Add PdxInstanceBuilder class used to create instances of PDX types (PdxInstance).

The Builder allows users to copy an existing PdxInstance to a new PdxInstance or create a PdxInstance from an Object.

apache-geode-extensions/src/main/java/org/springframework/geode/pdx/PdxInstanceBuilder.java

@@ -0,0 +1,203 @@
+/*
+ * Copyright 2020 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
+ *
+ *     https://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.geode.pdx;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.geode.cache.GemFireCache;
+import org.apache.geode.cache.RegionService;
+import org.apache.geode.pdx.PdxInstance;
+import org.apache.geode.pdx.PdxInstanceFactory;
+
+import org.springframework.geode.cache.SimpleCacheResolver;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * The {@link PdxInstanceBuilder} class is a <a href="https://en.wikipedia.org/wiki/Builder_pattern">Builder</a>
+ * used to construct and initialize a {@link PdxInstance} from different sources.
+ *
+ * @author John Blum
+ * @see org.apache.geode.cache.GemFireCache
+ * @see org.apache.geode.cache.RegionService
+ * @see org.apache.geode.pdx.PdxInstance
+ * @see org.apache.geode.pdx.PdxInstanceFactory
+ * @see <a href="https://en.wikipedia.org/wiki/Builder_pattern">Builder Software Design Pattern</a>
+ * @since 1.3.0
+ */
+@SuppressWarnings("unused")
+public class PdxInstanceBuilder {
+
+	/**
+	 * Factory method used to construct a new instance of the {@link PdxInstanceBuilder} class.
+	 *
+	 * This factory method tries to resolve the {@link GemFireCache} instance for the caller
+	 * by using {@link SimpleCacheResolver}.
+	 *
+	 * Alternatively, callers may provider their own {@link GemFireCache} instance by calling
+	 * {@link #create(RegionService)}.
+	 *
+	 * @return a new instance of the {@link PdxInstanceBuilder}.
+	 * @throws IllegalArgumentException if a {@link GemFireCache} instance is not present.
+	 * @see #create(RegionService)
+	 */
+	public static PdxInstanceBuilder create() {
+		return create(SimpleCacheResolver.getInstance().require());
+	}
+
+	/**
+	 * Factory method use to construct a new instance of the {@link PdxInstanceBuilder} class initialized with
+	 * the given, required {@link RegionService} used by the Builder to performs its functions.
+	 *
+	 * @param regionService {@link RegionService} instance used by the {@link PdxInstanceBuilder} to perform
+	 * its functions;
+	 * must not be {@literal null}.
+	 * @return an new instance of the {@link PdxInstanceBuilder}.
+	 * @throws IllegalArgumentException if {@link GemFireCache} is {@literal null}.
+	 * @see org.apache.geode.cache.GemFireCache
+	 * @see #PdxInstanceBuilder(RegionService)
+	 */
+	public static PdxInstanceBuilder create(RegionService regionService) {
+		return new PdxInstanceBuilder(regionService);
+	}
+
+	private static void assertNotNull(Object target, String message, Object... arguments) {
+
+		if (target == null) {
+			throw new IllegalArgumentException(String.format(message, arguments));
+		}
+	}
+
+	private static <T> List<T> nullSafeList(List<T> list) {
+		return list != null ? list : Collections.emptyList();
+	}
+
+	private final RegionService regionService;
+
+	private PdxInstanceFactory pdxFactory;
+
+	/**
+	 * Constructs a new instance of {@link PdxInstanceBuilder} initialized with the required {@link RegionService}.
+	 *
+	 * @param regionService {@link RegionService} instance used to perform the functions of the PDX Builder.
+	 * @throws IllegalArgumentException if {@link RegionService} is {@literal null}.
+	 * @see org.apache.geode.cache.RegionService
+	 */
+	protected PdxInstanceBuilder(RegionService regionService) {
+
