DATACMNS-1035 - Moved CustomConversions to Spring Data Commons.

Extracted CustomConversions — whose code has largely been duplicated between the MongoDB, Couchbase and Cassandra modules — into Spring Data Commons. Store-specific extensions can now be contributed via a StoreConversions value type that carries both, store-specific default converters as well as a store-specific SimpleTypeHolder to augment the default list of simple types.

Removed SimpleTypeHolders public default constructor in favour of a protected one and a static DEFAULT instance for plain references.

Original pull request: #210.

src/main/java/org/springframework/data/convert/CustomConversions.java

@@ -0,0 +1,500 @@
+/*
+ * Copyright 2011-2017 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.data.convert;
+
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+import lombok.Value;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.springframework.core.GenericTypeResolver;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.convert.converter.ConverterFactory;
+import org.springframework.core.convert.converter.GenericConverter;
+import org.springframework.core.convert.converter.GenericConverter.ConvertiblePair;
+import org.springframework.core.convert.support.GenericConversionService;
+import org.springframework.data.mapping.model.SimpleTypeHolder;
+import org.springframework.data.util.Optionals;
+import org.springframework.data.util.Streamable;
+import org.springframework.util.Assert;
+
+/**
+ * Value object to capture custom conversion. That is essentially a {@link List} of converters and some additional logic
+ * around them. The converters build up two sets of types which store-specific basic types can be converted into and
+ * from. These types will be considered simple ones (which means they neither need deeper inspection nor nested
+ * conversion. Thus the {@link CustomConversions} also act as factory for {@link SimpleTypeHolder} .
+ * 
+ * @author Oliver Gierke
+ * @author Thomas Darimont
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @since 2.0
+ */
+@Slf4j
+public class CustomConversions {
+
+	private static final String READ_CONVERTER_NOT_SIMPLE = "Registering converter from %s to %s as reading converter although it doesn't convert from a store-supported type! You might wanna check you annotation setup at the converter implementation.";
+	private static final String WRITE_CONVERTER_NOT_SIMPLE = "Registering converter from %s to %s as writing converter although it doesn't convert to a store-supported type! You might wanna check you annotation setup at the converter implementation.";
+	private static final String NOT_A_CONVERTER = "Converter %s is neither a Spring Converter, GenericConverter or ConverterFactory!";
+	private static final List<Object> DEFAULT_CONVERTERS;
+
+	static {
+
+		List<Object> defaults = new ArrayList<>();
+
+		defaults.addAll(JodaTimeConverters.getConvertersToRegister());
+		defaults.addAll(Jsr310Converters.getConvertersToRegister());
+		defaults.addAll(ThreeTenBackPortConverters.getConvertersToRegister());
+
+		DEFAULT_CONVERTERS = Collections.unmodifiableList(defaults);
+	}
+
+	private final Set<ConvertiblePair> readingPairs;
+	private final Set<ConvertiblePair> writingPairs;
+	private final Set<Class<?>> customSimpleTypes;
+	private final SimpleTypeHolder simpleTypeHolder;
+
+	private final List<Object> converters;
+
+	private final Map<ConvertiblePair, Optional<Class<?>>> customReadTargetTypes;
+	private final Map<ConvertiblePair, Optional<Class<?>>> customWriteTargetTypes;
+	private final Map<Class<?>, Optional<Class<?>>> rawWriteTargetTypes;
+
+	/**
+	 * Creates a new {@link CustomConversions} instance registering the given converters.
+	 * 
+	 * @param converters
+	 */
+	public CustomConversions(StoreConversions storeConversions, List<?> converters) {
+
+		Assert.notNull(converters, "List of converters must not be null!");
+
+		this.readingPairs = new LinkedHashSet<>();
+		this.writingPairs = new LinkedHashSet<>();
+		this.customSimpleTypes = new HashSet<>();
+		this.customReadTargetTypes = new ConcurrentHashMap<>();
+		this.customWriteTargetTypes = new ConcurrentHashMap<>();
+		this.rawWriteTargetTypes = new ConcurrentHashMap<>();
+
+		List<Object> toRegister = new ArrayList<Object>();
+
+		// Add user provided converters to make sure they can override the defaults
+		toRegister.addAll(converters);
