Pay.java　为测试入口
WeixinApiResultImpl.java 为解析请求返回的结果，并有有将支付链接的URL转为二维码图片流的方法。
WeixinPayApiImpl.java 为请求前的操作（参数封装）(Pay.java is the test entry
WeixinApiResultImpl.java returns the result of the parsing request and has the method of converting the paid link URL to a two-dimensional code picture stream.
WeixinPayApiImpl.java for pre - request operations (parameter encapsulation))