Incorrect string value: '\xAC\xED\x00\x05sr...' for column (3 replies)

I got this error which I need help to resovle.

java.sql.SQLException: Incorrect string value: '\xAC\xED\x00\x05sr...' for column 'subjectName' at row 1
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:975)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1114)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1062)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1383)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1047)

I have also checked the problem column Name : subjectName is in utf8mb4

What I have attempted so far:
-----------------------------
I have added my.cnf

[mysqld]
character-set-server=utf8mb4
collation-server=utf8mb4_unicode_ci

And re-start server but to no avail.

I am using MYSQL 8.0.12 in Windows 10, running a Maven web App in Java EE with CDI.

Eclipse Oxygen.

Please help.