1. Correspondence between database type and java type
Date-->java.sql.Date
Time-->java.sql.Time
TimeStamp-->java.sql.TimeStamp
2. Time type conversion
1. All contents in the java.sql package cannot appear in the domain object (domain), that is, the java.sql.Date type cannot be used
But!!! ResultSet.getDate() and PreparedStatement.setDate(int,Date) use java.sql.Date type
2.java.sql.Date Time TimeStamp----->java.util.Date
Just convert directly, because java.util.Date is their parent class
3.java.util.Date----->java.sql.Date Time TimeStamp
Convert the millisecond value under util to the long type of millisecond value, and use the millisecond value to create the millisecond value under sql