I have spring boot + mysql application and now it is working for use debezium to capture date change. but I wonder if it is possible to config the debezium for capturing the existing data
Yes, you'd use the snapshotting feature for that. It'll scan the existing tables (as per your whitelist/blacklist config) and create an event resembling the "insert" of all existing records.
Once the snapshot is completed, Debezium will switch into log reading mode, continueing to read the logs from the exact point in the log where the snapshot transaction was executed.