Prerequisites for openfire 3.10.2

1. I planned to useJava SE Development Kit 7u80 for openfire 3.10.2 any compatibility issues will come . Any recommendation for specific  java version .

2.For database i planned to use MYSQL 5.5 . What characterset i need to setup( "utf 8" or "utf8mb4") for database. I need a special characters support like  smiles .