How to handle non-English IME keyboard inputs in GLFW?

[bowen951209]

    For example, I'm using Chinese IME. When I press a key, GLFW would not receive it. Instead, it popped up a small window displaying what character I typed. I want that when I press a key in Chinese IME, the small window wouldn't appear and I can send the key (and maybe translate it to an English character) to GLFW.
    I've seen a project which fulfill it in Minecraft. I want to know how it works and implement it in my Java/OpenGL program. Here is the picture of the small window(which I don't want).