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-test/src/main/java/org/springframework/integration/test/matcher/EqualsResultMatcher.java

@@ -0,0 +1,57 @@
+/*
+ * 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.test.matcher;
+
+import org.hamcrest.Description;
+import org.hamcrest.DiagnosingMatcher;
+
+import org.springframework.util.ObjectUtils;
+
+/**
+ * A matcher that evaluates against the result of invoking a function,
+ * wrapped by the {@link EqualsResultMatcher.Evaluator}
+ *
+ * The goal is to defer the computation until the matcher needs to be actually evaluated.
+ * Mainly useful in conjunction with retrying matcherss such as {@link EventuallyMatcher}
+ *
+ * @author Marius Bogoevici
+ */
+public class EqualsResultMatcher<U> extends DiagnosingMatcher<U> {
+
+	private Evaluator<U> evaluator;
+
+	public EqualsResultMatcher(Evaluator<U> evaluator) {
+		this.evaluator = evaluator;
+	}
+
+	@Override
+	protected boolean matches(Object item, Description mismatchDescription) {
+		return ObjectUtils.nullSafeEquals(item, evaluator.evaluate());
+	}
+
+	@Override
+	public void describeTo(Description description) {
+	}
+
+	public interface Evaluator<U> {
+		U evaluate();
+	}
+
+	public static <U> EqualsResultMatcher<U> equalsResult(Evaluator<U> evaluator) {
+		return new EqualsResultMatcher<U>(evaluator);
+	}
+}

spring-integration-test/src/main/java/org/springframework/integration/test/matcher/EventuallyMatcher.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2013-2104 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.test.matcher;
+
+import org.hamcrest.Description;
+import org.hamcrest.DiagnosingMatcher;
+import org.hamcrest.Matcher;
+
+
+/**
+ * A matcher that will evaluate another matcher repeatedly until it matches, or fail after some number of attempts.
+ *
+ * @param <U> the type the wrapped matcher operates on
+ *
+ * (Copied from {@code org.springframework.xd.test.fixtures.EventuallyMatcher})
+ *
+ * @author Eric Bottard
+ */
+public class EventuallyMatcher<U> extends DiagnosingMatcher<U> {
+
+	private final Matcher<U> delegate;
+
+	private int nbAttempts;
+
+	private int pause;
+
+	public EventuallyMatcher(Matcher<U> delegate) {
+		this(delegate, 20, 100);
+	}
+
+	public EventuallyMatcher(Matcher<U> delegate, int nbAttempts, int pause) {
+		this.delegate = delegate;
+		this.nbAttempts = nbAttempts;
+		this.pause = pause;
+	}
+
+	public static <U> Matcher<U> eventually(int nbAttempts, int pause, Matcher<U> delegate) {
+		return new EventuallyMatcher<U>(delegate,nbAttempts,pause);
+	}
+
+	public static <U> Matcher<U> eventually(Matcher<U> delegate) {
+		return new EventuallyMatcher<U>(delegate);
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		description.appendDescriptionOf(delegate).appendText(String.format(", trying at most %d times", nbAttempts));
+	}
+
+	@Override
+	protected boolean matches(Object item, Description mismatchDescription) {
+		mismatchDescription.appendText(String.format("failed after %d*%d=%dms:%n", nbAttempts, pause, nbAttempts
+				* pause));
+		for (int i = 0; i < nbAttempts; i++) {
+			boolean result = delegate.matches(item);
+			if (result) {
+				return true;
+			}
+			delegate.describeMismatch(item, mismatchDescription);
+			mismatchDescription.appendText(", ");
+			try {
+				Thread.sleep(pause);
+			}
+			catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+				break;
+			}
+		}
+		return false;
+	}
+}