访问mysql数据库问题

我今天用navicat for mysql 时改表里的字段名时老出错，昨天也遇到过，我把管理用户里的权限全勾上后，就可以改了，今天却不行，我不小心吧localhost用户删了，这个用户是我电脑上的，还是navicat 上，重装navicat 也没这个用户。后面访问数据库报错
org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (null,  message from server: "Host 'localhost' is not allowed to connect to this MySQL server")
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1225)
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
at org.apache.commons.dbutils.QueryRunner.prepareConnection(QueryRunner.java:337)
at org.apache.commons.dbutils.QueryRunner.query(QueryRunner.java:485)
at org.apache.commons.dbutils.QueryRunner.query(QueryRunner.java:507)
at com.v512.jobedu.blog.DBOperator.getCategoryList(DBOperator.java:179)
at com.v512.jobedu.blog.BlogServlet.doPost(BlogServlet.java:38)
at com.v512.jobedu.blog.BlogServlet.doGet(BlogServlet.java:27)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.S