In Postgres database, there is a column type bytea. According to Storing Binary Data, here is the code to write files to bytea column with PreparedStatement:

File file = new File("myimage.gif");
try (FileInputStream fis = new FileInputStream(file);
        PreparedStatement ps = conn.prepareStatement("INSERT INTO images VALUES (?, ?)"); ) {
    ps.setString(1, file.getName());
    ps.setBinaryStream(2, fis, (int) file.length());  // <-- setBinaryStream needed here
    ps.executeUpdate();
}

For the current version of JdbcClient (6.1.1), StatementSpec.param() does not support InputStream. I have tried to open up underlying code and cannot find places where doing stream related code.

Missing this feature, will prevent JdbcClient to be used when bytea column exists.