DATACMNS-233 - DomainClassConverter is now safe against null and empty Strings.

Added explicit check for null or empty String source before attempting conversion. Returning null for both cases.

spring-data-commons-core/src/main/java/org/springframework/data/repository/support/DomainClassConverter.java

@@ -27,6 +27,7 @@ import org.springframework.core.convert.converter.ConditionalGenericConverter;
 import org.springframework.core.convert.converter.ConverterRegistry;
 import org.springframework.data.repository.CrudRepository;
 import org.springframework.data.repository.core.RepositoryInformation;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link org.springframework.core.convert.converter.Converter} to convert arbitrary input into domain classes managed
@@ -60,6 +61,10 @@ public class DomainClassConverter<T extends ConversionService & ConverterRegistr
 	 */
 	public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 
+		if (source == null || !StringUtils.hasText(source.toString())) {
+			return null;
+		}
+
 		RepositoryInformation info = repositories.getRepositoryInformationFor(targetType.getType());
 
 		CrudRepository<?, Serializable> repository = repositories.getRepositoryFor(targetType.getType());

spring-data-commons-core/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java

@@ -114,6 +114,20 @@ public class DomainClassConverterUnitTests {
 		assertMatches(false);
 	}
 
+	/**
+	 * @see DATACMNS-233
+	 */
+	public void returnsNullForNullSource() {
+		assertThat(converter.convert(null, sourceDescriptor, targetDescriptor), is(nullValue()));
+	}
+
+	/**
+	 * @see DATACMNS-233
+	 */
+	public void returnsNullForEmptyStringSource() {
+		assertThat(converter.convert("", sourceDescriptor, targetDescriptor), is(nullValue()));
+	}
+
 	private void assertMatches(boolean matchExpected) {
 
 		assertThat(converter.matches(sourceDescriptor, targetDescriptor), is(matchExpected));