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in Opentelemetry, not able to get parent span

I am new to OpenTelemetry word. I have created spans for my services separately, but when i am try to combine spans of two different services, using context propogation, I am not able to do it successfully.
I have used following code:
// at client side:
public static void sendContext(String resource) {
TextMapSetter<HttpURLConnection> setter =
new TextMapSetter<HttpURLConnection>() {
#Override
public void set(HttpURLConnection carrier, String key, String value) {
carrier.setRequestProperty(key, value);
}
};
HttpURLConnection transportLayer = null;
String urlString = "http://127.0.0.1:8080" + resource;
try {
URL url = new URL(urlString);
transportLayer = (HttpURLConnection) url.openConnection();
} catch (MalformedURLException ex) {
System.out.println(ex.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}
GlobalOpenTelemetry.getPropagators()
.getTextMapPropagator()
.inject(Context.current(), transportLayer, setter);
}
// at server side:
public static Context getContext(HttpServletRequest request) {
TextMapGetter<HttpServletRequest> getter =
new TextMapGetter<HttpServletRequest>() {
#Override
public String get(HttpServletRequest carrier, String key) {
Enumeration<String> headerNames = carrier.getHeaderNames();
if (headerNames != null) {
while (headerNames.hasMoreElements()) {
String headerName = headerNames.nextElement();
System.out.println("headerNames.nextElement(): " + headerName);
if (headerName.equals(key)) {
String headerValue = request.getHeader(headerName);
System.out.println("headerValue): " + headerValue);
return headerValue;
}
}
}
return null;
}
#Override
public Iterable<String> keys(HttpServletRequest carrier) {
Set<String> set = new HashSet<String>();
Enumeration<String> headerNames = carrier.getHeaderNames();
if (headerNames != null) {
while (headerNames.hasMoreElements()) {
set.add(headerNames.nextElement());
}
}
return set;
}
};
Context extractedContext =
GlobalOpenTelemetry.getPropagators()
.getTextMapPropagator()
.extract(Context.current(), request, getter);
At server, i am not able to get parent span.
Kindly help on this.

You can refer to OpenTelemetry main documentation from here. It contains the context propagation part but I used HttpHeader type getter as the TextMapGetter with the same functionality which shows in the doc and instead of using
Scope scope = extractedContext.makeCurrent()
as the scope to create a child span, better to use directly without the scope,
tracer.spanBuilder(spanName).setParent(extractedContext)
Because sometimes the automated way to propagate the parent span on the current thread does not work fine.

How could I download a PDF generated without store it on the server?

I have a Jhipster application that generate PDF with iText library, this PDF is saved in the computer in the route that I indicated.
I would like that when generating the pdf, a dialog box will appear to download the pdf. I am indifferent if the pdf is saved in the project folder or not saved in any place.
I have seen many posts giving possible answers on this page and on the internet, but many are already obsolete and others have not worked for me.
generatePDF
public void generatePDF(User u) {
String dest = "D:/PDF/result.pdf";
String src = "D:/PDF/template.pdf";
try {
PdfDocument pdf = new PdfDocument(new PdfReader(src), new PdfWriter(dest));
PdfAcroForm form = PdfAcroForm.getAcroForm(pdf, true);
Map<String, PdfFormField> fields = form.getFormFields();
fields.get("name").setValue(u.getFirstName());
fields.get("surname").setValue(u.getLastName());
fields.get("email").setValue(u.getEmail());
pdf.close();
} catch (IOException e) {
log.debug(e.getMessage());
}
}
UserResource
#GetMapping("/print-user/{id}")
#Timed
public ResponseEntity<User> printUserTemplate(#PathVariable Long id) {
User user = userRepository.findOne(id);
userService.generatePDF(user);
return ResponseUtil.wrapOrNotFound(Optional.ofNullable(user));
}
EDIT
entity.component.ts
downloadFile() {
this.entityService.downloadFile().subscribe();
}
entity.service.ts
downloadFile(): Observable<any> {
return this.http.get(SERVER_API_URL + 'api/downloadFile');
}

