A longtime US ally may soon be home to a Chinese military base

I am trying to understand the logic of such a move. These countries border each other. China has a base in Djibouti now. In addition to the buildup in the Spratly Islands. It doesn't seem to be an Iron Curtain buildup, exactly. This seems more like an opportunity for spying or capturing information on foreign technology to me. Or perhaps an effort to reach from both sides to control oil flow through the Persian/Arab Gulf. They do import a lot of oil. That could really play into world politics...