+		toRegister.addAll(storeConversions.getStoreConverters());
+		toRegister.addAll(DEFAULT_CONVERTERS);
+
+		toRegister.stream()//
+				.flatMap(it -> storeConversions.getRegistrationsFor(it).stream())//
+				.forEach(this::register);
+
+		Collections.reverse(toRegister);
+
+		this.converters = Collections.unmodifiableList(toRegister);
+		this.simpleTypeHolder = new SimpleTypeHolder(customSimpleTypes, storeConversions.getStoreTypeHolder());
+	}
+
+	/**
+	 * Returns the underlying {@link SimpleTypeHolder}.
+	 * 
+	 * @return
+	 */
+	public SimpleTypeHolder getSimpleTypeHolder() {
+		return simpleTypeHolder;
+	}
+
+	/**
+	 * Returns whether the given type is considered to be simple. That means it's either a general simple type or we have
+	 * a writing {@link Converter} registered for a particular type.
+	 * 
+	 * @see SimpleTypeHolder#isSimpleType(Class)
+	 * @param type
+	 * @return
+	 */
+	public boolean isSimpleType(Class<?> type) {
+
+		Assert.notNull(type, "Type must not be null!");
+
+		return simpleTypeHolder.isSimpleType(type);
+	}
+
+	/**
+	 * Populates the given {@link GenericConversionService} with the converters registered.
+	 * 
+	 * @param conversionService
+	 */
+	public void registerConvertersIn(GenericConversionService conversionService) {
+
+		Assert.notNull(conversionService, "ConversionService must not be null!");
+
+		converters.forEach(it -> {
+
+			boolean added = false;
+
+			if (it instanceof Converter) {
+				conversionService.addConverter(Converter.class.cast(it));
+				added = true;
+			}
+
+			if (it instanceof ConverterFactory) {
+				conversionService.addConverterFactory(ConverterFactory.class.cast(it));
+				added = true;
+			}
+
+			if (it instanceof GenericConverter) {
+				conversionService.addConverter(GenericConverter.class.cast(it));
+				added = true;
+			}
+
+			if (!added) {
+				throw new IllegalArgumentException(String.format(NOT_A_CONVERTER, it));
+			}
+		});
+	}
+
+	/**
+	 * Registers the given {@link ConvertiblePair} as reading or writing pair depending on the type sides being basic
+	 * Mongo types.
+	 * 
+	 * @param pair
+	 */
+	private void register(ConverterRegistration converterRegistration) {
+
+		Assert.notNull(converterRegistration, "Converter registration must not be null!");
+
+		ConvertiblePair pair = converterRegistration.getConvertiblePair();
+
+		if (converterRegistration.isReading()) {
+
+			readingPairs.add(pair);
+
+			if (LOG.isWarnEnabled() && !converterRegistration.isSimpleSourceType()) {
+				LOG.warn(String.format(READ_CONVERTER_NOT_SIMPLE, pair.getSourceType(), pair.getTargetType()));
+			}
+		}
+
+		if (converterRegistration.isWriting()) {
+
+			writingPairs.add(pair);
+			customSimpleTypes.add(pair.getSourceType());
+
+			if (LOG.isWarnEnabled() && !converterRegistration.isSimpleTargetType()) {
+				LOG.warn(String.format(WRITE_CONVERTER_NOT_SIMPLE, pair.getSourceType(), pair.getTargetType()));
+			}
+		}
+	}
+
+	/**
+	 * Returns the target type to convert to in case we have a custom conversion registered to convert the given source
+	 * type into a Mongo native one.
+	 * 
+	 * @param sourceType must not be {@literal null}
+	 * @return
+	 */
+	public Optional<Class<?>> getCustomWriteTarget(Class<?> sourceType) {
+
+		Assert.notNull(sourceType, "Source type must not be null!");
+
+		return rawWriteTargetTypes.computeIfAbsent(sourceType,
+				it -> getCustomTarget(sourceType, Optional.empty(), writingPairs));
+	}
+
+	/**
+	 * Returns the target type we can readTargetWriteLocl an inject of the given source type to. The returned type might
+	 * be a subclass of the given expected type though. If {@code expectedTargetType} is {@literal null} we will simply
+	 * return the first target type matching or {@literal null} if no conversion can be found.
+	 * 
+	 * @param sourceType must not be {@literal null}
+	 * @param requestedTargetType must not be {@literal null}.
+	 * @return
+	 */
+	public Optional<Class<?>> getCustomWriteTarget(Class<?> sourceType, Class<?> requestedTargetType) {
+
+		Assert.notNull(sourceType, "Source type must not be null!");
+		Assert.notNull(requestedTargetType, "Target type must not be null!");
+
+		return customWriteTargetTypes.computeIfAbsent(new ConvertiblePair(sourceType, requestedTargetType),
+				it -> getCustomTarget(sourceType, Optional.of(requestedTargetType), writingPairs));
+	}
+
+	/**
