, String oldValue) {
+
+	}
+
+	@Override
+	public void onUpdate(String key, String newValue) {
+
+	}
+}

spring-integration-core/src/main/java/org/springframework/integration/support/utils/IntegrationUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 the original author or authors.
+ * Copyright 2014-2015 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.
@@ -15,6 +15,8 @@
  */
 package org.springframework.integration.support.utils;
 
+import java.io.UnsupportedEncodingException;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
@@ -23,11 +25,13 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.integration.support.DefaultMessageBuilderFactory;
 import org.springframework.integration.support.MessageBuilderFactory;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 /**
  * General utility methods.
  *
  * @author Gary Russell
+ * @author Marius Bogoevici
  * @since 4.0
  *
  */
@@ -98,4 +102,37 @@ public class IntegrationUtils {
 		return beanFactory.getBean(beanName, type);
 	}
 
+	/**
+	 * Utility method for null-safe conversion from String to byte[]
+	 *
+	 * @param value the String to be converted
+	 * @param encoding the encoding
+	 * @return the byte[] corresponding to the given String and encoding, null if provided String argument was null
+	 * @throws IllegalArgumentException if the encoding is not supported
+	 */
+	public static byte[] stringToBytes(String value, String encoding) {
+		try {
+			return value != null ? value.getBytes(encoding) : null;
+		}
+		catch (UnsupportedEncodingException e) {
+			throw new IllegalArgumentException(e);
+		}
+	}
+
+	/**
+	 * Utility method for null-safe conversion from byte[] to String
+	 *
+	 * @param bytes the byte[] to be converted
+	 * @param encoding the encoding
+	 * @return the String corresponding to the given byte[] and encoding, null if provided byte[] argument was null
+	 * @throws IllegalArgumentException if the encoding is not supported
+	 */
+	public static String bytesToString(byte[] bytes, String encoding) {
+		try {
+			return bytes == null ? null : new String(bytes, encoding);
+		}
+		catch (UnsupportedEncodingException e) {
+			throw new IllegalArgumentException(e);
+		}
+	}
 }