How can I get html error description from server when failing to load XML -SOLVED-

Programming Questions

v.k.

How can I get html error description from server when failing to load XML -SOLVED-

in Programming Questions • 3 months ago

I have this query for a server:

// temp is a String containing the URL

try{
xml = loadXML(temp);
}catch(Exception e){
e.printStackTrace();
}

I intentionally made a mistake in the URL. When I copy and paste the URL in browser (or click it here) the browser displays a nice message specifying the error made. " Missing parameter: autor". I'd like to access this information to display it to user. But the stackTrace is much more cryptographic (pasted at the end) and do not contains the useful message above... How could I get that message?

Any more info needed?

Processing 2.0 willing to be javaScript compatible.

thanks

edit:

this is the html in the page:

<html>
<head></head>
<body>
<pre style="word-wrap: break-word; white-space: pre-wrap;">Missing parameter: autor. </pre>
</body>
</html>

"Java.io.IOException: Server returned HTTP response code: 500 for URL: http://www.camara.gov.br/SitCamaraWS/Proposicoes.asmx/ListarProposicoes?sigla=PL&numero=&ano=1960&datApresentacaoIni=&datApresentacaoFim=&parteNomeAutor=&siglaPartidoAutor=&siglaUFAutor=&generoAutor=&IdSituacaoProposicao=&IdOrgaoSituacaoProposicao=&&codEstado=&codOrgaoEstado=&emTramitacao= at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1436) at java.net.URL.openStream(URL.java:1010) at processing.core.PApplet.createInputRaw(PApplet.java:6960) at processing.core.PApplet.createInput(PApplet.java:6928) at processing.core.PApplet.createReader(PApplet.java:6722) at processing.core.PApplet.loadXML(PApplet.java:6070) at processing.core.PApplet.loadXML(PApplet.java:6060) at buildingQuery2_class$Query.makeQuery(buildingQuery2_class.java:161) at buildingQuery2_class.setup(buildingQuery2_class.java:23) at processing.core.PApplet.handleDraw(PApplet.java:2245) at processing.core.PGraphicsJava2D.requestDraw(PGraphicsJava2D.java:243) at processing.core.PApplet.run(PApplet.java:2141) at java.lang.Thread.run(Thread.java:680) http://www.camara.gov.br/SitCamaraWS/Proposicoes.asmx/ListarProposicoes?sigla=PL&numero=&ano=1960&datApresentacaoIni=&datApresentacaoFim=&parteNomeAutor=&siglaPartidoAutor=&siglaUFAutor=&generoAutor=&IdSituacaoProposicao=&IdOrgaoSituacaoProposicao=&&codEstado=&codOrgaoEstado=&emTramitacao= does not exist or could not be read java.net.MalformedURLException at java.net.URL.<init>(URL.java:601) at java.net.URL.<init>(URL.java:464) at java.net.URL.<init>(URL.java:413) at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:649) at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(XMLVersionDetector.java:186) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:772) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737) at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119) at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:232) at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:284) at processing.data.XML.<init>(XML.java:170) at processing.core.PApplet.loadXML(PApplet.java:6070) at processing.core.PApplet.loadXML(PApplet.java:6060) at buildingQuery2_class$Query.makeQuery(buildingQuery2_class.java:161) at buildingQuery2_class.setup(buildingQuery2_class.java:23) at processing.core.PApplet.handleDraw(PApplet.java:2245) at processing.core.PGraphicsJava2D.requestDraw(PGraphicsJava2D.java:243) at processing.core.PApplet.run(PApplet.java:2141) at java.lang.Thread.run(Thread.java:680)

Replies(7)

v.k.

Re: How can I get html error description from server when failing to load XML

3 months ago

Bumping and adding :)

If i do loadStrings("http://forum.processing.org") for instance i got all HTML as strings, that would be good enough for me, but with the error 500 in the url above I got an error and don't reach the HTML, but the browser does... How? The server serves some alternate html? Is there this address?

tks

PhiLho

Re: How can I get html error description from server when failing to load XML

3 months ago

I am not sure, but you can check the connection before trying to use it:

import java.net.*;
import java.io.*;
InputStream input = null;
try
{
URL url = new URL("http://Processing.org/unknown");
URLConnection connection = url.openConnection();
input = connection.getInputStream();
}
catch (Exception e)
{
println("Error " + e);
}
if (input != null)
{
String[] lines = loadStrings(input);
println(lines);
}

Note that loadXML() doesn't throw exceptions, Processing already intercepts them:

public XML loadXML(String filename, String options) {
try {
return new XML(createReader(filename), options);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}

This also shows how you can do a call and process the exception yourself...

