Optimize the usage of JacksonMongoSessionConverter to prevent duplicate MongoSession Document saves when a custom ObjectMapper is provided.#3185

Author: xiaoquanidea

spring-session-data-mongodb/src/main/java/org/springframework/session/data/mongo/JacksonMongoSessionConverter.java

@@ -16,11 +16,6 @@
 
 package org.springframework.session.data.mongo;
 
-import java.io.IOException;
-import java.util.Collections;
-import java.util.Date;
-import java.util.HashMap;
-
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -37,20 +32,25 @@
 import org.bson.Document;
 import org.bson.json.JsonMode;
 import org.bson.json.JsonWriterSettings;
-
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.lang.Nullable;
 import org.springframework.security.jackson2.SecurityJackson2Modules;
 import org.springframework.session.FindByIndexNameSessionRepository;
 import org.springframework.util.Assert;
 
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Date;
+import java.util.HashMap;
+
 /**
  * {@code AbstractMongoSessionConverter} implementation using Jackson.
  *
  * @author Jakub Kubrynski
  * @author Greg Turnquist
  * @author Michael Ruf
+ * @author TiQuan Hu
  * @since 1.2
  */
 public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter {
@@ -70,17 +70,27 @@ public JacksonMongoSessionConverter() {
 	}
 
 	public JacksonMongoSessionConverter(Iterable<Module> modules) {
-
 		this.objectMapper = buildObjectMapper();
 		this.objectMapper.registerModules(modules);
 	}
 
 	public JacksonMongoSessionConverter(ObjectMapper objectMapper) {
-
-		Assert.notNull(objectMapper, "ObjectMapper can NOT be null!");
+		Assert.notNull(objectMapper, "ObjectMapper can not be null!");
 		this.objectMapper = objectMapper;
 	}
 
+	public JacksonMongoSessionConverter(ObjectMapper objectMapper, boolean copyToUse) {
+		Assert.notNull(objectMapper, "ObjectMapper can not be null!");
+		if (!copyToUse) {
+			configureObjectMapper(objectMapper);
+			this.objectMapper = objectMapper;
+			return;
+		}
+		var objectMapperCopy = objectMapper.copy();
+		configureObjectMapper(objectMapperCopy);
+		this.objectMapper = objectMapperCopy;
+	}
+
 	@Nullable
 	protected Query getQueryForIndex(String indexName, Object indexValue) {
 
@@ -93,9 +103,12 @@ protected Query getQueryForIndex(String indexName, Object indexValue) {
 	}
 
 	private ObjectMapper buildObjectMapper() {
-
 		ObjectMapper objectMapper = new ObjectMapper();
+		this.configureObjectMapper(objectMapper);
+		return objectMapper;
+	}
 
+	private void configureObjectMapper(ObjectMapper objectMapper) {
 		// serialize fields instead of properties
 		objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.NONE);
 		objectMapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
@@ -108,8 +121,6 @@ private ObjectMapper buildObjectMapper() {
 		objectMapper.registerModules(SecurityJackson2Modules.getModules(getClass().getClassLoader()));
 		objectMapper.addMixIn(MongoSession.class, MongoSessionMixin.class);
 		objectMapper.addMixIn(HashMap.class, HashMapMixin.class);
-
-		return objectMapper;
 	}
 
 	@Override

spring-session-data-mongodb/src/main/java/org/springframework/session/data/mongo/MongoSession.java

@@ -16,30 +16,26 @@
 
 package org.springframework.session.data.mongo;
 
-import java.time.Duration;
-import java.time.Instant;
-import java.util.Date;
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Objects;
-import java.util.Set;
-import java.util.stream.Collectors;
-
 import org.springframework.lang.Nullable;
 import org.springframework.session.MapSession;
 import org.springframework.session.Session;
 import org.springframework.session.SessionIdGenerator;
 import org.springframework.session.UuidSessionIdGenerator;
 import org.springframework.util.Assert;
 
+import java.time.Duration;
+import java.time.Instant;
+import java.util.*;
+import java.util.stream.Collectors;
+
 /**
  * Session object providing additional information about the datetime of expiration.
  *
  * @author Jakub Kubrynski
  * @author Greg Turnquist
  * @since 1.2
  */
-class MongoSession implements Session {
+public class MongoSession implements Session {
 
 	/**
 	 * Mongo doesn't support {@literal dot} in field names. We replace it with a unicode