INT-3907: Downgrade to Kryo-2.22

JIRA: https://jira.spring.io/browse/INT-3907

The IO-1.1.x is based on the Kryo-2.22 and can't be upgraded to 3.0.
Therefore we should downgrade.

* Change `PojoCodec` to use `StdInstantiatorStrategy` directly, because the `DefaultInstantiatorStrategy` logic is as a core code of `Kryo`.
* Introduce `org.springframework.integration.codec.kryo.pool` package and copy/paste `com.esotericsoftware.kryo.pool` classes,
 since they have been introduced since Kryo-3.0.
* That copy/paste seemed to me the simplest fix, since the `KryoPool` logic is encapsulated in the `AbstractKryoCodec`

build.gradle

@@ -106,7 +106,7 @@ subprojects { subproject ->
 		jsonpathVersion = '0.9.1'
 		junitVersion = '4.11'
 		jythonVersion = '2.5.3'
-		kryoShadedVersion = '3.0.3'
+		kryoVersion = '2.22'
 		log4jVersion = '1.2.17'
 		mockitoVersion = '1.9.5'
 		mysqlVersion = '5.1.29'
@@ -268,7 +268,7 @@ project('spring-integration-core') {
 		compile("com.fasterxml.jackson.core:jackson-databind:$jackson2Version", optional)
 		compile("com.jayway.jsonpath:json-path:$jsonpathVersion", optional)
 		compile("io.fastjson:boon:$boonVersion", optional)
-		compile("com.esotericsoftware:kryo-shaded:$kryoShadedVersion", optional)
+		compile("com.esotericsoftware.kryo:kryo:$kryoVersion", optional)
 
 		testCompile ("org.aspectj:aspectjweaver:$aspectjVersion")
 		testCompile ("net.openhft:chronicle:$chronicleVersion")

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/AbstractKryoCodec.java

@@ -22,14 +22,14 @@ import java.io.InputStream;
 import java.io.OutputStream;
 
 import org.springframework.integration.codec.Codec;
+import org.springframework.integration.codec.kryo.pool.KryoCallback;
+import org.springframework.integration.codec.kryo.pool.KryoFactory;
+import org.springframework.integration.codec.kryo.pool.KryoPool;
 import org.springframework.util.Assert;
 
 import com.esotericsoftware.kryo.Kryo;
 import com.esotericsoftware.kryo.io.Input;
 import com.esotericsoftware.kryo.io.Output;
-import com.esotericsoftware.kryo.pool.KryoCallback;
-import com.esotericsoftware.kryo.pool.KryoFactory;
-import com.esotericsoftware.kryo.pool.KryoPool;
 
 /**
  * Base class for {@link Codec}s using {@link Kryo}.

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/PojoCodec.java

@@ -19,13 +19,12 @@ package org.springframework.integration.codec.kryo;
 import java.util.Collections;
 import java.util.List;
 
-import org.objenesis.strategy.StdInstantiatorStrategy;
-
 import org.springframework.util.CollectionUtils;
 
 import com.esotericsoftware.kryo.Kryo;
 import com.esotericsoftware.kryo.io.Input;
 import com.esotericsoftware.kryo.io.Output;
+import com.esotericsoftware.shaded.org.objenesis.strategy.StdInstantiatorStrategy;
 
 /**
  * Kryo Codec that can encode and decode arbitrary types. Classes and associated
@@ -99,7 +98,7 @@ public class PojoCodec extends AbstractKryoCodec {
 
 	@Override
 	protected void configureKryoInstance(Kryo kryo) {
-		kryo.setInstantiatorStrategy(new Kryo.DefaultInstantiatorStrategy(new StdInstantiatorStrategy()));
+		kryo.setInstantiatorStrategy(new StdInstantiatorStrategy());
 		if (this.kryoRegistrar != null) {
 			this.kryoRegistrar.registerTypes(kryo);
 		}

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/pool/KryoCallback.java

@@ -0,0 +1,34 @@
+/*
+ * 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.codec.kryo.pool;
+
+import com.esotericsoftware.kryo.Kryo;
+
+/**
+ * Callback to run with a provided kryo instance.
+ * <p>
+ * Copied from Kryo 3.0 to facilitate dropping back to 2.22 for Spring IO
+ * compatibility.
+ *
+ * @author Martin Grotzke
+ *
+ * @param <T> The type of the result of the interaction with kryo.
+ */
+public interface KryoCallback<T> {
+
+	T execute(Kryo kryo);
+
+}