PhiLho

Re: How can I get html error description from server when failing to load XML

3 months ago

Mmm, I started to write this some hours ago, before your update...
I also just noticed that I have the URL in the stack trace...
If I go there with Firefox, and view the source, I just get the error as plain text: no HTML there.
It is logical as a server just returns an header in this case.

PhiLho

Re: How can I get html error description from server when failing to load XML

3 months ago

A little more thorough code.
I wasn't able yet to get the explicit error message, alas.

import java.net.*;
import java.io.*;
String url1 = "http://www.camara.gov.br/SitCamaraWS/Proposicoes.asmx/ListarProposicoes?sigla=PL&numero=&ano=1960&datApresentacaoIni=&datApresentacaoFim=&parteNomeAutor=&siglaPartidoAutor=&siglaUFAutor=&generoAutor=&IdSituacaoProposicao=&IdOrgaoSituacaoProposicao=&&codEstado=&codOrgaoEstado=&emTramitacao=";
String url2 = "http://Processing.org";
// With information frm http://stackoverflow.com/questions/4596447/java-check-if-file-exists-on-remote-server-using-its-url
URL url = null;
try
{
url = new URL(url1);
}
catch (MalformedURLException e)
{
println("Error in URL " + e);
exit();
}
HttpURLConnection connection = null;
try
{
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("HEAD");
int code = connection.getResponseCode();
if (code != HttpURLConnection.HTTP_OK)
{
println("Answer: " + code + " - " + connection.getResponseMessage());
InputStream error = connection.getErrorStream();
if (error != null)
{
println("Error response:");
String[] lines = loadStrings(error);
println(lines);
error.close();
}
println("Error header:");
String field = null;
int i = 0;
do
{
field = connection.getHeaderField(i);
String key = connection.getHeaderFieldKey(i);
if (field != null)
{
println("Header " + i + ": " + (key == null ? "" : key + "=") + field);
}
i++;
} while (field != null);
println("End in error");
exit();
}
}
catch (IOException e)
{
println("Error in I/O " + e);
exit();
}
println("Correct data:");
InputStream input = null;
try
{
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
input = connection.getInputStream();
String[] lines = loadStrings(input);
println(lines);
}
catch (IOException e)
{
println("Error " + e);
}
finally
{
if (input != null)
{
try { input.close(); } catch (IOException e) {}
}
}
exit();

v.k.

Re: How can I get html error description from server when failing to load XML

3 months ago

Well, you did it! Amazing! Thanks a lot for your time. The only thing I tweaked was the parameter at line 21 from "HEAD" to "GET"

21. connection.setRequestMethod("GET");

And... voilà! There it is:

OUTPUT:

Answer: 500 - Internal Server Error.

Error response:

[0] "Missing parameter: autor."

Error header:

Header 0: HTTP/1.1 500 Internal Server Error.

Header 1: Date=Sat, 13 Jul 2013 02:41:18 GMT

...

Ready for use, nicely placed in an array :)

It seams that it comes in the errorStream of GET. Thanks a lot.

This solution , besides being brilliant, is not compatible with javaSript though... Is it?

So to put something online with it I would need to make an Applet, right?

I'll think about... I have no idea on how to make such a thing with plain js.

Anyway thanks a lot for your help.

PhiLho

Re: How can I get html error description from server when failing to load XML -SOLVED-

3 months ago

Ah, silly me, I indeed tried a GET later, but with the regular input stream, not the error one! Good catch.
Maybe my approach could have worked with other servers...

I also noticed a strange thing: I get both the
End in error
Correct data:
messages, which seem to imply that exit() is (no longer?) immediate... (might need a return after the exit()).

" not compatible with javaSript"
Alas... It is Java-specific. If JS is able to do this, I don't know how. Actually, I don't even know how to do cross-site requests in PJS. Classical ways I know in JS is to use iframes or JsonP requests.

" thanks a lot for your help"
No problem, it is by researching for such questions that I progress in my programming knowledge...

v.k.

Re: How can I get html error description from server when failing to load XML -SOLVED-

3 months ago

"t is by researching for such questions that I progress in my programming knowledge... "

that's the way i feel also, but i got much more room to progress than you :)

I think I may just link to the actual page for the error message to keep it compatible with JS...

we will see...

About the break I did not understood it also... But i thought it was me...

thx

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