Support generating JsonSchema for Polymorphic fields.

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>3.4.0-SNAPSHOT</version>
+	<version>3.4.0-GH-3870-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data MongoDB</name>

spring-data-mongodb-benchmarks/pom.xml

@@ -7,7 +7,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>3.4.0-SNAPSHOT</version>
+		<version>3.4.0-GH-3870-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb-distribution/pom.xml

@@ -14,7 +14,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>3.4.0-SNAPSHOT</version>
+		<version>3.4.0-GH-3870-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/pom.xml

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>3.4.0-SNAPSHOT</version>
+		<version>3.4.0-GH-3870-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

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

@@ -24,7 +24,6 @@
 import java.util.stream.Collectors;
 
 import org.bson.Document;
-
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
@@ -45,6 +44,7 @@
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -62,6 +62,7 @@ class MappingMongoJsonSchemaCreator implements MongoJsonSchemaCreator {
 	private final MongoConverter converter;
 	private final MappingContext<MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
 	private final Predicate<JsonSchemaPropertyContext> filter;
+	private final LinkedMultiValueMap<String, Class<?>> mergeProperties;
 
 	/**
 	 * Create a new instance of {@link MappingMongoJsonSchemaCreator}.
@@ -72,23 +73,51 @@ class MappingMongoJsonSchemaCreator implements MongoJsonSchemaCreator {
 	MappingMongoJsonSchemaCreator(MongoConverter converter) {
 
 		this(converter, (MappingContext<MongoPersistentEntity<?>, MongoPersistentProperty>) converter.getMappingContext(),
-				(property) -> true);
+				(property) -> true, new LinkedMultiValueMap<>());
 	}
 
 	@SuppressWarnings("unchecked")
 	MappingMongoJsonSchemaCreator(MongoConverter converter,
 			MappingContext<MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext,
-			Predicate<JsonSchemaPropertyContext> filter) {
+			Predicate<JsonSchemaPropertyContext> filter, LinkedMultiValueMap<String, Class<?>> mergeProperties) {
 
 		Assert.notNull(converter, "Converter must not be null!");
 		this.converter = converter;
 		this.mappingContext = mappingContext;
 		this.filter = filter;
+		this.mergeProperties = mergeProperties;
 	}
 
 	@Override
 	public MongoJsonSchemaCreator filter(Predicate<JsonSchemaPropertyContext> filter) {
-		return new MappingMongoJsonSchemaCreator(converter, mappingContext, filter);
+		return new MappingMongoJsonSchemaCreator(converter, mappingContext, filter, mergeProperties);
+	}
+
+	@Override
+	public PropertySpecifier specify(String path) {
+		return new PropertySpecifier() {
+			@Override
+			public MongoJsonSchemaCreator types(Class<?>... types) {
+				return specifyTypesFor(path, types);
+			}
+		};
+	}
+
+	/**
+	 * Specify additional types to be considered wehen rendering the schema for the given path.
+	 *
+	 * @param path path the path using {@literal dot '.'} notation.
+	 * @param types must not be {@literal null}.
+	 * @return new instance of {@link MongoJsonSchemaCreator}.
+	 * @since 3.4
+	 */
+	public MongoJsonSchemaCreator specifyTypesFor(String path, Class<?>... types) {
+
+		LinkedMultiValueMap<String, Class<?>> clone = mergeProperties.clone();
+		for (Class<?> type : types) {
+			clone.add(path, type);
+		}
+		return new MappingMongoJsonSchemaCreator(converter, mappingContext, filter, clone);
 	}
 
 	/*
@@ -135,9 +164,12 @@ private List<JsonSchemaProperty> computePropertiesForEntity(List<MongoPersistent
 
 			List<MongoPersistentProperty> currentPath = new ArrayList<>(path);
 