+	 * Returns whether we have a custom conversion registered to readTargetWriteLocl into a Mongo native type. The
+	 * returned type might be a subclass of the given expected type though.
+	 * 
+	 * @param sourceType must not be {@literal null}
+	 * @return
+	 */
+	public boolean hasCustomWriteTarget(Class<?> sourceType) {
+
+		Assert.notNull(sourceType, "Source type must not be null!");
+
+		return getCustomWriteTarget(sourceType).isPresent();
+	}
+
+	/**
+	 * Returns whether we have a custom conversion registered to readTargetWriteLocl an object of the given source type
+	 * into an object of the given Mongo native target type.
+	 * 
+	 * @param sourceType must not be {@literal null}.
+	 * @param targetType must not be {@literal null}.
+	 * @return
+	 */
+	public boolean hasCustomWriteTarget(Class<?> sourceType, Class<?> targetType) {
+
+		Assert.notNull(sourceType, "Source type must not be null!");
+		Assert.notNull(targetType, "Target type must not be null!");
+
+		return getCustomWriteTarget(sourceType, targetType).isPresent();
+	}
+
+	/**
+	 * Returns whether we have a custom conversion registered to readTargetReadLock the given source into the given target
+	 * type.
+	 * 
+	 * @param sourceType must not be {@literal null}
+	 * @param targetType must not be {@literal null}
+	 * @return
+	 */
+	public boolean hasCustomReadTarget(Class<?> sourceType, Class<?> targetType) {
+
+		Assert.notNull(sourceType, "Source type must not be null!");
+		Assert.notNull(targetType, "Target type must not be null!");
+
+		return getCustomReadTarget(sourceType, targetType).isPresent();
+	}
+
+	/**
+	 * Returns the actual target type for the given {@code sourceType} and {@code requestedTargetType}. Note that the
+	 * returned {@link Class} could be an assignable type to the given {@code requestedTargetType}.
+	 * 
+	 * @param sourceType must not be {@literal null}.
+	 * @param targetType must not be {@literal null}.
+	 * @return
+	 */
+	private Optional<Class<?>> getCustomReadTarget(Class<?> sourceType, Class<?> targetType) {
+
+		return customReadTargetTypes.computeIfAbsent(new ConvertiblePair(sourceType, targetType),
+				it -> getCustomTarget(sourceType, Optional.of(targetType), readingPairs));
+	}
+
+	/**
+	 * Inspects the given {@link ConvertiblePair}s for ones that have a source compatible type as source. Additionally
+	 * checks assignability of the target type if one is given.
+	 * 
+	 * @param sourceType must not be {@literal null}.
+	 * @param targetType can be {@literal null}.
+	 * @param pairs must not be {@literal null}.
+	 * @return
+	 */
+	private static Optional<Class<?>> getCustomTarget(Class<?> sourceType, Optional<Class<?>> targetType,
+			Collection<ConvertiblePair> pairs) {
+
+		Assert.notNull(sourceType, "Source Class must not be null!");
+		Assert.notNull(pairs, "Collection of ConvertiblePair must not be null!");
+
+		return Optionals.firstNonEmpty(//
+				() -> targetType.filter(it -> pairs.contains(new ConvertiblePair(sourceType, it))), //
+				() -> pairs.stream()//
+						.filter(it -> hasAssignableSourceType(it, sourceType)) //
+						.<Class<?>> map(ConvertiblePair::getTargetType)//
+						.filter(it -> requestTargetTypeIsAssignable(targetType, it))//
+						.findFirst());
+	}
+
+	private static boolean hasAssignableSourceType(ConvertiblePair pair, Class<?> sourceType) {
+		return pair.getSourceType().isAssignableFrom(sourceType);
+	}
+
+	private static boolean requestTargetTypeIsAssignable(Optional<Class<?>> requestedTargetType, Class<?> targetType) {
+
+		return !requestedTargetType.isPresent() //
+				? true //
+				: requestedTargetType.map(it -> targetType.isAssignableFrom(it)).orElse(false);
+	}
+
+	/**
+	 * Conversion registration information.
+	 * 
+	 * @author Oliver Gierke
+	 * @author Mark Paluch
+	 */
+	@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
+	private static class ConverterRegistration {
+
+		private final @NonNull ConvertiblePair convertiblePair;
+		private final @NonNull StoreConversions storeConversions;
+		private final boolean reading;
+		private final boolean writing;
+
+		/**
+		 * Returns whether the converter shall be used for writing.
+		 * 
+		 * @return
+		 */
+		public boolean isWriting() {
+			return writing == true || (!reading && isSimpleTargetType());
+		}
+
+		/**
+		 * Returns whether the converter shall be used for reading.
+		 * 
+		 * @return
+		 */
+		public boolean isReading() {
