[hotfix] [tests] Add a lightweight test for classloading in the Kryo Serializer

flink-core/src/test/java/org/apache/flink/api/java/typeutils/runtime/kryo/KryoSerializerClassLoadingTest.java

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.flink.api.java.typeutils.runtime.kryo;
+
+import org.apache.flink.api.common.ExecutionConfig;
+import org.apache.flink.api.common.typeutils.SerializerTestBase;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.api.java.tuple.Tuple1;
+import org.apache.flink.core.testutils.CommonTestUtils;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.Serializable;
+import java.net.URL;
+import java.net.URLClassLoader;
+
+import static org.junit.Assert.fail;
+
+/**
+ * This test validates that the Kryo-based serializer handles classes with custom
+ * class loaders correctly.
+ */
+public class KryoSerializerClassLoadingTest extends SerializerTestBase<Object> {
+
+	/** Class loader for the object that is not in the test class path */
+	private static final ClassLoader CLASS_LOADER =
+			new URLClassLoader(new URL[0], KryoSerializerClassLoadingTest.class.getClassLoader());
+
+	/** An object that is not in the test class path */
+	private static final Serializable OBJECT_OUT_OF_CLASSPATH =
+			CommonTestUtils.createObjectForClassNotInClassPath(CLASS_LOADER);
+
+	// ------------------------------------------------------------------------
+
+	private ClassLoader originalClassLoader;
+
+	@Before
+	public void setupClassLoader() {
+		originalClassLoader = Thread.currentThread().getContextClassLoader();
+		Thread.currentThread().setContextClassLoader(CLASS_LOADER);
+	}
+
+	@After
+	public void restoreOriginalClassLoader() {
+		Thread.currentThread().setContextClassLoader(originalClassLoader);
+	}
+
+	// ------------------------------------------------------------------------
+
+	@Test
+	public void guardTestAssumptions() {
+		try {
+			Class.forName(OBJECT_OUT_OF_CLASSPATH.getClass().getName());
+			fail("This test's assumptions are broken");
+		}
+		catch (ClassNotFoundException ignored) {
+			// expected
+		}
+	}
+
+	// ------------------------------------------------------------------------
+
+	@Override
+	protected TypeSerializer<Object> createSerializer() {
+		return new KryoSerializer<>(Object.class, new ExecutionConfig());
+	}
+
+	@Override
+	protected int getLength() {
+		return -1;
+	}
+
+	@Override
+	protected Class<Object> getTypeClass() {
+		return Object.class;
+	}
+
+	@Override
+	protected Object[] getTestData() {
+		return new Object[] {
+				new Integer(7),
+
+				// an object whose class is not on the classpath
+				OBJECT_OUT_OF_CLASSPATH,
+
+				// an object whose class IS on the classpath with a nested object whose class
+				// is NOT on the classpath
+				new Tuple1<>(OBJECT_OUT_OF_CLASSPATH)
+		};
+	}
+
+	@Override
+	public void testInstantiate() {
+		// this serializer does not support instantiation
+	}
+}