-			if (!filter.test(new PropertyContext(
-					currentPath.stream().map(PersistentProperty::getName).collect(Collectors.joining(".")), nested))) {
-				continue;
+			String stringPath = currentPath.stream().map(PersistentProperty::getName).collect(Collectors.joining("."));
+			stringPath = StringUtils.hasText(stringPath) ? (stringPath + "." + nested.getName()) : nested.getName();
+			if (!filter.test(new PropertyContext(stringPath, nested))) {
+				if (!mergeProperties.containsKey(stringPath)) {
+					continue;
+				}
 			}
 
 			if (path.contains(nested)) { // cycle guard
@@ -155,14 +187,34 @@ private List<JsonSchemaProperty> computePropertiesForEntity(List<MongoPersistent
 
 	private JsonSchemaProperty computeSchemaForProperty(List<MongoPersistentProperty> path) {
 
+		String stringPath = path.stream().map(MongoPersistentProperty::getName).collect(Collectors.joining("."));
 		MongoPersistentProperty property = CollectionUtils.lastElement(path);
 
 		boolean required = isRequiredProperty(property);
 		Class<?> rawTargetType = computeTargetType(property); // target type before conversion
 		Class<?> targetType = converter.getTypeMapper().getWriteTargetTypeFor(rawTargetType); // conversion target type
 
-		if (!isCollection(property) && property.isEntity() && ObjectUtils.nullSafeEquals(rawTargetType, targetType)) {
-			return createObjectSchemaPropertyForEntity(path, property, required);
+		if (!isCollection(property) && ObjectUtils.nullSafeEquals(rawTargetType, targetType)) {
+			if (property.isEntity() || mergeProperties.containsKey(stringPath)) {
+				List<JsonSchemaProperty> targetProperties = new ArrayList<>();
+
+				if (property.isEntity()) {
+					targetProperties.add(createObjectSchemaPropertyForEntity(path, property, required));
+				}
+				if (mergeProperties.containsKey(stringPath)) {
+					for (Class<?> theType : mergeProperties.get(stringPath)) {
+
+						ObjectJsonSchemaProperty target = JsonSchemaProperty.object(property.getName());
+						List<JsonSchemaProperty> nestedProperties = computePropertiesForEntity(path,
+								mappingContext.getRequiredPersistentEntity(theType));
+
+						targetProperties.add(createPotentiallyRequiredSchemaProperty(
+								target.properties(nestedProperties.toArray(new JsonSchemaProperty[0])), required));
+					}
+				}
+				return targetProperties.size() == 1 ? targetProperties.iterator().next()
+						: JsonSchemaProperty.combined(targetProperties);
+			}
 		}
 
 		String fieldName = computePropertyFieldName(property);

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

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mongodb.core;
 
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.function.Predicate;
@@ -62,7 +63,6 @@
  * {@link org.springframework.data.annotation.Id _id} properties using types that can be converted into
  * {@link org.bson.types.ObjectId} like {@link String} will be mapped to {@code type : 'object'} unless there is more
  * specific information available via the {@link org.springframework.data.mongodb.core.mapping.MongoId} annotation.
-
  * {@link Encrypted} properties will contain {@literal encrypt} information.
  *
  * @author Christoph Strobl
@@ -78,6 +78,20 @@ public interface MongoJsonSchemaCreator {
 	 */
 	MongoJsonSchema createSchemaFor(Class<?> type);
 
+	/**
+	 * Create a combined {@link MongoJsonSchema} out of the individual schemas of the given types by combining their
+	 * properties into one large {@link MongoJsonSchema schema}.
+	 * 
+	 * @param types must not be {@literal null} nor contain {@literal null}.
+	 * @return new instance of {@link MongoJsonSchema}.
+	 * @since 3.4
+	 */
+	default MongoJsonSchema combineSchemaFor(Class<?>... types) {
+
+		MongoJsonSchema[] schemas = Arrays.stream(types).map(this::createSchemaFor).toArray(MongoJsonSchema[]::new);
+		return MongoJsonSchema.combined(schemas);
+	}
+
 	/**
 	 * Filter matching {@link JsonSchemaProperty properties}.
 	 *
@@ -87,6 +101,15 @@ public interface MongoJsonSchemaCreator {
 	 */
 	MongoJsonSchemaCreator filter(Predicate<JsonSchemaPropertyContext> filter);
 