+			return reading == true || (!writing && isSimpleSourceType());
+		}
+
+		/**
+		 * Returns the actual conversion pair.
+		 * 
+		 * @return
+		 */
+		public ConvertiblePair getConvertiblePair() {
+			return convertiblePair;
+		}
+
+		/**
+		 * Returns whether the source type is a Mongo simple one.
+		 * 
+		 * @return
+		 */
+		public boolean isSimpleSourceType() {
+			return storeConversions.isStoreSimpleType(convertiblePair.getSourceType());
+		}
+
+		/**
+		 * Returns whether the target type is a Mongo simple one.
+		 * 
+		 * @return
+		 */
+		public boolean isSimpleTargetType() {
+			return storeConversions.isStoreSimpleType(convertiblePair.getTargetType());
+		}
+	}
+
+	/**
+	 * Value type to capture store-specific extensions to the {@link CustomConversions}. Allows to forward store specific
+	 * default conversions and a set of types that are supposed to be considered simple.
+	 *
+	 * @author Oliver Gierke
+	 */
+	@Value
+	@Getter(AccessLevel.PACKAGE)
+	@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
+	public static class StoreConversions {
+
+		public static final StoreConversions NONE = StoreConversions.of(SimpleTypeHolder.DEFAULT, Collections.emptyList());
+
+		SimpleTypeHolder storeTypeHolder;
+		Collection<?> storeConverters;
+
+		/**
+		 * Creates a new {@link StoreConversions} for the given store-specific {@link SimpleTypeHolder} and the given
+		 * converters.
+		 * 
+		 * @param storeTypeHolder must not be {@literal null}.
+		 * @param converters must not be {@literal null}.
+		 * @return
+		 */
+		public static StoreConversions of(SimpleTypeHolder storeTypeHolder, Object... converters) {
+
+			Assert.notNull(storeTypeHolder, "SimpleTypeHolder must not be null!");
+			Assert.notNull(converters, "Converters must not be null!");
+
+			return new StoreConversions(storeTypeHolder, Arrays.asList(converters));
+		}
+
+		/**
+		 * Creates a new {@link StoreConversions} for the given store-specific {@link SimpleTypeHolder} and the given
+		 * converters.
+		 * 
+		 * @param storeTypeHolder must not be {@literal null}.
+		 * @param converters must not be {@literal null}.
+		 * @return
+		 */
+		public static StoreConversions of(SimpleTypeHolder storeTypeHolder, Collection<?> converters) {
+
+			Assert.notNull(storeTypeHolder, "SimpleTypeHolder must not be null!");
+			Assert.notNull(converters, "Converters must not be null!");
+
+			return new StoreConversions(storeTypeHolder, converters);
+		}
+
+		/**
+		 * Returns {@link ConverterRegistration}s for the given converter.
+		 * 
+		 * @param converter must not be {@literal null}.
+		 * @return
+		 */
+		public Streamable<ConverterRegistration> getRegistrationsFor(Object converter) {
+
+			Assert.notNull(converter, "Converter must not be null!");
+
+			Class<?> type = converter.getClass();
+			boolean isWriting = type.isAnnotationPresent(WritingConverter.class);
+			boolean isReading = type.isAnnotationPresent(ReadingConverter.class);
+
+			if (converter instanceof GenericConverter) {
+
+				GenericConverter genericConverter = (GenericConverter) converter;
+				return Streamable.of(genericConverter.getConvertibleTypes()).map(it -> register(it, isReading, isWriting));
+
+			} else if (converter instanceof ConverterFactory) {
+
+				return getRegistrationFor(converter, ConverterFactory.class, isReading, isWriting);
+
+			} else if (converter instanceof Converter) {
+
+				return getRegistrationFor(converter, Converter.class, isReading, isWriting);
+
+			} else {
+				throw new IllegalArgumentException("Unsupported converter type!");
+			}
+		}
+
+		private Streamable<ConverterRegistration> getRegistrationFor(Object converter, Class<?> type, boolean isReading,
+				boolean isWriting) {
+
+			Class<?>[] arguments = GenericTypeResolver.resolveTypeArguments(converter.getClass(), type);
+			return Streamable.of(register(arguments[0], arguments[1], isReading, isWriting));
+		}
+
+		private ConverterRegistration register(Class<?> source, Class<?> target, boolean isReading, boolean isWriting) {
+			return register(new ConvertiblePair(source, target), isReading, isWriting);
+		}
+
+		private ConverterRegistration register(ConvertiblePair pair, boolean isReading, boolean isWriting) {
+			return new ConverterRegistration(pair, this, isReading, isWriting);
+		}
+
+		private boolean isStoreSimpleType(Class<?> type) {
+			return storeTypeHolder.isSimpleType(type);
+		}
+	}
+}

