Today, I used java to connect to Oracle 12c for the first time. I encountered various problems. In order to facilitate subsequent inquiries, the problem records and solutions are summarized as follows.
ORA-28040: No matching authentication protocol
Need to be in...\product\12.1.0\dbhome_1\NETWORK\ADMIN\sqlnet.ora
add to file
SQLNET.ALLOWED_LOGON_VERSION=8
ORA-12505： TNS:listener does not currently know of SID given in connect descriptor
The SID should be an existing id. When java connects to Oracle 12c, it cannot recognize the SID in the incorrect format, and it should be handled as the following problem.
ORA-01017: invalid username/password; logon denied
In pdb mode, the connection string should be in this format
jdbc:oracle:thin:@localhost:1521/pdborcl
Similar to the colon behind, or adding // before locahost, it cannot be used normally.