will i be given a visa without an invitation since i already had a previous visa?

i stayed in china for three years but i am a nigerian so i came back to nigeria since 2005 to obtain a bachelors degree which i did recently. i did my o level while i was in china and obtain a degree and i also studied chinese for three months with a certificate. i want to go back to china to assist a friend in his studio and also search for employment, so will i be given a visa without an invitation since i already had a previous visa?