com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'admin' for key 'UK

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'admin' for key 'UK_dgxl7aijrr4hq8314exhw407s'

严重: Servlet.service() for servlet [spring-mvc] in context with path [/learn] threw exception [Request processing failed; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'admin' for key 'UK_dgxl7aijrr4hq8314exhw407s'
   at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
   at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
   at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

1、MySQLIntegrityConstraintViolationException是指外键出错了

2、Duplicate entry 'admin'for key 'PRIMARY'是指重复了我的用户名设为唯一了