src/main/java/org/springframework/data/mapping/context/AbstractMappingContext.java

@@ -89,7 +89,7 @@ public abstract class AbstractMappingContext<E extends MutablePersistentEntity<?
 
 	private Set<? extends Class<?>> initialEntitySet = new HashSet<>();
 	private boolean strict = false;
-	private SimpleTypeHolder simpleTypeHolder = new SimpleTypeHolder();
+	private SimpleTypeHolder simpleTypeHolder = SimpleTypeHolder.DEFAULT;
 
 	private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
 	private final Lock read = lock.readLock();

src/main/java/org/springframework/data/mapping/model/SimpleTypeHolder.java

@@ -32,39 +32,43 @@ import org.springframework.util.Assert;
  */
 public class SimpleTypeHolder {
 
-	private static final Set<Class<?>> DEFAULTS = new HashSet<>();
-
-	static {
-		DEFAULTS.add(boolean.class);
-		DEFAULTS.add(boolean[].class);
-		DEFAULTS.add(long.class);
-		DEFAULTS.add(long[].class);
-		DEFAULTS.add(short.class);
-		DEFAULTS.add(short[].class);
-		DEFAULTS.add(int.class);
-		DEFAULTS.add(int[].class);
-		DEFAULTS.add(byte.class);
-		DEFAULTS.add(byte[].class);
-		DEFAULTS.add(float.class);
-		DEFAULTS.add(float[].class);
-		DEFAULTS.add(double.class);
-		DEFAULTS.add(double[].class);
-		DEFAULTS.add(char.class);
-		DEFAULTS.add(char[].class);
-		DEFAULTS.add(Boolean.class);
-		DEFAULTS.add(Long.class);
-		DEFAULTS.add(Short.class);
-		DEFAULTS.add(Integer.class);
-		DEFAULTS.add(Byte.class);
-		DEFAULTS.add(Float.class);
-		DEFAULTS.add(Double.class);
-		DEFAULTS.add(Character.class);
-		DEFAULTS.add(String.class);
-		DEFAULTS.add(Date.class);
-		DEFAULTS.add(Locale.class);
-		DEFAULTS.add(Class.class);
-		DEFAULTS.add(Enum.class);
-	}
+	private static final Set<Class<?>> DEFAULTS = new HashSet<Class<?>>() {
+
+		private static final long serialVersionUID = -1738594126505221500L;
+
+		{
+			add(boolean.class);
+			add(boolean[].class);
+			add(long.class);
+			add(long[].class);
+			add(short.class);
+			add(short[].class);
+			add(int.class);
+			add(int[].class);
+			add(byte.class);
+			add(byte[].class);
+			add(float.class);
+			add(float[].class);
+			add(double.class);
+			add(double[].class);
+			add(char.class);
+			add(char[].class);
+			add(Boolean.class);
+			add(Long.class);
+			add(Short.class);
+			add(Integer.class);
+			add(Byte.class);
+			add(Float.class);
+			add(Double.class);
+			add(Character.class);
+			add(String.class);
+			add(Date.class);
+			add(Locale.class);
+			add(Class.class);
+			add(Enum.class);
+		}
+	};
+	public static final SimpleTypeHolder DEFAULT = new SimpleTypeHolder();
 
 	private final Set<Class<?>> simpleTypes;
 
