java-cratedb download blob

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    if (req.getParameter("lsh") == null || req.getParameter("name") == null || req.getParameter("aaddr") == null) {
        throw new RuntimeException("Necessary Arg Missing");
    }
    String lsh= req.getParameter("lsh");
    String name= req.getParameter("name");
    String addr= req.getParameter("addr");
    String digest = "6f9ec32c2a08a5527f6932f9c9df90dfc1a0be85";//192.168.17.232:4300
    String filename = lsh + "_" + name+ "_" + addr;
    String surfix = ".pdf";
    String contentType = "application/octet-stream";
    OutputStream out = null;
    try {
        String sql = "SELECT * FROM " + table + " WHERE name = " + name+ " AND addr = " + addr;
        JSONObject reqJson = new JSONObject();
        reqJson.put("stmt", sql);
        JSONObject respJson = executeRequest(reqJson);
        if (respJson.getIntValue("code") == -1) {
            throw new RuntimeException("DonwloadInovice Error: Get digest from " + table + " occured error, please try later");
        }
        JSONArray respArr = respJson.getJSONArray("msg");
        JSONObject data = respArr.getJSONObject(0);
        digest = data.getString("pdfdigest");// To-do，這裏須要確認digest在數據庫中存儲到哪一個字段了
        InputStream is = downloadPdf(digest);
        resp.setHeader("Content-Type", contentType);
        resp.setHeader("Content-Transfer-Encoding", "binary");
        resp.setHeader("Cache-Control","must-revalidate");
        resp.setCharacterEncoding("UTF-8");
        resp.setHeader("Content-Disposition", "attachment;filename=" + filename + surfix);
        int read = -1;
        byte[] bytes = new byte[1024];
        out = resp.getOutputStream();
        while((read = is.read(bytes)) != -1) {
            out.write(bytes, 0, read);
        }
    }catch (Exception e) {
        e.printStackTrace();
        contentType = "text/html";
        resp.setHeader("Content-Type", contentType);
        String err = "downloadInvoice occured err, err message:" + e.getMessage();
        out.write(err.getBytes());
    } finally {
        if (null != out) {
            out.close();
        }
    }
}

private InputStream downloadPdf(String digest){
    try {
        HttpGet get = new HttpGet(blobUri(digest));
        CloseableHttpResponse response = httpClient.execute(get);
        InputStream is = response.getEntity().getContent();
        return is;
    }catch (Exception e){
        e.printStackTrace();
    }
    return null;
}

private String blobResourceUri(String index, String digest) {
    return String.format(Locale.ENGLISH, "%s/%s", index, digest);
}

private String blobUri(String digest) {
    return String.format(Locale.ENGLISH,
            "http://%s:%s/_blobs/%s", url, port, blobResourceUri(pdfblob, digest));
}

private JSONObject executeRequest(JSONObject jsonObject) {
    JSONObject respBO = new JSONObject();
    String pdfurl = "http://" + url + ":" + port + "/_sql?pretty";
    System.out.println(pdfurl);
    System.out.println(jsonObject);
    try {
        HttpPost httpPost = new HttpPost(pdfurl);
        HTTPResp resp = client.post(pdfurl, jsonObject);
        if (resp == null || resp.getRespCode(-1) != 200) {
            int errorCode = resp.getRespJson().getJSONObject("error").getIntValue("code");
            String errorMsg = resp.getRespJson().getJSONObject("error").getString("message");
            logger.error(" ----- execute failed :" + resp.getRespMsg());
            respBO.put("code", -1);
            respBO.put("msg", resp.getRespMsg());
        } else {
            logger.info(" ----- execute success");
            JSONObject respJson = resp.getRespJson();
            JSONArray respArray = reformatData(respJson);
            respBO.put("code", 0);
            respBO.put("msg", respArray);
        }
    }catch (Exception e) {
        e.printStackTrace();
        logger.error(e.getMessage(), e);
        respBO.put("code", -1);
        respBO.put("msg", e.getMessage());
    }
    return respBO;
}

private JSONArray reformatData(JSONObject arg) {
    JSONArray rows = arg.getJSONArray("rows");
    JSONArray cols = arg.getJSONArray("cols");
    JSONArray array = new JSONArray();
    for (int i = 0; i < rows.size(); i++) {
        JSONArray arr = rows.getJSONArray(i);
        JSONObject one = new JSONObject();
        for (int j = 0; j < arr.size(); j ++) {
            Object value = arr.get(j);
            String key = cols.getString(j);
            if (value == null) value = "null";//如果沒有值，則賦值爲null
            one.put(key, value);
        }
        array.add(one);
    }
    return array;
}

若是下載的文件有問題，那多是上傳的時候就有問題，能夠經過在瀏覽器輸入訪問地址，看可否獲取到相應的文件來檢查，官網樣例：

sh$ curl -isS '127.0.0.1:4200/_blobs/myblobs/e5fa44f2b31c1fb553b6021e7360d07d5d91ff5e'
HTTP/1.1 404 Not Found
Content-Length: 0

官網地址：https://crate.io/docs/reference/blob.html

當你輸入的digest和url時就能在瀏覽器上看到你的blob文件，若是看不到，那說明存儲到cratedb的文件是有問題的

提示：必定要確認存到cratedb的blob文件是可用的，不然白忙活了