+		assertNotNull(regionService, "RegionService must not be null");
+
+		this.regionService = regionService;
+	}
+
+	/**
+	 * Returns a reference to the configured {@link RegionService} used to perform the operations of this PDX Builder.
+	 *
+	 * @return a reference to the configured {@link RegionService}; never {@literal null}.
+	 */
+	protected RegionService getRegionService() {
+		return this.regionService;
+	}
+
+	/**
+	 * Copies the contents of the existing {@link PdxInstance} to a new {@link PdxInstance} built with this Builder.
+	 *
+	 * @param pdxInstance {@link PdxInstance} to copy.
+	 * @return an instance of the {@link PdxInstanceFactory} used to {@link PdxInstanceFactory#create() create}
+	 * the {@link PdxInstance}.
+	 * @throws IllegalArgumentException if {@link PdxInstance} is {@literal null}.
+	 * @see org.apache.geode.pdx.PdxInstance
+	 * @see org.apache.geode.pdx.PdxInstanceFactory
+	 */
+	public PdxInstanceFactory copy(PdxInstance pdxInstance) {
+
+		assertNotNull(pdxInstance, "PdxInstance must not be null");
+
+		PdxInstanceFactory factory = getRegionService().createPdxInstanceFactory(pdxInstance.getClassName());
+
+		nullSafeList(pdxInstance.getFieldNames()).forEach(fieldName -> {
+
+			factory.writeObject(fieldName, pdxInstance.getField(fieldName));
+
+			if (pdxInstance.isIdentityField(fieldName)) {
+				factory.markIdentityField(fieldName);
+			}
+		});
+
+		return factory;
+	}
+
+	/**
+	 * Constructs a new {@link PdxInstance} from the given, required source {@link Object}.
+	 *
+	 * @param source {@link Object} being serialized to PDX; must not be {@literal null}.
+	 * @return a {@link Factory} used to create the {@link PdxInstance} from the given,
+	 * required source {@link Object}, which was serialized to PDX.
+	 * @throws IllegalArgumentException if {@link Object source} is {@literal null}.
+	 * @see Factory
+	 */
+	public Factory from(Object source) {
+
+		assertNotNull(source, "Source object to serialize to PDX must not be null");
+
+		RegionService regionService = getRegionService();
+
+		Optional.of(regionService)
+			.filter(GemFireCache.class::isInstance)
+			.map(GemFireCache.class::cast)
+			.map(GemFireCache::getPdxReadSerialized)
+			.filter(Boolean.TRUE::equals)
+			.orElseThrow(() -> new IllegalStateException("PDX read-serialized must be set to true"));
+
+		PdxInstanceFactory factory = regionService.createPdxInstanceFactory(source.getClass().getName());
+
+		factory.writeObject("source", source);
+
+		AtomicReference<Object> resolvedSource = new AtomicReference<>(null);
+
+		return () -> Optional.of(factory)
+			.map(PdxInstanceFactory::create)
+			.map(pdxInstance -> resolvedSource.updateAndGet(it -> pdxInstance.getField("source")))
+			.filter(PdxInstance.class::isInstance)
+			.map(PdxInstance.class::cast)
+			.orElseThrow(() -> {
+
+				String message = String.format("Expected an instance of PDX but was an instance of type [%s];"
+						+ " Was PDX read-serialized set to true", ObjectUtils.nullSafeClassName(resolvedSource.get()));
+
+				return new IllegalArgumentException(message);
+			});
+	}
+
+	@FunctionalInterface
+	public interface Factory {
+
+		/**
+		 * Creates a {@link PdxInstance}.
+		 *
+		 * @return the created {@link PdxInstance}.
+		 * @throws IllegalArgumentException Depending on the implementation, an {@link IllegalArgumentException}
+		 * may be thrown if the {@link Object created object} is not of type {@link PdxInstance}.
+		 * @throws ClassCastException Depending on the implementation, a {@link ClassCastException} may be thrown
+		 * if the {@link Object created object} is not of type {@link PdxInstance}.
+		 * @see org.apache.geode.pdx.PdxInstance
+		 */
+		PdxInstance create();
+
+	}
+}