如何检查URL是否存在或返回Java的404？溶液

url java http-status-code-404

2022-08-31 13:08:54

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");
}

这应该打印

exists
does not exists

测试

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"));

输出

200
200
200
404

溶液

在 .connect（）之前添加下一行，输出将为 200、404、200、404

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)");

答案 1

您可能希望添加

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

如果您不想遵循重定向（3XX）

您不需要做“GET”，而是“HEAD”。

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

答案 2

这对我有用：

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);

感谢您的上述建议。