https://www.cnblogs.com/lowwen/p/5645242.html

问题描述：
java.sql.SQLException: Incorrect string value: '\xF0\x9F\x90\xBB' for column 'nickName' at row 1
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1094)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4226)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4158)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2615)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2776)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2840)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1302)
at sun.reflect.GeneratedMethodAccessor49.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:55)
at com.sun.proxy.$Proxy58.execute(Unknown Source)
at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:41)
at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:66)
at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:45)
at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:100)
at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:75)
解决方法：
1.建表的时候添加如下限制：ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
2.在my.cnf上修改如下：
------------------my.cnf------------------------------------------------------

For advice on how to change settings please see

http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html

[client]
default-character-set=utf8mb4
[mysql]
default-character-set = utf8mb4

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
log-error=/var/log/mysqld.log
long_query_time=3

[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
init_connect='SET NAMES utf8mb4'

log-slow-queries= /usr/local/mysql/log/slowquery.log

重启mysql服务，service mysql stop； service mysql start；问题解决。
造成这个问题的原因（网上找的）：
mysql中规定utf8字符的最大字节数是3，但是某些unicode字符转成utf8编码之后有4个字节，导致出错。