后端写sql语句，可以正常显示中文，但在前端页面中新增/编辑的中文内容，还是显示？？？ idea的setting里，encode全改了，数据库也改成utf8mb4,实在不知道问题在哪里、。 之前一个courseimooc项目，setting里encode还有几个是GBK，结果在前端新增或编辑后也能正常显示，这个项目里就是一直问号 如下日志中的黑体字，后端输入值是中文“教程”，输出以后变成“??”

20.282 DEBUG c.s.w.m.EbookMapper.insert :137 http-nio-8880-exec-5 ==> Preparing: insert into ebook (id, name, category1_id, category2_id, description, cover, doc_count, view_count, vote_count ) values (?, ?, ?, ?, ?, ?, ?, ?, ? )
20.284 DEBUG c.s.w.m.EbookMapper.insert :137 http-nio-8880-exec-5 > Parameters: 43693743668334592(Long), 教程(String), 1(Long), 1(Long), 教程(String), null, null, null, null
20.297 DEBUG c.s.w.m.EbookMapper.insert :137 http-nio-8880-exec-5 < Updates: 1

20.338 DEBUG c.s.w.m.E.selectByExample :137 http-nio-8880-exec-6 > Preparing: select id, name, category1_id, category2_id, description, cover, doc_count, view_count, vote_count from ebook LIMIT ?
20.338 DEBUG c.s.w.m.E.selectByExample :137 http-nio-8880-exec-6 > Parameters: 10(Integer)
20.339 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 < Columns: id, name, category1_id, category2_id, description, cover, doc_count, view_count, vote_count
20.340 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 < Row: 1, Spring Boot 入门教程, null, null, 零基础入门 Java 开发，企业级应用开发最佳首选框架, null, null, null, null
20.341 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 <== Row: 2, Vue 入门教程, null, null, 零基础入门 Vue 开发，企业级应用开发最佳首选框架, null, null, null, null
20.341 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 <== Row: 3, Python 入门教程, null, null, 零基础入门 Python 开发，企业级应用开发最佳首选框架, null, null, null, null
20.341 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 <== Row: 4, Mysql 入门教程, null, null, 零基础入门 Mysql 开发，企业级应用开发最佳首选框架, null, null, null, null
20.342 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 <== Row: 5, Oracle 入门教程, null, null, 零基础入门 Oracle 开发，企业级应用开发最佳首选框架, null, null, null, null
20.342 TRACE c.s.w.m.E.selectByExample :143 http-nio-8880-exec-6 <== Row: 43693743668334592, ??, 1, 1, ??, null, null, null, null
20.342 DEBUG c.s.w.m.E.selectByExample :137 http-nio-8880-exec-6 <== Total: 6