Establishing SSL connection without server's identity verification is not recommended

SpringBoot 连接 MySQL 数据库，但是却获得以下错误信息提示：Warning：

Wed Dec 09 22:46:52 CET 2015 WARN: Establishing SSL connection without server‘s identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn‘t set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to ‘false‘. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.

This is the test class with the main method:

public class TestDatabase {

    public static void main(String[] args) {
        Database db = new Database();
        try {
            db.connect();
        } catch (Exception e) {
            e.printStackTrace();
        }
        db.close();
    }
}

This is the Database class:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class Database {

    private Connection con;

    public void connect() throws Exception{

        if(con != null) return;

        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            throw new Exception("No database");
        }

        String connectionURL = "jdbc:mysql://localhost:3306/Peoples";

        con = DriverManager.getConnection(connectionURL, "root", "milos23");        
    }

    public void close(){
        if(con != null){
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}