DATACMNS-782 - ProxyProjectionFactory now converts primitive attribute values.

The ProjectingMethodInterceptor now uses a default ConversionService instance to try to convert a potentially not matching result of the target invocation into the type the projection requires before the attempt to create nested projection.

src/main/java/org/springframework/data/projection/ProjectingMethodInterceptor.java

@@ -26,6 +26,8 @@ import java.util.Map.Entry;
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 import org.springframework.core.CollectionFactory;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.data.util.ClassTypeInformation;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.Assert;
@@ -43,6 +45,7 @@ class ProjectingMethodInterceptor implements MethodInterceptor {
 
 	private final ProjectionFactory factory;
 	private final MethodInterceptor delegate;
+	private final ConversionService conversionService;
 
 	/**
 	 * Creates a new {@link ProjectingMethodInterceptor} using the given {@link ProjectionFactory} and delegate
@@ -59,6 +62,7 @@ class ProjectingMethodInterceptor implements MethodInterceptor {
 
 		this.factory = factory;
 		this.delegate = delegate;
+		this.conversionService = new DefaultConversionService();
 	}
 
 	/* 
@@ -75,13 +79,16 @@ class ProjectingMethodInterceptor implements MethodInterceptor {
 		}
 
 		TypeInformation<?> type = ClassTypeInformation.fromReturnTypeOf(invocation.getMethod());
+		Class<?> rawType = type.getType();
 
-		if (type.isCollectionLike() && !ClassUtils.isPrimitiveArray(type.getType())) {
+		if (type.isCollectionLike() && !ClassUtils.isPrimitiveArray(rawType)) {
 			return projectCollectionElements(asCollection(result), type);
 		} else if (type.isMap()) {
 			return projectMapValues((Map<?, ?>) result, type);
+		} else if (conversionRequiredAndPossible(result, rawType)) {
+			return conversionService.convert(result, rawType);
 		} else {
-			return getProjection(result, type.getType());
+			return getProjection(result, rawType);
 		}
 	}
 
@@ -134,6 +141,23 @@ class ProjectingMethodInterceptor implements MethodInterceptor {
 				: factory.createProjection(returnType, result);
 	}
 
+	/**
+	 * Returns whether the source object needs to be converted to the given target type and whether we can convert it at
+	 * all.
+	 * 
+	 * @param source can be {@literal null}.
+	 * @param targetType must not be {@literal null}.
+	 * @return
+	 */
+	private boolean conversionRequiredAndPossible(Object source, Class<?> targetType) {
+
+		if (source == null || targetType.isInstance(source)) {
+			return false;
+		}
+
+		return conversionService.canConvert(source.getClass(), targetType);
+	}
+
 	/**
 	 * Turns the given value into a {@link Collection}. Will turn an array into a collection an wrap all other values into
 	 * a single-element collection.

src/test/java/org/springframework/data/projection/ProxyProjectionFactoryUnitTests.java

@@ -157,7 +157,7 @@ public class ProxyProjectionFactoryUnitTests {
 
 		List<String> result = factory.getInputProperties(CustomerExcerpt.class);
 
-		assertThat(result, hasSize(4));
+		assertThat(result, hasSize(5));
 		assertThat(result, hasItems("firstname", "address", "shippingAddresses", "picture"));
 	}
 
@@ -220,8 +220,23 @@ public class ProxyProjectionFactoryUnitTests {
 		assertThat(excerpt.getShippingAddresses(), is(arrayWithSize(1)));
 	}
 
+	/**
+	 * @see DATACMNS-782
+	 */
+	@Test
+	public void convertsPrimitiveValues() {
+
+		Customer customer = new Customer();
+		customer.id = 1L;
+
+		CustomerExcerpt excerpt = factory.createProjection(CustomerExcerpt.class, customer);
+
+		assertThat(excerpt.getId(), is(customer.id.toString()));
+	}
+
 	static class Customer {
 
+		public Long id;
 		public String firstname, lastname;
 		public Address address;
 		public byte[] picture;
@@ -235,6 +250,8 @@ public class ProxyProjectionFactoryUnitTests {
 
 	interface CustomerExcerpt {
 
+		String getId();
+
 		String getFirstname();
 
 		AddressExcerpt getAddress();