debugging json

1. https://notes.georgboe.com/post/debug-http-400-errors-in-spring-mvc/
2. https://stackoverflow.com/questions/7952154/spring-resttemplate-how-to-enable-full-debugging-logging-of-requests-responses
3. https://pubs.vmware.com/vfabric51/index.jsp?topic=/com.vmware.vfabric.vas.1.0/vas/api-vfabric-docs.html
4. https://stackoverflow.com/questions/38974428/jquery-alerts-undefined-on-error-instead-of-java-spring-exception-details
5.