Use this to download the file:
#GetMapping("/downloadFile")
public ResponseEntity<Resource> downloadFile(HttpServletRequest request) {
// Load file as Resource
Resource resource = testService.loadFileAsResource();
// Try to determine file's content type
String contentType = null;
try {
contentType = request.getServletContext().getMimeType(resource.getFile().getAbsolutePath());
} catch (IOException ex) {
log.info("Could not determine file type.");
}
// Fallback to the default content type if type could not be determined
if (contentType == null) {
contentType = "application/octet-stream";
}
return ResponseEntity.ok().contentType(MediaType.parseMediaType(contentType)).header(
HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"").body(resource);
}
And this to generate the file:
public Resource loadFileAsResource() {
try {
Path path = Paths.get("D:\\PDF\\template.pdf");
Path filePath = path.normalize();
Resource resource = new UrlResource(filePath.toUri());
if (resource.exists()) {
return resource;
} else {
return null;
}
} catch (MalformedURLException ex) {
ex.printStackTrace();
return null;
}
}
References:
https://www.callicoder.com/spring-boot-file-upload-download-rest-api-example/
download a file from Spring boot rest service

Using Optional<T> from java SE 8

Hi I want to know how I can use Optional in java SE 8 in the function below.
public URL getAuthenticatedURL() throws MalformedURLException {
if (log != null){
log.writeINFOToLog("Fetching authentication URL...");
}
else{
Log.initLog();
log.writeINFOToLog("Fetching authentication URL...");
}
try{
String url = String.format("%s://%s%s?username=%s&password=%s",getProtocol(), getHost(), getPath(), getUsername(), getPassword());
URL returnURL = new URL(url);
return returnURL;
}
catch (MalformedURLException ex){
log.writeExceptionToLog(ex);
return null;
}
}
I want to be able to handle the scenario where values involved in constructing the URL is null or empty.

After some research, I think its best that I avoid nulls, since it does not make much sense to have a null.
Here is my code snippet of the same function once I have used Optional<URL>
public Optional<URL> getAuthenticatedURL() throws MalformedURLException {
if (log != null){
log.writeINFOToLog("Fetching authentication URL...");
}
else{
Log.initLog();
log.writeINFOToLog("Fetching authentication URL...");
}
String url = String.format("%s://%s%s?username=%s&password=%s",getProtocol(), getHost(), getPath(), getUsername(), getPassword());
return Optional.ofNullable(new URL(url));
}
So when I call the function the code will be something like this.
if(getAuthenticatedURL.isPresent()){
URL val = getAuthenticatedURL.get();
}

I think it is more reasonable to use Supplier than Optional, because getAuthenticatedURL() has no argument and generates an Object(URL).
It looks like:
Supplier<URL> supplier = () -> {
...
try {
return new URL(...);
} catch (MalformedURLException e) {
return null;
}
};
URL url = supplier.get();

How to get Current Absolute URL with Query String in JSF?

I am trying to get the absolute URL in my managed bean's action listener. I have used:
HttpServletRequest#getRequestURL() // returning http://localhost:7101/POSM/pages/catalog-edit
HttpServetRequest#getQueryString() // returning _adf.ctrl-state=gfjk46nd7_9
But the actual URL is: http://localhost:7101/POSM/pages/catalog-edit?_adf.ctrl-state=gfjk46nd7_9&articleReference=HEN00067&_afrLoop=343543687406787. I don't know why the parameter artcileReference get omitted.
Is there any method which can give me the whole URL at once? How can I get the whole URL with all query string?

