"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);

And I'm getting the following error when tyring to add a row to a table:
Incorrect string value: '\xF0\x90\x8D\x83\xF0\x90...' for column 'content' at row 1

I'm inserting thousands of records, and I always get this error when the text contains \xF0 (i.e. the the incorrect string value always starts with \xF0).

The column's collation is utf8_general_ci.

What could be the problem?

Answer 1

MySQL's utf8 permits only the Unicode characters that can be represented with 3 bytes in UTF-8. Here you have a character that needs 4 bytes: \xF0\x90\x8D\x83 (U+10343 GOTHIC LETTER SAUIL).

If you have MySQL 5.5 or later you can change the column encoding from utf8 to utf8mb4. This encoding allows storage of characters that occupy 4 bytes in UTF-8.

You may also have to set the server property character_set_server to utf8mb4 in the MySQL configuration file. It seems that Connector/J defaults to 3-byte Unicode otherwise:

For example, to use 4-byte UTF-8 character sets with Connector/J, configure the MySQL server with character_set_server=utf8mb4, and leave characterEncoding out of the Connector/J connection string. Connector/J will then autodetect the UTF-8 setting.

Answer 2

The strings that contain \xF0 are simply characters encoded as multiple bytes using UTF-8.

Although your collation is set to utf8_general_ci, I suspect that the character encoding of the database, table or even column may be different. They are independent settings. Try:

ALTER TABLE database.table MODIFY COLUMN col VARCHAR(255)       CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL; 

Substitute whatever your actual data type is for VARCHAR(255)