JDBC is corrupting special characters from MySQL

Question

I have a MySql 5.7.20 database table called deliveries with a column called message which is of type blob.

I want this to be able to support special characters like emojis. I can insert and view a row with an emoji:

I know want to read this out with java. My code is:

public class JavaMysqlSelectExample
{

    public static void main(String[] args)
    {
        try
        {
            // create our mysql database connection
            String myDriver = "com.mysql.jdbc.Driver";
            String myUrl = "jdbc:mysql://localhost/products?useUnicode=true&characterEncoding=UTF-8";
            Class.forName(myDriver);
            Connection conn = DriverManager.getConnection(myUrl, "mark", "hht6yyt6yyt6");

            // our SQL SELECT query.
            // if you only need a few columns, specify them by name instead of using "*"
            String query = "SELECT SUBSTRING(message,1,2500) as message FROM deliveries where id = 9";

            // create the java statement
            Statement st = conn.createStatement();

            // execute the query, and get a java resultset
            ResultSet rs = st.executeQuery(query);

            // iterate through the java resultset
            while (rs.next())
            {
                String message = rs.getString("message");

                // print the results
                System.out.format("%s", message);
            }
            st.close();
        }
        catch (Exception e)
        {
            System.err.println("Got an exception! ");
            System.err.println(e.getMessage());
        }
    }
}

My POM file is:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>test</groupId>
    <artifactId>datbase</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
    <!-- https://mvnrepository.com/artifact/org.jdbi/jdbi -->
        <dependency>
            <groupId>org.jdbi</groupId>
            <artifactId>jdbi</artifactId>
            <version>2.78</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.39</version>
        </dependency>
    </dependencies>


</project>

But when I run it I see:

The emoji is somehow been corrupted by JDBC. What can I try?

EDIT

I've managed to read out the emoji by implementing the method:

private String convertToUTF8(String str) {

    if (str == null) {
        return "";
    }

    try {
        byte[] ptext = str.getBytes("ISO-8859-1");
        return new String(ptext, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        log.error("problem converting delivery.message to UTF-8: " + e.toString());
    }

    return "";
}

Now I can see the emoji in the console. There's another issue now: this works with my local mysql DB but not with the one on AWS. I ran some queries:

show variables like 'collation%';

On local db it returned:

On the instance on AWS it returned:

So the difference is collation_server. And I can't figure out how to change this. I tried running:

ALTER DATABASE products CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;

But the collation_server value is still utf8mb4_unicode_ci.....