1.首先在Application同级目录创建一个class：WebConfig
2.WebConfig继承WebMvcConfigureerAdapter,并重写addResourceHandlers方法；
3.添加配置：registry.addResourceHandler("/**").addResourceLocations("file:/Users/hou/Documents/imooc_upload/");
代码：
public class WebMvcConfig extends WebMvcConfigurerAdapter {
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/**").addResourceLocations("file:/Users/hou/Documents/imooc_upload/");
}
}
