Why are UTF-8 Strings Garbled When Using JDBC with MySQL?

Mistakes in Handling MySQL UTF-8 Strings in JDBC

Incorrectly handling UTF-8 strings in MySQL through the JDBC interface can lead to data corruption or display issues. This article examines a scenario where data inserted via JDBC appears garbled in the database.

The provided code snippet demonstrates a Java program that establishes a connection to a MySQL database and inserts UTF-8 text into a table. However, upon verifying the inserted data, the text is displayed incorrectly, with the expected characters replaced by question marks.

The problem lies in the character encoding settings within MySQL. By default, MySQL uses latin1 character set and collation, which is incompatible with UTF-8. To resolve this, the following steps are crucial:

1. Verify Character Encoding Settings

Execute the following SQL commands to view the current character encoding settings:

show variables like 'character%';
show variables like 'collation%';

The output should indicate that the character encoding is set to utf8 for both the server and the database.

2. Configure MySQL for UTF-8

If the encoding is not correct, modify it by updating the MySQL configuration file (my.cnf) by adding the following lines:

[mysqld]
character-set-server = utf8
character-set-filesystem = utf8

Alternatively, you can use MySQL Workbench to modify these settings visually.

3. Connect with Proper URL Parameters

When establishing the Java connection, include the following parameters in the JDBC URL:

jdbc:mysql://localhost:3306/myDatabase?useUnicode=true&characterEncoding=UTF-8

4. Remove Unnecessary Commands

Remove the following commands from your code:

query = "set character set utf8";
stat.execute(query);

These commands are not required when the connection parameters are correctly configured.

Expected Outcome

After applying these changes and restarting MySQL, the data should be stored and retrieved using JDBC correctly, displaying in the expected UTF-8 format.

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