java - 如何验证 URL 在 Java 1.6 中是否有效？

Question

我的应用程序处理用户手动输入的 URL。我发现某些格式错误的 URL(如“http:/not-valid”)会导致在打开连接时抛出 NullPointerException。正如我从 this Java bug report 中了解到的那样，该问题是已知的，不会被修复。建议使用 java.net.URI，它“更符合 RFC 2396”。

问题是:如何使用 URI 解决这个问题？我唯一能用 URI 做的就是用它来解析字符串并生成 URL。我准备了以下程序:

import java.net.*;

public class Test
{
    public static void main(String[] args)
    {
       try {
           URI uri = URI.create(args[0]);
           Object o = uri.toURL().getContent(); // try to get content
       }
       catch(Throwable e) {
           e.printStackTrace();
       }
    }
}

这是我的测试结果(使用 java 1.6.0_20)，与我使用 java.net.URL 得到的结果没有太大区别:

sh-3.2$ java Test url-not-validjava.lang.IllegalArgumentException: URI is not absolute        at java.net.URI.toURL(URI.java:1080)        at Test.main(Test.java:9)sh-3.2$ java Test http:/url-not-validjava.lang.NullPointerException        at sun.net.www.ParseUtil.toURI(ParseUtil.java:261)        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:795)        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:726)        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)        at java.net.URLConnection.getContent(URLConnection.java:688)        at java.net.URL.getContent(URL.java:1024)        at Test.main(Test.java:9)sh-3.2$ java Test http:///url-not-validjava.lang.IllegalArgumentException: protocol = http host = null        at sun.net.spi.DefaultProxySelector.select(DefaultProxySelector.java:151)        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:796)        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:726)        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)        at java.net.URLConnection.getContent(URLConnection.java:688)        at java.net.URL.getContent(URL.java:1024)        at Test.main(Test.java:9)sh-3.2$ java Test http:////url-not-validjava.lang.NullPointerException        at sun.net.www.ParseUtil.toURI(ParseUtil.java:261)        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:795)        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:726)        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)        at java.net.URLConnection.getContent(URLConnection.java:688)        at java.net.URL.getContent(URL.java:1024)        at Test.main(Test.java:9)

Answer 1

您可以使用 appache Validator Commons ..

UrlValidator urlValidator = new UrlValidator();
urlValidator.isValid("http://google.com");

http://commons.apache.org/validator/

http://commons.apache.org/validator/api-1.3.1/