DATAMONGO-1034 - Explicitly reject incompatible types in MappingMongoConverter.

Improved the exception message that is occurs if the source document contains a BasicDBList but has to be converted into a complex object. We now explicitly hint to use a custom Converter to manually.

Improved toString() method on ObjectPath to create more helpful output.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java

@@ -76,6 +76,8 @@ import com.mongodb.DBRef;
  */
 public class MappingMongoConverter extends AbstractMongoConverter implements ApplicationContextAware, ValueResolver {
 
+	private static final String INCOMPATIBLE_TYPES = "Cannot convert %1$s of type %2$s into an instance of %3$s! Implement a custom Converter<%2$s, %3$s> and register it with the CustomConversions. Parent object was: %4$s";
+
 	protected static final Logger LOGGER = LoggerFactory.getLogger(MappingMongoConverter.class);
 
 	protected final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
@@ -214,6 +216,10 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			return (S) readMap(typeToUse, dbo, path);
 		}
 
+		if (dbo instanceof BasicDBList) {
+			throw new MappingException(String.format(INCOMPATIBLE_TYPES, dbo, BasicDBList.class, typeToUse.getType(), path));
+		}
+
 		// Retrieve persistent entity info
 		MongoPersistentEntity<S> persistentEntity = (MongoPersistentEntity<S>) mappingContext
 				.getPersistentEntity(typeToUse);

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/ObjectPath.java

@@ -21,6 +21,7 @@ import java.util.List;
 
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 import com.mongodb.DBObject;
 
@@ -120,6 +121,26 @@ class ObjectPath {
 		return items.isEmpty() ? null : items.get(items.size() - 1).getObject();
 	}
 
+	/* 
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
+	@Override
+	public String toString() {
+
+		if (items.isEmpty()) {
+			return "[empty]";
+		}
+
+		List<String> strings = new ArrayList<String>(items.size());
+
+		for (ObjectPathItem item : items) {
+			strings.add(item.object.toString());
+		}
+
+		return StringUtils.collectionToDelimitedString(strings, " -> ");
+	}
+
 	/**
 	 * An item in an {@link ObjectPath}.
 	 * 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java

@@ -45,7 +45,9 @@ import org.hamcrest.Matchers;
 import org.joda.time.LocalDate;
 import org.junit.Before;
 import org.junit.Ignore;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
@@ -100,6 +102,8 @@ public class MappingMongoConverterUnitTests {
 	@Mock ApplicationContext context;
 	@Mock DbRefResolver resolver;
 
+	public @Rule ExpectedException exception = ExpectedException.none();
+
 	@Before
 	public void setUp() {
 
@@ -1826,6 +1830,29 @@ public class MappingMongoConverterUnitTests {
 		verify(mock, times(1)).getTarget();
 	}
 
+	/**
+	 * @see DATAMONGO-1034
+	 */
+	@Test
+	public void rejectsBasicDbListToBeConvertedIntoComplexType() {
+
+		BasicDBList inner = new BasicDBList();
+		inner.add("key");
+		inner.add("value");
+
+		BasicDBList outer = new BasicDBList();
+		outer.add(inner);
+		outer.add(inner);
+
+		BasicDBObject source = new BasicDBObject("attributes", outer);
+
+		exception.expect(MappingException.class);
+		exception.expectMessage(Item.class.getName());
+		exception.expectMessage(BasicDBList.class.getName());
+
+		converter.read(Item.class, source);
+	}
+
 	static class GenericType<T> {
 		T content;
 	}