linux环境下的yum默认mysql版本是5.1的，由于项目需要保存表情等4个字节的数据，版本受限，需要升级到5.6版本支持utf8mb4格式的编码。
升级过程大概就是备份数据库，完全卸载旧版本，重新安装5.6版本，原先5.1版本下的数据库需要根据自己情况调整设置
修改数据库编码格式
例如：
ALTER DATABASE Test CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
修改表的编码格式
例如：
ALTER TABLE TABLE_NAME CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
测试提交emoji表情，仍然返回不能保存这个字符
java.sql.SQLException: Incorrect string value: ‘\xF0\x9F\x92\x94’ for column ‘name’ at row 1
SHOW VARIABLES WHERE Variable_name LIKE ‘character_set_%‘ OR Variable_name LIKE ‘collation%‘;
| Variable_name | Value |
|---|---|
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| collation_connection | utf8_unicode_ci |
| collation_database | utf8_unicode_ci |
| collation_server | utf8_unicode_ci |
发现数据库的系统变量仍然是utf8编码格式的
以下几个一定要设置成utf8mb4格式
| 系统变量 | 描述 |
|---|---|
| character_set_client | (客户端来源数据使用的字符集) |
| character_set_connection | (连接层字符集) |
| character_set_database | (当前选中数据库的默认字符集) |
| character_set_results | (查询结果字符集) |
| character_set_server | (默认的内部操作字符集) |
数据库连接参数中:
characterEncoding=utf8会被自动识别为utf8mb4，也可以不加这个参数，会自动检测。
而autoReconnect=true是必须加上的。
下面的这个是mysql的配置文件，尤为重要，如果不指定启动的编码格式，还是会默认安装utf8格式启动，就算数据库和表字段都设置成utf8mb4编码格式依然会不能保存4个字节的数据
# For advice on how to change settings please see # http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html # *** DO NOT EDIT THIS FILE. It‘s a template which will be copied to the # *** default location during install, and will be replaced if you # *** upgrade to a newer version of MySQL. [mysqld] # Remove leading # and set to the amount of RAM for the most important data # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%. # innodb_buffer_pool_size = 128M # Remove leading # to turn on a very important data integrity option: logging # changes to the binary log between backups. # log_bin # These are commonly set, remove the # and set as required. # basedir = ..... # datadir = ..... # port = ..... # server_id = ..... # socket = ..... # Remove leading # to set options mainly useful for reporting servers. # The server defaults are faster for transactions and fast SELECTs. # Adjust sizes as needed, experiment to find the optimal values. # join_buffer_size = 128M # sort_buffer_size = 2M # read_rnd_buffer_size = 2M sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES [client] default-character-set = utf8mb4 [mysql] default-character-set = utf8mb4 [mysqld] character-set-client-handshake = FALSE character-set-server = utf8mb4 collation-server = utf8mb4_unicode_ci init_connect=‘SET NAMES utf8mb4‘
如果你已经启动mysql了，使用这个配置重启服务即可
service mysqld stop// 关闭服务
service mysqld start// 开启服务
重启完成后我们再次查看系统变量，输出如下
| Variable_name | Value |
|---|---|
| character_set_client | utf8mb4 |
| character_set_connection | utf8mb4 |
| character_set_database | utf8mb4 |
| character_set_filesystem | binary |
| character_set_results | utf8mb4 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| collation_connection | utf8mb4_unicode_ci |
| collation_database | utf8mb4_unicode_ci |
| collation_server | utf8mb4_unicode_ci |
再次测试自己的接口，保存成功
原文：https://www.cnblogs.com/MrSong97/p/10500130.html