WebSphere Application Server version 9 supports both the JPA 2.1 and JPA 2.0 specification levels.
Please refer to the following link for details:
https://www.ibm.com/support/knowledgecenter/SSEQTP_9.0.5/com.ibm.websphere.base.doc/ae/tejb_idmod_jpaspec.html
https://www.ibm.com/support/knowledgecenter/SSEQTP_9.0.5/com.ibm.websphere.base.doc/ae/tejb_configpp.html
https://www.ibm.com/support/knowledgecenter/SSEQTP_9.0.5/com.ibm.websphere.base.doc/ae/covr_javaee7.html
Regarding compatibility with Hibernate 5.3.7 please take a look at the following links:
https://hibernate.org/orm/releases/5.3/
https://www.ibm.com/software/reports/compatibility/clarity-reports/report/html/softwareReqsForProduct?deliverableId=516A7D50201B11E9AEAFE0FEBCE2D22F&osPlatforms=AIX|HP|IBM%20i|Linux|Solaris|Windows&duComponentIds=S000&mandatoryCapIds=13|132&optionalCapIds=341|9|39|8|132|20|223|26|40#sw-4
https://www.oracle.com/java/technologies/javaee/javaeetechnologies.html#javaee7
https://www.oracle.com/java/technologies/javaee/javaeetechnologies.html#javaee7
Traditional WebSphere 9.0 supports Java EE 7 which is JPA 2.1.
Hibernate 5.3 is compatible with JPA 2.2.
Running with Hibernate that supports JPA 2.2 is not recommended and will most likely result in errors.
#Support#SupportMigration#WebSphereApplicationServer(WAS)