服务端读取图片内容返回前端，解决图片跨域问题

最近在配合前端开发，开发一个图片裁剪功能的时候，遇到一个oss图片跨域请求，无法访问的问题，索性自己写个接口，先读取图片文件流再直接返回前端。具体代码如下。

1.新建文件流内容封装类FileContent

public class FileContent {
    private byte[] content;
    private String content_type;

    public byte[] getContent() {
        return content;
    }

    public void setContent(byte[] content) {
        this.content = content;
    }

    public String getContent_type() {
        return content_type;
    }

    public void setContent_type(String content_type) {
        this.content_type = content_type;
    }
}

2.根据图片链接获取文件流

public static FileContent getImageByte(String img){
        //String imgUrl="http://mmbiz.qpic.cn/mmbiz/yqVAqoZvDibEaicDyIvX7dLE9icYnwb2tlOtSzGMCglvqk61JjpW338xMSlJsKPVBiaD6FY1M5MtopJYvWrVYeYwFA/0?wx_fmt=jpeg";
        ByteArrayOutputStream outStream = null;
        FileContent file=new FileContent();
        String contentType="";
        try {
            URL url=new URL(img);
            HttpURLConnection conn = (HttpURLConnection)url.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(10 * 1000);
            contentType=conn.getHeaderField("Content-Type");
            //通过输入流获取图片数据
            InputStream inStream = conn.getInputStream();

            outStream = new ByteArrayOutputStream();

            byte[] buffer = new byte[1024];
            int len = 0;
            while( (len=inStream.read(buffer)) != -1 ){
                outStream.write(buffer, 0, len);
            }
            inStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        byte[] content= outStream.toByteArray();
        file.setContent(content);
        file.setContent_type(contentType);

        return file;
    }

3.接口获取参数图片链接

 @RequestMapping("/read/image")
    public ResponseEntity<byte[]> getImageContent(HttpServletRequest request){
        HttpHeaders responseHeaders = new HttpHeaders();

        String imageUrl=request.getParameter("imageUrl");
        FileContent file=Utilities.getImageByte(imageUrl);

        responseHeaders.set("Access-Control-Allow-Origin","*");
        responseHeaders.set("Content-Type",file.getContent_type());

        return new ResponseEntity<>(file.getContent(), responseHeaders, HttpStatus.OK);
    }

4.前端可直接通过 域名+/read/image?imageUrl=XXXX调用网络图片，即可完美解决图片跨域问题。