Unknown initial character set index '255' received from server

Question

Some further investigation showed that the issue was exactly in changes which were done in MySQL v.8.0:

Character Set Support

Important Change: The default character set has changed from latin1 to utf8mb4. These system variables are affected:

The default value of the character_set_server and character_set_database system variables has changed from latin1 to utf8mb4.

The default value of the collation_server and collation_database system variables has changed from latin1_swedish_ci to utf8mb4_0900_ai_ci.

All these change were already processed in new version of mysql-connector-java and there is no need to configure your MySQL. So change from 5.1.6 to 5.1.44 fix the issue:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.44</version>
</dependency>

User below URL, It works for me.

url=jdbc:mysql://localhost:3306/hybrisdb?characterEncoding=latin1&useConfigs=maxPerformance

This Works for me!

 <property name="JDBC.ConnectionURL"  value="jdbc:mysql://localhost:3306/empdemo?characterEncoding=utf8"></property>

This below change worked to me

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.44</version>
    </dependency>

for this connection

    @Bean
@Profile("dev")
public DataSource dataSourceDev() {
    DriverManagerDataSource dataSource = new DriverManagerDataSource();
    dataSource.setUsername("root");
    dataSource.setPassword("password");
    dataSource.setUrl("jdbc:mysql://localhost:3306/<yourdatabasehere>");
    dataSource.setDriverClassName("com.mysql.jdbc.Driver");
    return dataSource;
}

This works for me and you can try this too :)

url="jdbc:mysql://localhost:3306/dbname?characterEncoding=utf8"

Was facing the same issue.. So I updated the connector version(8.0.18) and it was resolved.

What helped for me was appending this to my URL:

useUnicode=true&character_set_server=utf8mb4&useLegacyDatetimeCode=false

This completely fixed the issue.