spring boot or java read/open pdf url and ResponseEntity attachment file .pdf

1. Call the URL https://xxxxx.xxx/file.pdf
2. Read the file from step 1 and display it. By setting the response value as follows:

Content-Type : application/pdf
Content-Transfer-Encoding : binary
Content-disposition : attachment; filename=filename.pdf
Content-Length : xxxx

URL url = new URL(apiReportDomain
                  "/rest_v2/reports/reports/cms/loan_emergency/v1_0/RTP0003_02.pdf?i_ref_code="   documentId);
        System.out.println(url);
        String encoding = Base64.getEncoder().encodeToString(
                (apiReportUsername   ":"   apiReportPassword).getBytes(StandardCharsets.UTF_8));

        HttpURLConnection connectionApi = (HttpURLConnection) url.openConnection();
        connectionApi.setRequestMethod("GET");
        connectionApi.setDoOutput(true);
        connectionApi.setRequestProperty("Authorization", "Basic "   encoding);
        connectionApi.setRequestProperty("Content-Type", "application/pdf");
        InputStream content = connectionApi.getInputStream();
        BufferedReader in = new BufferedReader(
                new InputStreamReader(content));
                
        StringBuilder sb = new StringBuilder();
        int cp;
        while ((cp = in.read()) != -1) {
            sb.append((char) cp);
        }

        byte[] output = sb.toString().getBytes();

        HttpHeaders responseHeaders = new HttpHeaders();
        responseHeaders.set("charset", "utf-8");
        responseHeaders.setContentType(MediaType.valueOf("application/pdf"));
        responseHeaders.setContentLength(output.length);
        responseHeaders.set("Content-disposition", "attachment; filename=filename.pdf");

        return new ResponseEntity<byte[]>(output, responseHeaders, HttpStatus.OK);

enter image description here

which the result i got is a blank page But in fact, this PDF contains a full sheet of text.

CodePudding user response：

The issue is that the server needs to fetch the file from the internet, and then pass it on. Except of a redirect (which would look like cross-site traffic).

First write local code to fetch the PDF in a local test application. It could be that you need to use java SE HttpClient.

It just might be you need to fake a browser as agent, and accept cookies, follow a redirect. That all can be tested by a browser's development page looking at the network traffic in detail.

Then test that you can store a file with the PDF response.

And finally wire the code in the spring application, which is very similar on yielding the response. You could start with a dummy response, just writing some hard-coded bytes.

After info in the question

You go wrong in two points:

• PDFs are binary data, String is Unicode, with per char 2 bytes, requiring a conversion back and forth: the data will be corrupted and the memory usage twice, and it will be slow.

• String.getBytes(Charset) and new String(byte[], Charset) prevent that the default Charset of the executing PC is used.

• Keeping the PDF first entirely in memory is not needed. But then you are missing the Content-Length header.

    InputStream content = connectionApi.getInputStream();
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    content.transferTo(baos);
    byte[] output = baos.toByteArray();
  
    HttpHeaders responseHeaders = new HttpHeaders();
    responseHeaders.set("charset", "utf-8");
    responseHeaders.setContentType(MediaType.valueOf("application/pdf"));
    responseHeaders.setContentLength(output.length);
    responseHeaders.set("Content-disposition",
        "attachment; filename=filename.pdf");