mysql - java.sql.SQLException: Incorrect string value: 'xF0x9Fx91xBDxF0x9F...'

Question

I have the following string value: "walmart obama ????"

I am using MySQL and Java.

I am getting the following exception: `java.sql.SQLException: Incorrect string value: 'xF0x9Fx91xBDxF0x9F...'

Here is the variable I am trying to insert into:

var1 varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL`

My Java code that is trying to insert "walmart obama ????" is a preparedStatement. So I am using the setString() method.

It looks like the problem is the encoding of the values ????. How can I fix this? Previously I was using Derby SQL and the values ???? just ended up being two sqaures (I think this is the representation of the null character)

All help is greatly appreciated!

Answer 1

What you have is EXTRATERRESTRIAL ALIEN (U+1F47D) and BROKEN HEART (U+1F494) which are not in the basic multilingual plane. They cannot be even represented in java as one char, "????".length() == 4. They are definitely not null characters and one will see squares if you are not using fonts that support them.

MySQL's utf8 only supports basic multilingual plane, and you need to use utf8mb4 instead:

For a supplementary character, utf8 cannot store the character at all, while utf8mb4 requires four bytes to store it. Since utf8 cannot store the character at all, you do not have any supplementary characters in utf8 columns and you need not worry about converting characters or losing data when upgrading utf8 data from older versions of MySQL.

So to support these characters, your MySQL needs to be 5.5+ and you need to use utf8mb4 everywhere. Connection encoding needs to be utf8mb4, character set needs to be utf8mb4 and collaction needs to be utf8mb4. For java it's still just "utf-8", but MySQL needs a distinction.

I don't know what driver you are using but a driver agnostic way to set connection charset is to send the query:

SET NAMES 'utf8mb4'

Right after making the connection.

See also this for Connector/J:

14.14: How can I use 4-byte UTF8, utf8mb4 with Connector/J?

To use 4-byte UTF8 with Connector/J configure the MySQL server with character_set_server=utf8mb4. Connector/J will then use that setting as long as characterEncoding has not been set in the connection string. This is equivalent to autodetection of the character set.

Adjust your columns and database as well:

var1 varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL

Again, your MySQL version needs to be relatively up-to-date for utf8mb4 support.