@@ -73,8 +77,7 @@ public class SimpleTypeHolder {
 	 * 
 	 * @see #SimpleTypeHolder(Set, boolean)
 	 */
-	@SuppressWarnings("unchecked")
-	public SimpleTypeHolder() {
+	protected SimpleTypeHolder() {
 		this(Collections.emptySet(), true);
 	}
 
@@ -128,13 +131,8 @@ public class SimpleTypeHolder {
 			return true;
 		}
 
-		for (Class<?> clazz : simpleTypes) {
-			if (clazz.isAssignableFrom(type)) {
-				simpleTypes.add(type);
-				return true;
-			}
-		}
-
-		return false;
+		return simpleTypes.stream()//
+				.filter(it -> it.isAssignableFrom(type))//
+				.peek(it -> simpleTypes.add(type)).findFirst().isPresent();
 	}
 }

src/test/java/org/springframework/data/convert/CustomConversionsUnitTests.java

@@ -0,0 +1,277 @@
+/*
+ * Copyright 2011-2017 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.data.convert;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.assertThat;
+
+import java.text.DateFormat;
+import java.text.Format;
+import java.text.SimpleDateFormat;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Date;
+import java.util.Locale;
+
+import org.joda.time.DateTime;
+import org.junit.Test;
+import org.springframework.aop.framework.ProxyFactory;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.convert.converter.ConverterFactory;
+import org.springframework.core.convert.support.DefaultConversionService;
+import org.springframework.core.convert.support.GenericConversionService;
+import org.springframework.data.convert.CustomConversions.StoreConversions;
+import org.threeten.bp.LocalDateTime;
+
+/**
+ * Unit tests for {@link MongoCustomConversions}.
+ * 
+ * @author Oliver Gierke
+ * @author Christoph Strobl
+ * @since 2.0
+ */
+public class CustomConversionsUnitTests {
+
+	@Test // DATACMNS-1035
+	public void findsBasicReadAndWriteConversions() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(FormatToStringConverter.INSTANCE, StringToFormatConverter.INSTANCE));
+
+		assertThat(conversions.getCustomWriteTarget(Format.class)).hasValue(String.class);
+		assertThat(conversions.getCustomWriteTarget(String.class)).isNotPresent();
+
+		assertThat(conversions.hasCustomReadTarget(String.class, Format.class)).isTrue();
+		assertThat(conversions.hasCustomReadTarget(String.class, Locale.class)).isFalse();
+	}
+
+	@Test // DATACMNS-1035
+	public void considersSubtypesCorrectly() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(NumberToStringConverter.INSTANCE, StringToNumberConverter.INSTANCE));
+
+		assertThat(conversions.getCustomWriteTarget(Long.class)).hasValue(String.class);
+		assertThat(conversions.hasCustomReadTarget(String.class, Long.class)).isTrue();
+	}
+
+	@Test // DATACMNS-1035
+	public void populatesConversionServiceCorrectly() {
+
+		GenericConversionService conversionService = new DefaultConversionService();
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(StringToFormatConverter.INSTANCE));
+		conversions.registerConvertersIn(conversionService);
+
+		assertThat(conversionService.canConvert(String.class, Format.class), is(true));
+	}
+
+	@Test // DATAMONGO-259, DATACMNS-1035
+	public void doesNotConsiderTypeSimpleIfOnlyReadConverterIsRegistered() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(StringToFormatConverter.INSTANCE));
+		assertThat(conversions.isSimpleType(Format.class), is(false));
+	}
+
+	@Test // DATAMONGO-298, DATACMNS-1035
+	public void discoversConvertersForSubtypesOfMongoTypes() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(StringToIntegerConverter.INSTANCE));
+		assertThat(conversions.hasCustomReadTarget(String.class, Integer.class), is(true));
+		assertThat(conversions.hasCustomWriteTarget(String.class, Integer.class), is(true));
+	}
+
+	@Test // DATAMONGO-795, DATACMNS-1035
+	public void favorsCustomConverterForIndeterminedTargetType() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(DateTimeToStringConverter.INSTANCE));
+		assertThat(conversions.getCustomWriteTarget(DateTime.class)).hasValue(String.class);
+	}
+
+	@Test // DATAMONGO-881, DATACMNS-1035
+	public void customConverterOverridesDefault() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(CustomDateTimeConverter.INSTANCE));
+		GenericConversionService conversionService = new DefaultConversionService();