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/pool/KryoFactory.java

@@ -0,0 +1,32 @@
+/*
+ * 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.codec.kryo.pool;
+
+import com.esotericsoftware.kryo.Kryo;
+
+/**
+ * Factory to create new configured instances of {@link Kryo}.
+ * <p>
+ * Copied from Kryo 3.0 to facilitate dropping back to 2.22 for Spring IO
+ * compatibility.
+ *
+ * @author Martin Grotzke
+ */
+public interface KryoFactory {
+
+	Kryo create();
+
+}

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/pool/KryoPool.java

@@ -0,0 +1,143 @@
+/*
+ * 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.codec.kryo.pool;
+
+import java.lang.ref.SoftReference;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+import com.esotericsoftware.kryo.Kryo;
+
+/**
+ * A simple pool interface for {@link Kryo} instances. Use the {@link KryoPool.Builder} to
+ * construct a pool instance.
+ * <p>
+ * Copied from Kryo 3.0 to facilitate dropping back to 2.22 for Spring IO
+ * compatibility.
+ * <p>
+ * Usage:
+ * <pre class="code">
+ * {@code
+ *
+ * KryoFactory factory = new KryoFactory() {
+ *   public Kryo create () {
+ *     Kryo kryo = new Kryo();
+ *     // configure kryo instance, customize settings
+ *     return kryo;
+ *   }
+ * };
+ * // Simple pool, you might also activate SoftReferences to fight OOMEs.
+ * KryoPool pool = new KryoPool.Builder(factory).build();
+ * Kryo kryo = pool.borrow();
+ * // do s.th. with kryo here, and afterwards release it
+ * pool.release(kryo);
+ *
+ * // or use a callback to work with kryo (pool.run borrows+releases for you)
+ * String value = pool.run(new KryoCallback<String>() {
+ *   public String execute(Kryo kryo) {
+ *     return kryo.readObject(input, String.class);
+ *   }
+ * });
+ *
+ * }
+ * </pre>
+ * @author Martin Grotzke
+ */
+public interface KryoPool {
+
+	/**
+	 * Takes a {@link Kryo} instance from the pool or creates a new one
+	 * (using the factory) if the pool is empty.
+	 * @return the {@link Kryo} instance.
+	 */
+	Kryo borrow();
+
+	/**
+	 * Returns the given {@link Kryo} instance to the pool.
+	 * @param kryo the {@link Kryo} instance to release.
+	 */
+	void release(Kryo kryo);
+
+	/**
+	 * Runs the provided {@link KryoCallback} with a {@link Kryo} instance
+	 * from the pool (borrow/release around {@link KryoCallback#execute(Kryo)}).
+	 * @param callback the {@link KryoCallback} to call.
+	 * @param <T> The type of the result of the interaction with kryo.
+	 * @return the result of the interaction with {@link Kryo}.
+	 */
+	<T> T run(KryoCallback<T> callback);
+
+	/**
+	 * Builder for a {@link KryoPool} instance, constructs a {@link KryoPoolQueueImpl} instance.
+	 */
+	class Builder {
+
+		private final KryoFactory factory;
+
+		private Queue<Kryo> queue = new ConcurrentLinkedQueue<Kryo>();
+
+		private boolean softReferences;
+
+		public Builder(KryoFactory factory) {
+			if (factory == null) {
+				throw new IllegalArgumentException("factory must not be null");
+			}
+			this.factory = factory;
+		}
+
+		/**
+		 * Use the given queue for pooling kryo instances (by default a {@link ConcurrentLinkedQueue}
+		 * is used).
+		 * @param queue the queue instance to use.
+		 * @return the Builder instance.
+		 */
+		public Builder queue(Queue<Kryo> queue) {
+			if (queue == null) {
+				throw new IllegalArgumentException("queue must not be null");
+			}
+			this.queue = queue;
+			return this;
+		}
+
+		/**
+		 * Use {@link SoftReference}s for pooled {@link Kryo} instances, so that
+		 * instances may be garbage collected when there's memory demand (by default
+		 * disabled).
+		 * @return the Builder instance.
+		 */
+		public Builder softReferences() {
+			softReferences = true;
+			return this;
+		}
+
+		/**
+		 * Build the pool.
+		 * @return the KryoPool instance.
+		 */
+		public KryoPool build() {
+			Queue<Kryo> q = softReferences ? new SoftReferenceQueue(queue) : queue;
+			return new KryoPoolQueueImpl(factory, q);
+		}
+
+		@Override
+		public String toString() {
+			return getClass().getName() + "[queue.class=" + queue.getClass() +
+					", softReferences=" + softReferences + "]";
+		}
+
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/pool/KryoPoolQueueImpl.java

