确定字符串是否是java中的绝对URL或相对URL

给定一个字符串，如何确定它是Java中的绝对URL还是相对URL？ 我尝试了以下代码：

private boolean isAbsoluteURL(String urlString) { boolean result = false; try { URL url = new URL(urlString); String protocol = url.getProtocol(); if (protocol != null && protocol.trim().length() > 0) result = true; } catch (MalformedURLException e) { return false; } return result; } 

问题是所有相对URL都抛出了MalformedURLException，因为没有定义协议（例如：www.google.com和/ questions / ask）。

Answer 1

怎么样：

 final URI u = new URI("http://www.anigota.com/start"); // URI u = new URI("/works/with/me/too"); // URI u = new URI("/can/../do/./more/../sophis?ticated=stuff+too"); if(u.isAbsolute()) { System.out.println("Yes, i am absolute!"); } else { System.out.println("Ohh noes, it's a relative URI!"); } 

详情请见： http ： //docs.oracle.com/javase/7/docs/api/java/net/URI.html

HTH

Answer 2

这是我用来确保链接是绝对的片段：

  private String ensureAbsoluteURL(String base, String maybeRelative) { if (maybeRelative.startsWith("http")) { return maybeRelative; } else { try { return new URL(new URL(base), maybeRelative).toExternalForm(); } catch (MalformedURLException e) { // do something } } } 

Answer 3

正如我所说的那样，您必须在检查之前规范化URL，并且规范化取决于您的应用程序，因为www.google.com不是绝对URL。 这是一个示例代码，可用于检查URL是绝对的：

 import java.net.URL; public class Test { public static void main(String [] args) throws Exception { String [] urls = {"www.google.com", "http://www.google.com", "/search", "file:/dir/file", "file://localhost/dir/file", "file:///dir/file"}; for(String url:urls) { System.out.println("`" + url + "' is " + (isAbsoluteURL(url)?"absolute":"relative")); } } public static boolean isAbsoluteURL(String url) throws java.net.MalformedURLException { final URL baseHTTP = new URL("http://example.com"); final URL baseFILE = new URL("file:///"); URL frelative = new URL(baseFILE, url); URL hrelative = new URL(baseHTTP, url); System.err.println("DEBUG: file URL: " + frelative.toString()); System.err.println("DEBUG: http URL: " + hrelative.toString()); return frelative.equals(hrelative); } } 

运行：

 ~$ java Test 2>/dev/null `www.google.com' is relative `http://www.google.com' is absolute `/search' is relative `file:/dir/file' is absolute `file://localhost/dir/file' is absolute `file:///dir/file' is absolute 

Answer 4

我做的

 public static String processUrl(String urlToProcess, String grantedNormalUrl){ if (urlToProcess.startsWith("//")){ urlToProcess = checkUrlStartsWithProtocol(urlToProcess); return urlToProcess; } if (!isAbsolute(urlToProcess)){ String rootPage = extractRootPage(grantedNormalUrl); boolean domainEndsWithSlash = rootPage.endsWith("/"); boolean urlStartsWithSlash = urlToProcess.startsWith("/"); if (domainEndsWithSlash && urlStartsWithSlash){ rootPage = rootPage.substring(0, rootPage.length() - 1); // exclude / } urlToProcess = rootPage + (!(domainEndsWithSlash || urlStartsWithSlash) ? "/" : "") + urlToProcess; } return urlToProcess; } public static boolean isAbsolute(String url){ if (url.startsWith("//")) { // //www.domen.com/start return true; } if (url.startsWith("/")){ // /somePage.html return false; } boolean result = false; try { URI uri = new URI(url); result = uri.isAbsolute(); } catch (URISyntaxException e) { e.printStackTrace(); } return result; } public static String checkUrlStartsWithProtocol(String url) { if (!url.startsWith("http://") && !url.startsWith("https://")) { StringBuilder prefixBuilder = new StringBuilder(); prefixBuilder.append("http:"); if (!url.startsWith("//")) { prefixBuilder.append("//"); } url = prefixBuilder.toString() + url; } return url; } public static String extractRootPage(String urlString) { int ignoreSlashes = 0; if (urlString.startsWith("http://") || urlString.startsWith("https://")) { ignoreSlashes = 2; } int endPosition = urlString.length(); for (int i = 0; i < urlString.length(); i++) { if (urlString.charAt(i) == '/') { if (ignoreSlashes == 0) { endPosition = i; //substring exclude / break; } else { ignoreSlashes--; } } } return checkUrlStartsWithProtocol(urlString.substring(0, endPosition)); }