+		conversions.registerConvertersIn(conversionService);
+
+		assertThat(conversionService.convert(new DateTime(), Date.class)).isEqualTo(new Date(0));
+	}
+
+	@Test // DATAMONGO-1001, DATACMNS-1035
+	public void shouldSelectPropertCustomWriteTargetForCglibProxiedType() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(FormatToStringConverter.INSTANCE));
+		assertThat(conversions.getCustomWriteTarget(createProxyTypeFor(Format.class))).hasValue(String.class);
+	}
+
+	@Test // DATAMONGO-1001, DATACMNS-1035
+	public void shouldSelectPropertCustomReadTargetForCglibProxiedType() {
+
+		CustomConversions conversions = new CustomConversions(StoreConversions.NONE,
+				Arrays.asList(CustomObjectToStringConverter.INSTANCE));
+		assertThat(conversions.hasCustomReadTarget(createProxyTypeFor(Object.class), String.class)).isTrue();
+	}
+
+	@Test // DATAMONGO-1131, DATACMNS-1035
+	public void registersConvertersForJsr310() {
+
+		CustomConversions customConversions = new CustomConversions(StoreConversions.NONE, Collections.emptyList());
+
+		assertThat(customConversions.hasCustomWriteTarget(java.time.LocalDateTime.class)).isTrue();
+	}
+
+	@Test // DATAMONGO-1131, DATACMNS-1035
+	public void registersConvertersForThreeTenBackPort() {
+
+		CustomConversions customConversions = new CustomConversions(StoreConversions.NONE, Collections.emptyList());
+
+		assertThat(customConversions.hasCustomWriteTarget(LocalDateTime.class)).isTrue();
+	}
+
+	@Test // DATAMONGO-1302, DATACMNS-1035
+	public void registersConverterFactoryCorrectly() {
+
+		CustomConversions customConversions = new CustomConversions(StoreConversions.NONE,
+				Collections.singletonList(new FormatConverterFactory()));
+
+		assertThat(customConversions.getCustomWriteTarget(String.class, SimpleDateFormat.class)).isPresent();
+	}
+
+	private static Class<?> createProxyTypeFor(Class<?> type) {
+
+		ProxyFactory factory = new ProxyFactory();
+		factory.setProxyTargetClass(true);
+		factory.setTargetClass(type);
+
+		return factory.getProxy().getClass();
+	}
+
+	enum FormatToStringConverter implements Converter<Format, String> {
+
+		INSTANCE;
+
+		public String convert(Format source) {
+			return source.toString();
+		}
+	}
+
+	enum StringToFormatConverter implements Converter<String, Format> {
+
+		INSTANCE;
+
+		public Format convert(String source) {
+			return DateFormat.getInstance();
+		}
+	}
+
+	enum NumberToStringConverter implements Converter<Number, String> {
+
+		INSTANCE;
+
+		public String convert(Number source) {
+			return source.toString();
+		}
+	}
+
+	enum StringToNumberConverter implements Converter<String, Number> {
+
+		INSTANCE;
+
+		public Number convert(String source) {
+			return 0L;
+		}
+	}
+
+	enum StringToIntegerConverter implements Converter<String, Integer> {
+
+		INSTANCE;
+
+		public Integer convert(String source) {
+			return 0;
+		}
+	}
+
+	enum DateTimeToStringConverter implements Converter<DateTime, String> {
+
+		INSTANCE;
+
+		@Override
+		public String convert(DateTime source) {
+			return "";
+		}
+	}
+
+	enum CustomDateTimeConverter implements Converter<DateTime, Date> {
+
+		INSTANCE;
+
+		@Override
+		public Date convert(DateTime source) {
+			return new Date(0);
+		}
+	}
+
+	enum CustomObjectToStringConverter implements Converter<Object, String> {
+
+		INSTANCE;
+
+		@Override
+		public String convert(Object source) {
+			return source != null ? source.toString() : null;
+		}
+
+	}
+
+	@WritingConverter
+	static class FormatConverterFactory implements ConverterFactory<String, Format> {
+
+		@Override
+		public <T extends Format> Converter<String, T> getConverter(Class<T> targetType) {
+			return new StringToFormat<T>(targetType);
+		}
+
+		private static final class StringToFormat<T extends Format> implements Converter<String, T> {
+
+			private final Class<T> targetType;
+
+			public StringToFormat(Class<T> targetType) {
+				this.targetType = targetType;
+			}
+
+			@Override
+			public T convert(String source) {
+
+				if (source.length() == 0) {
+					return null;
+				}
+
+				try {
+					return targetType.newInstance();
+				} catch (Exception e) {
+					throw new IllegalArgumentException(e.getMessage(), e);
+				}
+			}
+		}
+	}
+}

