Set expireAt properly to support TTL indexing.

src/main/java/org/springframework/session/data/mongo/JacksonMongoSessionConverter.java

@@ -17,6 +17,7 @@ package org.springframework.session.data.mongo;
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.Date;
 import java.util.HashMap;
 
 import org.apache.commons.logging.Log;
@@ -46,6 +47,7 @@ import com.mongodb.util.JSON;
  *
  * @author Jakub Kubrynski
  * @author Greg Turnquist
+ * @author Michael Ruf
  * @since 1.2
  */
 public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter {
@@ -54,6 +56,7 @@ public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter
 
 	private static final String ATTRS_FIELD_NAME = "attrs.";
 	private static final String PRINCIPAL_FIELD_NAME = "principal";
+	private static final String EXPIRE_AT_FIELD_NAME = "expireAt";
 
 	private final ObjectMapper objectMapper;
 
@@ -108,6 +111,7 @@ public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter
 
 		try {
 			DBObject dbSession = (DBObject) JSON.parse(this.objectMapper.writeValueAsString(source));
+			dbSession.put(EXPIRE_AT_FIELD_NAME, source.getExpireAt());
 			dbSession.put(PRINCIPAL_FIELD_NAME, extractPrincipal(source));
 			return dbSession;
 		} catch (JsonProcessingException e) {
@@ -119,10 +123,14 @@ public class JacksonMongoSessionConverter extends AbstractMongoSessionConverter
 	@Nullable
 	protected MongoSession convert(Document source) {
 
+		Date expireAt = source.getDate(EXPIRE_AT_FIELD_NAME);
+		source.remove(EXPIRE_AT_FIELD_NAME);
 		String json = source.toJson(JsonWriterSettings.builder().outputMode(JsonMode.RELAXED).build());
 
 		try {
-			return this.objectMapper.readValue(json, MongoSession.class);
+			MongoSession mongoSession = this.objectMapper.readValue(json, MongoSession.class);
+			mongoSession.setExpireAt(expireAt);
+			return mongoSession;
 		} catch (IOException e) {
 			LOG.error("Error during Mongo Session deserialization", e);
 			return null;

src/test/java/org/springframework/session/data/mongo/JacksonMongoSessionConverterTest.java

@@ -18,7 +18,11 @@ package org.springframework.session.data.mongo;
 import static org.assertj.core.api.AssertionsForClassTypes.*;
 
 import java.lang.reflect.Field;
+import java.util.Date;
+import java.util.HashMap;
 
+import org.bson.Document;
+import org.bson.types.ObjectId;
 import org.junit.Test;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.util.ReflectionUtils;
@@ -85,4 +89,37 @@ public class JacksonMongoSessionConverterTest extends AbstractMongoSessionConver
 
 		new JacksonMongoSessionConverter((ObjectMapper) null);
 	}
+
+	@Test
+	public void shouldSaveExpireAtAsDate() {
+
+		//given
+		MongoSession session = new MongoSession();
+
+		//when
+		DBObject convert = this.mongoSessionConverter.convert(session);
+
+		//then
+		assertThat(convert.get("expireAt")).isInstanceOf(Date.class);
+		assertThat(convert.get("expireAt")).isEqualTo(session.getExpireAt());
+	}
+
+	@Test
+	public void shouldLoadExpireAtFromDocument() {
+
+		// given
+		Date now = new Date();
+		HashMap data = new HashMap();
+		data.put("expireAt", now);
+		data.put("@class", MongoSession.class.getName());
+		data.put("_id", new ObjectId().toString());
+		Document document = new Document(data);
+
+		// when
+		MongoSession convertedSession = this.mongoSessionConverter.convert(document);
+
+		// then
+		assertThat(convertedSession.getExpireAt()).isEqualTo(now);
+	}
+
 }