java后端調用第三方接口返回圖片流給前端的具體代碼實現

更新時間：2024年02月13日 10:17:35 作者：Monameng

在前后端分離的開發(fā)中,經常會遇到需要從后端返回圖片流給前端的情況,下面這篇文章主要給大家介紹了關于java后端調用第三方接口返回圖片流給前端的具體代碼實現,需要的朋友可以參考下

一、背景

有個需求是這樣的，客戶端直接通過外網訪問oss獲取圖片需要額外付費，考慮到成本問題，修改技術方案為：客戶端將請求鏈接發(fā)給后端，后端根據請求做一定的截取或拼接，通過內網調用oss，再將下載下來的圖片流返回給前端。

圖片流，展現在頁面上就是直接返回一張圖片在瀏覽器上。

二、具體代碼展示

前端期望，如果異常，直接把http status返回非200

@Slf4j
@RestController
public class PictureController {
    @Autowired
    private PictureService pictureService;

    @RequestMapping(value = "getPicture")
    public void getPicture(String path, HttpServletResponse resp) {
        boolean picSuccess;
        // 注意：一定要有這步，否則圖片顯示不出來
        resp.setContentType(MediaType.IMAGE_JPEG_VALUE);
        long start = System.currentTimeMillis();
        try {
            picSuccess = pictureService.getOssPicture(path, resp);
            if (!picSuccess) {
                resp.setStatus(HttpServletResponse.SC_FORBIDDEN);
            }
        } catch (Exception e) {
            resp.setStatus(HttpServletResponse.SC_FORBIDDEN);
            log.error("下載圖片失?。。?);
        }
        log.info("cmd=/getPicture,param={},cost:{}", path, System.currentTimeMillis() - start);
    }
}

public interface PictureService {
    boolean getOssPicture(String path, HttpServletResponse resp) throws IOException;
}

@Slf4j
@Service
public class PictureServiceImpl implements PictureService {
    
    @Value("${alioss.ak}")
    private String accessKeyId;

    // http://*********.aliyuncs.com
    @Value("${url.prefix}")
    private String urlPrefix;

    @Value("${oss.connect.time:3000}")
    private int ossConnectTime;

    @Override
    public boolean getOssPicture(String path, HttpServletResponse resp) throws IOException {
        String url = getOssUrl(path);
        long st = System.currentTimeMillis();
        Request requestDownload = new Request.Builder()
                .url(url)
                .build();
        OkHttpClient client = new OkHttpClient();
        client = client.newBuilder().connectTimeout(ossConnectTime, TimeUnit.MILLISECONDS).build();
        Response responseDownload = client.newCall(requestDownload).execute();
        if (responseDownload.isSuccessful() && responseDownload.body() != null && responseDownload.body().byteStream() != null) {
            InputStream is = responseDownload.body().byteStream();
            writeImageFile(resp, is);
        } else {
            log.error("PictureServiceImpl-oss調用返回異常： url={}, data={}", url, responseDownload);
            return false;
        }
        long responseTime = System.currentTimeMillis() - st;
        log.info("request-oss cost:{}", responseTime);
        return true;
    }

    // base64解碼==這塊是與前端約定好的，我這邊要做的解碼
    private String getOssUrl(String path) throws UnsupportedEncodingException {
        final Base64.Decoder decoder = Base64.getDecoder();
        String decodePath = new String(decoder.decode(path), "UTF-8");
        StringBuffer buffer = new StringBuffer();
        String[] split = decodePath.split("&");
        for (int i = 0; i < split.length; i++) {
            if (!split[i].startsWith("Version")) {
                buffer.append(split[i]).append("&");
            }
        }
        log.info("getOssUrl={}", urlPrefix + buffer);
        buffer.append("OSSAccessKeyId=").append(accessKeyId);
        return urlPrefix + buffer;
    }

    /**
     * 將輸入流輸出到頁面
     *
     * @param resp
     * @param inputStream
     */
    public void writeImageFile(HttpServletResponse resp, InputStream inputStream) {
        OutputStream out = null;
        try {
            out = resp.getOutputStream();
            int len = 0;
            byte[] b = new byte[1024];
            while ((len = inputStream.read(b)) != -1) {
                out.write(b, 0, len);
            }
            out.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

三、總結

上面就是返回圖片流的方式；

補充：Java后端實現圖片上傳并返回文件流

/**
 * @ClassName:
 * @User: ljh
 * @Date: 2022/12/19 15:01
 */
@RestController
public class IoController {

    @GetMapping("/download")
    public void download(@RequestParam("file") MultipartFile file,
                         HttpServletResponse response) throws Exception {
        String path = "E://";
        String filename = URLEncoder.encode("test.png", "UTF-8");
        response.setContentType("application/x-download");
        response.setHeader("Content-Disposition", "attachment;filename=" + filename);//瀏覽器上提示下載時默認的文件名
        ServletOutputStream out = response.getOutputStream();
        InputStream stream = file.getInputStream();

        try {//讀取服務器上的文件
            byte buff[] = new byte[file.getBytes().length];
            int length = 0;
            while ((length = stream.read(buff)) > 0) {
                out.write(buff, 0, length);
            }

            File newFile =new File(path + filename);
            file.transferTo(newFile);

            stream.close();
            out.flush();
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

到此這篇關于java后端調用第三方接口返回圖片流給前端的具體代碼實現的文章就介紹到這了,更多相關java后端返回圖片流給前端內容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關文章希望大家以后多多支持腳本之家！

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