src/test/java/org/springframework/data/mapping/SimpleTypeHolderUnitTests.java

@@ -44,14 +44,14 @@ public class SimpleTypeHolderUnitTests {
 
 	@Test(expected = IllegalArgumentException.class) // DATACMNS-31
 	public void rejectsNullTypeForIsSimpleTypeCall() {
-		SimpleTypeHolder holder = new SimpleTypeHolder();
+		SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 		holder.isSimpleType(null);
 	}
 
 	@Test
 	public void addsDefaultTypes() {
 
-		SimpleTypeHolder holder = new SimpleTypeHolder();
+		SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 
 		assertThat(holder.isSimpleType(String.class)).isTrue();
 	}
@@ -87,28 +87,28 @@ public class SimpleTypeHolderUnitTests {
 
 	@Test
 	public void considersObjectToBeSimpleType() {
-		SimpleTypeHolder holder = new SimpleTypeHolder();
+		SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 		assertThat(holder.isSimpleType(Object.class)).isTrue();
 	}
 
 	@Test
 	public void considersSimpleEnumAsSimple() {
 
-		SimpleTypeHolder holder = new SimpleTypeHolder();
+		SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 		assertThat(holder.isSimpleType(SimpleEnum.FOO.getClass())).isTrue();
 	}
 
 	@Test
 	public void considersComplexEnumAsSimple() {
 
-		SimpleTypeHolder holder = new SimpleTypeHolder();
+		SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 		assertThat(holder.isSimpleType(ComplexEnum.FOO.getClass())).isTrue();
 	}
 
 	@Test // DATACMNS-1006
 	public void considersJavaLangTypesSimple() {
 
-		SimpleTypeHolder holder = new SimpleTypeHolder();
+		SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 
 		assertThat(holder.isSimpleType(Type.class)).isTrue();
 	}

src/test/java/org/springframework/data/mapping/context/AbstractMappingContextUnitTests.java

@@ -48,7 +48,7 @@ import org.springframework.util.StringUtils;
  */
 public class AbstractMappingContextUnitTests {
 
-	final SimpleTypeHolder holder = new SimpleTypeHolder();
+	final SimpleTypeHolder holder = SimpleTypeHolder.DEFAULT;
 	SampleMappingContext context;
 
 	@Before
@@ -153,7 +153,9 @@ public class AbstractMappingContextUnitTests {
 		PersistentEntity<Object, SamplePersistentProperty> entity = mappingContext
 				.getRequiredPersistentEntity(Sample.class);
 
-		assertThat(entity.getPersistentProperty("persons")).hasValueSatisfying(it -> assertThat(mappingContext.getPersistentEntity(it)).hasValueSatisfying(inner -> assertThat(inner.getType()).isEqualTo(Person.class)));
+		assertThat(entity.getPersistentProperty("persons"))
+				.hasValueSatisfying(it -> assertThat(mappingContext.getPersistentEntity(it))
+						.hasValueSatisfying(inner -> assertThat(inner.getType()).isEqualTo(Person.class)));
 	}
 
 	@Test // DATACMNS-380