怎么解決下呀，從dao層都沒有拿到數據？？測試login.do結果：debug調試結果：控制臺打印輸出：14-Aug-2017 15:43:49.005 警告 [http-nio-8080-exec-10] org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.handleHttpRequestMethodNotSupported Request method 'GET' not supported[15:44:48.815][DEBUG][org.mybatis.spring.SqlSessionUtils][http-nio-8080-exec-4] Creating a new SqlSession[15:44:48.851][DEBUG][org.mybatis.spring.SqlSessionUtils][http-nio-8080-exec-4] SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@34463302] was not registered for synchronization because synchronization is not active[15:44:51.497][DEBUG][o.m.s.t.SpringManagedTransaction][http-nio-8080-exec-4] JDBC Connection [jdbc:mysql://localhost:3306/mmall?characterEncoding=utf-8, UserName=root@localhost, MySQL-AB JDBC Driver] will not be managed by Spring[15:44:51.512][DEBUG][com.test.dao.UserMapper.checkUsername][http-nio-8080-exec-4] ==> ?Preparing: SELECT COUNT(1) FROM mmall_user WHERE username = ?[15:44:51.551][DEBUG][com.test.dao.UserMapper.checkUsername][http-nio-8080-exec-4] ==> Parameters: null[15:44:51.708][DEBUG][com.test.dao.UserMapper.checkUsername][http-nio-8080-exec-4] <== ? ? ?Total: 1[15:44:51.715][DEBUG][org.mybatis.spring.SqlSessionUtils][http-nio-8080-exec-4] Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@34463302]------ServiceImpl返回username=---------null------Controller返回username=---------null