+	/**
+	 * Entry point to specify additional behavior for a given path.
+	 *
+	 * @param path the path using {@literal dot '.'} notation.
+	 * @return new instance of {@link PropertySpecifier}.
+	 * @since 3.4
+	 */
+	PropertySpecifier specify(String path);
+
 	/**
 	 * The context in which a specific {@link #getProperty()} is encountered during schema creation.
 	 * 
@@ -209,4 +232,20 @@ static MongoJsonSchemaCreator create() {
 
 		return create(converter);
 	}
+
+	/**
+	 * @since 3.4
+	 * @author Christoph Strobl
+	 * @since 3.4
+	 */
+	interface PropertySpecifier {
+
+		/**
+		 * Set additional type parameters for polymorphic ones.
+		 *
+		 * @param types must not be {@literal null}.
+		 * @return the source
+		 */
+		MongoJsonSchemaCreator types(Class<?>... types);
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/schema/CombinedJsonSchema.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.schema;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.function.BiFunction;
+
+import org.bson.Document;
+
+/**
+ * {@link MongoJsonSchema} implementation that is capable of combining properties of different schemas into one.
+ *
+ * @author Christoph Strobl
+ * @since 3.4
+ */
+class CombinedJsonSchema implements MongoJsonSchema {
+
+	private final List<MongoJsonSchema> schemaList;
+	private final BiFunction<Map<String, Object>, Map<String, Object>, Document> mergeFunction;
+
+	CombinedJsonSchema(List<MongoJsonSchema> schemaList, ConflictResolutionFunction conflictResolutionFunction) {
+		this(schemaList, new TypeUnifyingMergeFunction(conflictResolutionFunction));
+	}
+
+	CombinedJsonSchema(List<MongoJsonSchema> schemaList,
+			BiFunction<Map<String, Object>, Map<String, Object>, Document> mergeFunction) {
+
+		this.schemaList = new ArrayList<>(schemaList);
+		this.mergeFunction = mergeFunction;
+	}
+
+	@Override
+	public MongoJsonSchema combineWith(Collection<MongoJsonSchema> sources) {
+
+		schemaList.addAll(sources);
+		return this;
+	}
+
+	@Override
+	public Document schemaDocument() {
+
+		Document targetSchema = new Document();
+		for (MongoJsonSchema schema : schemaList) {
+			targetSchema = mergeFunction.apply(targetSchema, schema.schemaDocument());
+		}
+
+		return targetSchema;
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/schema/CombinedJsonSchemaProperty.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.schema;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.BiFunction;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.schema.MongoJsonSchema.ConflictResolutionFunction;
+
+/**
+ * {@link JsonSchemaProperty} implementation that is capable of combining multiple properties with different values into
+ * a single one.
+ *
+ * @author Christoph Strobl
+ * @since 3.4
+ */
+class CombinedJsonSchemaProperty implements JsonSchemaProperty {
+
+	private final Iterable<JsonSchemaProperty> properties;
+	private final BiFunction<Map<String, Object>, Map<String, Object>, Document> mergeFunction;
+
+	CombinedJsonSchemaProperty(Iterable<JsonSchemaProperty> properties) {
+		this(properties, (k, a, b) -> {
+			throw new IllegalStateException(
+					String.format("Error resolving conflict for %s. No conflict resolution function defined.", k));
+		});
+	}
+
+	CombinedJsonSchemaProperty(Iterable<JsonSchemaProperty> properties,
+			ConflictResolutionFunction conflictResolutionFunction) {
+		this(properties, new TypeUnifyingMergeFunction(conflictResolutionFunction));
+	}
+
+	CombinedJsonSchemaProperty(Iterable<JsonSchemaProperty> properties,
+			BiFunction<Map<String, Object>, Map<String, Object>, Document> mergeFunction) {
+
+		this.properties = properties;
+		this.mergeFunction = mergeFunction;
+	}
+
+	@Override
+	public Set<Type> getTypes() {
+		return Collections.emptySet();
+	}
+
+	@Override
+	public Document toDocument() {
+
+		Document document = new Document();
+
+		for (JsonSchemaProperty property : properties) {
+			document = mergeFunction.apply(document, property.toDocument());
+		}
+		return document;
+	}
+
+	@Override
+	public String getIdentifier() {
+		return properties.iterator().next().getIdentifier();
+	}
+}