URL이 존재하는지 또는 Java에서 404를 반환하는지 확인하는 방법은 무엇입니까?

URL이 존재하는지 또는 Java에서 404를 반환하는지 확인하는 방법은 무엇입니까?

---

String urlString = "http://www.nbc.com/Heroes/novels/downloads/Heroes_novel_001.pdf";
URL url = new URL(urlString);
if(/* Url does not return 404 */) {
    System.out.println("exists");
} else {
    System.out.println("does not exists");
}
urlString = "http://www.nbc.com/Heroes/novels/downloads/Heroes_novel_190.pdf";
url = new URL(urlString);
if(/* Url does not return 404 */) {
    System.out.println("exists");
} else {
    System.out.println("does not exists");
}

이것은 인쇄되어야합니다

exists
does not exists

테스트

public static String URL = "http://www.nbc.com/Heroes/novels/downloads/";

public static int getResponseCode(String urlString) throws MalformedURLException, IOException {
    URL u = new URL(urlString); 
    HttpURLConnection huc =  (HttpURLConnection)  u.openConnection(); 
    huc.setRequestMethod("GET"); 
    huc.connect(); 
    return huc.getResponseCode();
}

System.out.println(getResponseCode(URL + "Heroes_novel_001.pdf")); 
System.out.println(getResponseCode(URL + "Heroes_novel_190.pdf"));   
System.out.println(getResponseCode("http://www.example.com")); 
System.out.println(getResponseCode("http://www.example.com/junk"));           

산출

200
200
200
404

해결책

.connect () 앞에 다음 줄을 추가하면 출력은 200, 404, 200, 404가됩니다.

huc.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.1.2) Gecko/20090729 Firefox/3.5.2 (.NET CLR 3.5.30729)");

---

추가 할 수 있습니다.

HttpURLConnection.setFollowRedirects(false);
// note : or
//        huc.setInstanceFollowRedirects(false)

리디렉션을 따르고 싶지 않은 경우 (3XX)

"GET"을 수행하는 대신 "HEAD"만 있으면됩니다.

huc.setRequestMethod("HEAD");
return (huc.getResponseCode() == HttpURLConnection.HTTP_OK);

---

이것은 나를 위해 일했습니다.

URL u = new URL ( "http://www.example.com/");
HttpURLConnection huc =  ( HttpURLConnection )  u.openConnection (); 
huc.setRequestMethod ("GET");  //OR  huc.setRequestMethod ("HEAD"); 
huc.connect () ; 
int code = huc.getResponseCode() ;
System.out.println(code);

위의 제안에 감사드립니다.

---

URL 개체 를 호출 하여 HttpUrlConnection 을 사용 openConnection()합니다.

getResponseCode () 는 연결에서 읽은 후 HTTP 응답을 제공합니다.

예 :

   URL u = new URL("http://www.example.com/"); 
   HttpURLConnection huc = (HttpURLConnection)u.openConnection(); 
   huc.setRequestMethod("GET"); 
   huc.connect() ; 
   OutputStream os = huc.getOutputStream(); 
   int code = huc.getResponseCode(); 

(검증되지 않은)

---

There is nothing wrong with your code. It's the NBC.com doing tricks on you. When NBC.com decides that your browser is not capable of displaying PDF, it simply sends back a webpage regardless what you are requesting, even if it doesn't exist.

You need to trick it back by telling it your browser is capable, something like,

conn.setRequestProperty("User-Agent",
    "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.0.13) Gecko/2009073021 Firefox/3.0.13");

---

Based on the given answers and information in the question, this is the code you should use:

public static boolean doesURLExist(URL url) throws IOException
{
    // We want to check the current URL
    HttpURLConnection.setFollowRedirects(false);

    HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();

    // We don't need to get data
    httpURLConnection.setRequestMethod("HEAD");

    // Some websites don't like programmatic access so pretend to be a browser
    httpURLConnection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.1.2) Gecko/20090729 Firefox/3.5.2 (.NET CLR 3.5.30729)");
    int responseCode = httpURLConnection.getResponseCode();

    // We only accept response code 200
    return responseCode == HttpURLConnection.HTTP_OK;
}

Of course tested and working.

참고URL : https://stackoverflow.com/questions/1378199/how-to-check-if-a-url-exists-or-returns-404-with-java