Why are my Cyrillic strings appearing as \"????????\" in my MySQL database despite setting `characterEncoding=utf-8` in my JDBC connection?

How to Encode UTF-8 Strings Correctly for MySQL Using JDBC

Introduction

When working with MySQL through JDBC, it's essential to understand how to encode UTF-8 strings properly to ensure data integrity and avoid character corruption. This article addresses the common issue of incorrect UTF-8 encoding, leading to garbled text in MySQL.

Problem Statement

Rows inserted into a MySQL table using JDBC were displayed with incorrect characters, showing "????????" instead of the intended Cyrillic text. This problem persisted despite setting "characterEncoding=utf-8" in the connection string and executing SQL statements to set the character set.

MySQL Configuration

To resolve the issue, it's crucial to verify the MySQL configuration settings. Execute the following commands to check the character encoding and collation settings:

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

JDBC Connection Configuration

Ensure that the JDBC connection string includes the correct character encoding and Unicode settings:

con = DriverManager.getConnection("jdbc:mysql://localhost:3306/myDatabase?useUnicode=true&characterEncoding=UTF-8","user","passwd");

SQL Statements for Character Set Management

It's generally not necessary to execute SQL statements to set the character set and encoding explicitly. By default, MySQL uses the settings configured through my.cnf or my.ini. However, in some cases, you may need to execute the following statements:

<code class="sql">SET NAMES 'utf8';
SET CHARACTER SET 'utf8';</code>

Database Table Definition

Ensure that the database table is defined with the correct character set and encoding:

<code class="sql">CREATE TABLE clt (
  id bigint NOT NULL,
  text varchar(50) NOT NULL
) DEFAULT CHARACTER SET utf8;</code>

Stripping Unnecessary SQL Statements

The example code provided unnecessarily executes SQL statements to set the character set. Removing the following statements resolves the issue:

<code class="sql">query = "set character set utf8";
stat.execute(query);</code>

Database-Side Configuration

As a final step, verify that the database-side configuration matches the JDBC and code settings. This includes modifying my.cnf or my.ini to set the appropriate character-set-server and character-set-filesystem parameters.

By following these guidelines, you can ensure accurate UTF-8 string handling in your MySQL database through JDBC, preventing garbled text and maintaining data integrity.

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