“Incorrect string value” when trying to insert UTF-8 into MySQL via JDBC?

Question

This is how my connection is set:
Connection conn = DriverManager.getConnection(url + dbName + \"?useUnicode=true&characterEncoding=utf-8\", userName, password

Answer 1

Got the same problem, to save the data with utf8mb4 needs to make sure:

1. character_set_client, character_set_connection, character_set_results are utf8mb4: character_set_client and character_set_connection indicate the character set in which statements are sent by the client, character_set_results indicates the character set in which the server returns query results to the client.
   See charset-connection.

2. the table and column encoding is utf8mb4

For JDBC, there are two solutions:

Solution 1 (need to restart MySQL):

1. modify my.cnf like the following and restart MySQL:

   [mysql]
   default-character-set=utf8mb4
   
   [mysqld]
   character-set-server=utf8mb4
   collation-server=utf8mb4_unicode_ci
   

this can make sure the database and character_set_client, character_set_connection, character_set_results are utf8mb4 by default.

2. restart MySQL

3. change the table and column encoding to utf8mb4

4. STOP specifying characterEncoding=UTF-8 and characterSetResults=UTF-8 in the jdbc connector,cause this will override character_set_client, character_set_connection, character_set_results to utf8

Solution two (don't need to restart MySQL):

1. change the table and column encoding to utf8mb4

2. specifying characterEncoding=UTF-8 in the jdbc connector,cause the jdbc connector doesn't suport utf8mb4.

3. write your sql statment like this (need to add allowMultiQueries=true to jdbc connector):

   'SET NAMES utf8mb4;INSERT INTO Mytable ...';
   

this will make sure each connection to the server, character_set_client,character_set_connection,character_set_results are utf8mb4.
Also see charset-connection.