@@ -0,0 +1,74 @@
+/*
+ * 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.codec.kryo.pool;
+
+import java.util.Queue;
+
+import com.esotericsoftware.kryo.Kryo;
+
+/**
+ * A simple {@link Queue} based {@link KryoPool} implementation, should be built
+ * using the KryoPool.Builder.
+ * <p>
+ * Copied from Kryo 3.0 to facilitate dropping back to 2.22 for Spring IO
+ * compatibility.
+ * @author Martin Grotzke
+ */
+class KryoPoolQueueImpl implements KryoPool {
+
+	private final Queue<Kryo> queue;
+
+	private final KryoFactory factory;
+
+	KryoPoolQueueImpl(KryoFactory factory, Queue<Kryo> queue) {
+		this.factory = factory;
+		this.queue = queue;
+	}
+
+	public int size() {
+		return queue.size();
+	}
+
+	@Override
+	public Kryo borrow() {
+		Kryo res;
+		if ((res = queue.poll()) != null) {
+			return res;
+		}
+		return factory.create();
+	}
+
+	@Override
+	public void release(Kryo kryo) {
+		queue.offer(kryo);
+	}
+
+	@Override
+	public <T> T run(KryoCallback<T> callback) {
+		Kryo kryo = borrow();
+		try {
+			return callback.execute(kryo);
+		}
+		finally {
+			release(kryo);
+		}
+	}
+
+	public void clear() {
+		queue.clear();
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/pool/SoftReferenceQueue.java

@@ -0,0 +1,156 @@
+/*
+ * 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.codec.kryo.pool;
+
+import java.lang.ref.SoftReference;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Queue;
+
+import com.esotericsoftware.kryo.Kryo;
+
+/**
+ * Internally uses {@link SoftReference}s for queued Kryo instances,
+ * most importantly adjusts the {@link Queue#poll() poll}
+ * behavior so that gc'ed Kryo instances are skipped.
+ * Most other methods are unsupported.
+ * <p>
+ * Copied from Kryo 3.0 to facilitate dropping back to 2.22 for Spring IO
+ * compatibility.
+ * @author Martin Grotzke
+ */
+class SoftReferenceQueue implements Queue<Kryo> {
+
+	private final Queue<SoftReference<Kryo>> delegate;
+
+	@SuppressWarnings("unchecked")
+	public SoftReferenceQueue(Queue<?> delegate) {
+		this.delegate = (Queue<SoftReference<Kryo>>) delegate;
+	}
+
+	@Override
+	public Kryo poll() {
+		Kryo res;
+		SoftReference<Kryo> ref;
+		while ((ref = delegate.poll()) != null) {
+			if ((res = ref.get()) != null) {
+				return res;
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public boolean offer(Kryo e) {
+		return delegate.offer(new SoftReference<Kryo>(e));
+	}
+
+	@Override
+	public boolean add(Kryo e) {
+		return delegate.add(new SoftReference<Kryo>(e));
+	}
+
+	@Override
+	public int size() {
+		return delegate.size();
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return delegate.isEmpty();
+	}
+
+	@Override
+	public boolean contains(Object o) {
+		return delegate.contains(o);
+	}
+
+	@Override
+	public void clear() {
+		delegate.clear();
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return delegate.equals(o);
+	}
+
+	@Override
+	public int hashCode() {
+		return delegate.hashCode();
+	}
+
+	@Override
+	public String toString() {
+		return getClass().getSimpleName() + super.toString();
+	}
+
+	@Override
+	public Iterator<Kryo> iterator() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public Kryo remove() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public Object[] toArray() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public Kryo element() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public Kryo peek() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public <T> T[] toArray(T[] a) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public boolean remove(Object o) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public boolean containsAll(Collection<?> c) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public boolean addAll(Collection<? extends Kryo> c) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public boolean removeAll(Collection<?> c) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public boolean retainAll(Collection<?> c) {
+		throw new UnsupportedOperationException();
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/codec/kryo/pool/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * The <a href="https://code.google.com/p/kryo/">Kryo Pool</a> classes.
+ * Copy/paste from Kryo 3.0
+ */
+package org.springframework.integration.codec.kryo.pool;