DATACMNS-867 - RepositoryInvoker now returns an Optional for invokeFindOne(…).

Adapted ReflectionRepositoryInvoker to transparently unwrap other potentially used wrapper types to then convert the result into an Optional.

src/main/java/org/springframework/data/querydsl/QuerydslRepositoryInvokerAdapter.java

@@ -17,6 +17,7 @@ package org.springframework.data.querydsl;
 
 import java.io.Serializable;
 import java.lang.reflect.Method;
+import java.util.Optional;
 
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
@@ -125,7 +126,7 @@ public class QuerydslRepositoryInvokerAdapter implements RepositoryInvoker {
 	 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeFindOne(java.io.Serializable)
 	 */
 	@Override
-	public <T> T invokeFindOne(Serializable id) {
+	public <T> Optional<T> invokeFindOne(Serializable id) {
 		return delegate.invokeFindOne(id);
 	}
 

src/main/java/org/springframework/data/repository/support/CrudRepositoryInvoker.java

@@ -89,8 +89,8 @@ class CrudRepositoryInvoker extends ReflectionRepositoryInvoker {
 	 */
 	@Override
 	@SuppressWarnings("unchecked")
-	public <T> T invokeFindOne(Serializable id) {
-		return customFindOneMethod ? super.invokeFindOne(id) : (T) repository.findOne(convertId(id));
+	public <T> Optional<T> invokeFindOne(Serializable id) {
+		return customFindOneMethod ? super.invokeFindOne(id) : (Optional<T>) repository.findOne(convertId(id));
 	}
 
 	/*

src/main/java/org/springframework/data/repository/support/DomainClassConverter.java

@@ -152,11 +152,9 @@ public class DomainClassConverter<T extends ConversionService & ConverterRegistr
 
 			Class<?> domainType = targetType.getType();
 			RepositoryInvoker invoker = repositoryInvokerFactory.getInvokerFor(domainType);
+			RepositoryInformation information = repositories.getRequiredRepositoryInformation(domainType);
 
-			return repositories.getRepositoryInformationFor(domainType)//
-					.map(it -> invoker.invokeFindOne(conversionService.convert(source, it.getIdType())))//
-					.orElseThrow(() -> new IllegalStateException(
-							String.format("Couldn't find RepositoryInformation for %s!", domainType)));
+			return invoker.invokeFindOne(conversionService.convert(source, information.getIdType())).orElse(null);
 		}
 
 		/*

src/main/java/org/springframework/data/repository/support/ReflectionRepositoryInvoker.java

@@ -30,6 +30,7 @@ import org.springframework.data.domain.Sort;
 import org.springframework.data.repository.core.CrudMethods;
 import org.springframework.data.repository.core.RepositoryMetadata;
 import org.springframework.data.repository.query.Param;
+import org.springframework.data.repository.util.QueryExecutionConverters;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.MultiValueMap;
@@ -135,12 +136,23 @@ class ReflectionRepositoryInvoker implements RepositoryInvoker {
 	 * @see org.springframework.data.rest.core.invoke.RepositoryInvoker#invokeFindOne(java.io.Serializable)
 	 */
 	@Override
-	public <T> T invokeFindOne(Serializable id) {
+	@SuppressWarnings("unchecked")
+	public <T> Optional<T> invokeFindOne(Serializable id) {
 
 		Method method = methods.getFindOneMethod()//
 				.orElseThrow(() -> new IllegalStateException("Repository doesn't have a find-one-method declared!"));
 
-		return invoke(method, convertId(id));
+		Object invoke = invoke(method, convertId(id));
+
+		if (Optional.class.isInstance(invoke)) {
+			return (Optional<T>) invoke;
+		}
+
+		if (invoke == null) {
+			return Optional.empty();
+		}
+
+		return conversionService.convert(QueryExecutionConverters.unwrap(invoke), Optional.class);
 	}
 
 	/* 
@@ -169,7 +181,7 @@ class ReflectionRepositoryInvoker implements RepositoryInvoker {
 		if (idTypes.contains(parameterType)) {
 			invoke(method, convertId(id));
 		} else {
-			invoke(method, this.<Object>invokeFindOne(id));
+			invoke(method, this.<Object> invokeFindOne(id).orElse(null));
 		}
 	}
 

src/main/java/org/springframework/data/repository/support/RepositoryInvoker.java

@@ -17,6 +17,7 @@ package org.springframework.data.repository.support;
 
 import java.io.Serializable;
 import java.lang.reflect.Method;
+import java.util.Optional;
 
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
@@ -49,7 +50,7 @@ public interface RepositoryInvoker extends RepositoryInvocationInformation {
 	 * @return the entity with the given id.
 	 * @throws IllegalStateException if the repository does not expose a find-one-method.
 	 */
-	<T> T invokeFindOne(Serializable id);
+	<T> Optional<T> invokeFindOne(Serializable id);
 
 	/**
 	 * Invokes the find-all method of the underlying repository using the method taking a {@link Pageable} as parameter if