properly support void.class in TypeDescriptor and GenericConversionService (SPR-7281)

org.springframework.core/src/main/java/org/springframework/util/ClassUtils.java

@@ -794,7 +794,7 @@ public abstract class ClassUtils {
 	 */
 	public static Class<?> resolvePrimitiveIfNecessary(Class<?> clazz) {
 		Assert.notNull(clazz, "Class must not be null");
-		return (clazz.isPrimitive() ? primitiveTypeToWrapperMap.get(clazz) : clazz);
+		return (clazz.isPrimitive() && clazz != void.class? primitiveTypeToWrapperMap.get(clazz) : clazz);
 	}
 
 	/**
@@ -802,7 +802,7 @@ public abstract class ClassUtils {
 	 * type, assuming setting by reflection. Considers primitive wrapper
 	 * classes as assignable to the corresponding primitive types.
 	 * @param lhsType the target type
-	 * @param rhsType	the value type that should be assigned to the target type
+	 * @param rhsType the value type that should be assigned to the target type
 	 * @return if the target type is assignable from the value type
 	 * @see TypeUtils#isAssignable
 	 */

org.springframework.core/src/test/java/org/springframework/core/convert/support/GenericConversionServiceTests.java

@@ -81,6 +81,18 @@ public class GenericConversionServiceTests {
 		}
 	}
 
+	@Test
+	public void sourceTypeIsVoid() {
+		GenericConversionService conversionService = new GenericConversionService();
+		assertFalse(conversionService.canConvert(void.class, String.class));
+	}
+
+	@Test
+	public void targetTypeIsVoid() {
+		GenericConversionService conversionService = new GenericConversionService();
+		assertFalse(conversionService.canConvert(String.class, void.class));
+	}
+
 	@Test
 	public void convertNull() {
 		assertNull(conversionService.convert(null, Integer.class));