DATAMONGO-2200 - Polishing.

Tweak Javadoc. Simplify Fields creation from Stream. Remove final modifier from private static method. Iterate with loop over PersistentEntity.

Original pull request: #748.

Author: mp911de

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOperationContext.java

@@ -18,10 +18,9 @@
 import java.beans.PropertyDescriptor;
 import java.lang.reflect.Method;
 import java.util.Arrays;
-import java.util.List;
-import java.util.stream.Collectors;
 
 import org.bson.Document;
+
 import org.springframework.beans.BeanUtils;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
 import org.springframework.lang.Nullable;
@@ -77,17 +76,20 @@ default Document getMappedObject(Document document) {
 	FieldReference getReference(String name);
 
 	/**
-	 * Returns the {@link Fields} exposed by the type. May be a {@literal class} or an {@literal interface}.
+	 * Returns the {@link Fields} exposed by the type. May be a {@literal class} or an {@literal interface}. The default
+	 * implementation uses {@link BeanUtils#getPropertyDescriptors(Class) property descriptors} discover fields from a
+	 * {@link Class}.
 	 *
 	 * @param type must not be {@literal null}.
 	 * @return never {@literal null}.
 	 * @since 2.2
+	 * @see BeanUtils#getPropertyDescriptor(Class, String)
 	 */
 	default Fields getFields(Class<?> type) {
 
 		Assert.notNull(type, "Type must not be null!");
 
-		List<String> fields = Arrays.stream(BeanUtils.getPropertyDescriptors(type)) //
+		return Fields.fields(Arrays.stream(BeanUtils.getPropertyDescriptors(type)) //
 				.filter(it -> { // object and default methods
 					Method method = it.getReadMethod();
 					if (method == null) {
@@ -99,8 +101,6 @@ default Fields getFields(Class<?> type) {
 					return !method.isDefault();
 				}) //
 				.map(PropertyDescriptor::getName) //
-				.collect(Collectors.toList());
-
-		return Fields.fields(fields.toArray(new String[0]));
+				.toArray(String[]::new));
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Fields.java

@@ -112,7 +112,7 @@ private Fields(List<Field> fields) {
 		this.fields = verify(fields);
 	}
 
-	private static final List<Field> verify(List<Field> fields) {
+	private static List<Field> verify(List<Field> fields) {
 
 		Map<String, Field> reference = new HashMap<String, Field>();
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ProjectionOperation.java

@@ -22,6 +22,7 @@
 import java.util.List;
 
 import org.bson.Document;
+
 import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond;
 import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
@@ -30,7 +31,6 @@
 import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.util.ReflectionUtils;
 
 /**
  * Encapsulates the aggregation framework {@code $project}-operation.
@@ -1739,7 +1739,7 @@ public Document toDocument(AggregationOperationContext context) {
 			Document projections = new Document();
 
 			Fields fields = context.getFields(type);
-			fields.asList().forEach(it -> projections.append(it.getName(), 1));
+			fields.forEach(it -> projections.append(it.getName(), 1));
 			return context.getMappedObject(projections, type);
 		}
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/TypeBasedAggregationOperationContext.java

@@ -21,8 +21,8 @@
 import java.util.List;
 
 import org.bson.Document;
+
 import org.springframework.data.mapping.PersistentPropertyPath;
-import org.springframework.data.mapping.SimplePropertyHandler;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
@@ -111,14 +111,21 @@ public FieldReference getReference(String name) {
 	@Override
 	public Fields getFields(Class<?> type) {
 
+		Assert.notNull(type, "Type must not be null!");
+
 		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(type);
+
 		if (entity == null) {
 			return AggregationOperationContext.super.getFields(type);
 		}
 
 		List<String> fields = new ArrayList<>();
-		entity.doWithProperties((SimplePropertyHandler) it -> fields.add(it.getName()));
-		return Fields.fields(fields.toArray(new String[fields.size()]));
+
+		for (MongoPersistentProperty property : entity) {
+			fields.add(property.getName());
+		}
+
+		return Fields.fields(fields.toArray(new String[0]));
 	}
 
 	private FieldReference getReferenceFor(Field field) {