网络编程之:检查URL所指定的图片是否存在

可以利用java.net.HttpURLConnection内的getResponseCode()去检查应答代码(Response Code)

URL url = new URL( postURL );
HttpURLConnection urlcon = (HttpURLConnection) url.openConnection( );
urlcon.setRequestMethod("POST");
urlcon.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
if ( urlcon.getResponseCode( ) != HttpURLConnection.HTTP_OK ) {
    System.out.println("Posted ok!");
} else {
    System.out.println("Bad post...");
    return;
}

Response Code在Java API Doc的HttpURLConnection有详细的定义，如上例的HTTP_OK。

常用的Response Code:
200 OK
400 Bad Request
401 Unauthorized
403 Forbidden
404 Not Found

参考: http://www.ietf.org/rfc/rfc2616.txt (RFC2616)