解决方式一
编写过滤器，对下载文件进行过滤，增加 跨域 响应头：
package top.malaoshi.netdisk.filter;
import top.malaoshi.util.StringUtil;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;
/**
* 解决 使用 uni.download() 下载图片跨域的过滤器
*/
@WebFilter("/upload/*")
public class F0UploadFilter implements Filter {
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) servletRequest;
HttpServletResponse resp = (HttpServletResponse) servletResponse;
String servletPath = req.getServletPath();
String fileName = StringUtil.lastSlice(servletPath, "/", false);
resp.setHeader("Access-Control-Allow-Origin","*");
resp.setHeader("Access-Control-Allow-Methods","GET");
/*
设置Access-Control-Expose-Headers暴露Content-Disposition响应头
否则uniapp下载时要获取Content-Disposition，导致出现Refused to get unsafe header错误
*/
resp.setHeader("Access-Control-Expose-Headers", "Content-Disposition");
// 对文件名进行编码，对于标准英文名来说，没有任何变化
String fileNameEncode = URLEncoder.encode(fileName, "UTF-8");
resp.addHeader("Content-Disposition", "attachment;filename=" + fileNameEncode);
filterChain.doFilter(servletRequest, servletResponse);
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void destroy() {
}
}
参考：
https://wenku.csdn.net/answer/3a2y795u05
解决方式二
如果部署到 Nginx ，图片通过 nginx 跨域，在 Nginx 增加响应头
在网站的cofig文件配置如下：
location ~ ..(gif|jpg|jpeg|png|bmp|swf)$
{
add_header Access-Control-Allow-Origin ;
add_header Access-Control-Allow-Headers X-Requested-With;
add_header Access-Control-Allow-Methods GET,POST,OPTIONS;
expires 30d;
error_log off;
access_log /dev/null;
}