You can reconstruct your URL manually by using ServletRequest#getParameterNames() and ServletRequest#getParameter() both available with the HttpServletRequest instance.
Here is a sample code I've used in the past for this exact purpose :
private String getURL()
{
Enumeration<String> lParameters;
String sParameter;
StringBuilder sbURL = new StringBuilder();
Object oRequest = FacesContext.getCurrentInstance().getExternalContext().getRequest();
try
{
if(oRequest instanceof HttpServletRequest)
{
sbURL.append(((HttpServletRequest)oRequest).getRequestURL().toString());
lParameters = ((HttpServletRequest)oRequest).getParameterNames();
if(lParameters.hasMoreElements())
{
if(!sbURL.toString().contains("?"))
{
sbURL.append("?");
}
else
{
sbURL.append("&");
}
}
while(lParameters.hasMoreElements())
{
sParameter = lParameters.nextElement();
sbURL.append(sParameter);
sbURL.append("=");
sbURL.append(URLEncoder.encode(((HttpServletRequest)oRequest).getParameter(sParameter),"UTF-8"));
if(lParameters.hasMoreElements())
{
sbURL.append("&");
}
}
}
}
catch(Exception e)
{
// Do nothing
}
return sbURL.toString();
}

Here I came up with my solution, taking idea of the answer given by Alexandre, considering that HttpServletRequest#getParameterValues() method:
protected String getCurrentURL() throws UnsupportedEncodingException {
Enumeration parameters = getServletRequest().getParameterNames();
StringBuffer urlBuffer = new StringBuffer();
urlBuffer.append(getServletRequest().getRequestURL().toString());
if(parameters.hasMoreElements()) {
if(!urlBuffer.toString().contains("?")) {
urlBuffer.append("?");
} else {
urlBuffer.append("&");
}
}
while(parameters.hasMoreElements()) {
String parameter = (String)parameters.nextElement();
String[] parameterValues = getServletRequest().getParameterValues(parameter);
if(!CollectionUtils.sizeIsEmpty(parameterValues)) {
for(int i = 0; i < parameterValues.length; i++) {
String value = parameterValues[i];
if(StringUtils.isNotBlank(value)) {
urlBuffer.append(parameter);
urlBuffer.append("=");
urlBuffer.append(URLEncoder.encode(value, "UTF-8"));
if((i + 1) != parameterValues.length) {
urlBuffer.append("&");
}
}
}
}
if(parameters.hasMoreElements()) {
urlBuffer.append("&");
}
}
return urlBuffer.toString();
}

posting data to a servlet using httpclient

I'm trying to post 2 fields, id and data, to a servlet using HttpClient.
The problem is that if the length of the data field is less than 1MB or so, the servlet will get what I posted. But if the length of the data field is larger than 1MB or so, the servlet will receive null for all fields. What am I missing here? Thanks.
Here's the sample data that I post to the servlet:
id=12312123123123
data=the content of a file that is base-64 encoded
Here's the method that I use to post data to the servlet.
private byte[] post(String aUrl,
Map<String,String> aParams,
String aCharsetEnc,
int aMaxWaitMs) throws Exception
{
PostMethod post = null;
try
{
HttpClient client = new HttpClient();
post = new PostMethod(aUrl);
post.setRequestHeader("Content-Type", "application/x-www-form-urlencoded; charset=" + aCharsetEnc);
for (String key : aParams.keySet())
{
post.addParameter(key, aParams.get(key));
}
final int code = client.executeMethod(post);
if (code == HttpStatus.SC_NO_CONTENT || code == HttpStatus.SC_NOT_FOUND)
{
return null;
}
else if (code != HttpStatus.SC_OK)
{
throw new HttpException("Error code " + code + " encountered.");
}
InputStream stream = post.getResponseBodyAsStream();
if (stream != null)
{
return BlobHelper.readBytes(stream);
}
return null;
}
finally
{
if (post != null)
{
post.releaseConnection();
}
}
}
Here's the method of the servlet.
public void doPost(HttpServletRequest aReq, HttpServletResponse aResp)
throws ServletException, IOException
{
setNoCache(aResp);
aResp.setContentType("text/plain");
try
{
final String id = aReq.getParameter(PARAM_ID);
final String dataStr = aReq.getParameter(PARAM_DATA);
if (log().isDebugEnabled())
{
log().debug("id=" + id);
log().debug("data=" + dataStr);
}
}
catch (Exception e)
{
}
}

Usually servlet containers have a maximum post size parameter.
For Tomcat you can follow the steps documented here(they should be similar for other appservers) -
Is there a max size for POST parameter content?