blocks|key|317600|text|验证器包：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|317601|似乎有一个nice+package+by+Yonatan+Matalon+called+UrlUtil。引用其API：|offset|length|317602|isValidWebPageAddress(java.lang.String+address,+boolean+validateSyntax,+
++++++++++++++++++++++boolean+validateExistance)+
Checks+if+the+given+address+is+a+valid+web+page+address.|code-block|syntax|javascript|317603|Sun的方法-检查网络地址|317604|Sun的Java站点提供了用于验证URL的connect+attempt+as+a+solution。|317605|其他正则表达式代码片段：|317606|在Oracle's+site和weberdev.com上有正则表达式验证尝试。|317607|entityMap|0|LINK|mutability|MUTABLE|url|http://matalon.org/search-algorithms/doc/org/matalon/pagerankhits/util/UrlUtil.html|1|http://java.sun.com/developer/JDCTechTips/2003/tt0422.html|2|http://www.oracle.com/technology/sample_code/tech/java/codesnippet/xdk/schemavalidation/Validate.java|3|http://www.weberdev.com/get_example-4228.html^0|0|5|1A|0|0|0|0|L|T|1|0|0|1|D|2|F|C|3|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@]|9|@$D|18|E|19|1|1A]]|A|$]]|$1|F|3|G|5|H|7|1B|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|1C|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1D|8|@]|9|@$D|1E|E|1F|1|1G]]|A|$]]|$1|O|3|P|5|6|7|1H|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1I|8|@]|9|@$D|1J|E|1K|1|1L]|$D|1M|E|1N|1|1O]]|A|$]]|$1|S|3|-4|5|6|7|1P|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]|10|$5|V|W|X|A|$Y|11]]|12|$5|V|W|X|A|$Y|13]]|14|$5|V|W|X|A|$Y|15]]]]

<h3>validator package:</h3>

There seems to be a <a href="http://matalon.org/search-algorithms/doc/org/matalon/pagerankhits/util/UrlUtil.html" rel="nofollow noreferrer">nice package by Yonatan Matalon called UrlUtil</a>. Quoting its API:

<pre><code>isValidWebPageAddress(java.lang.String address, boolean validateSyntax, 
 boolean validateExistance) 
Checks if the given address is a valid web page address.
</code></pre>

<h3>Sun's approach - check the network address</h3>

Sun's Java site offers <a href="http://java.sun.com/developer/JDCTechTips/2003/tt0422.html" rel="nofollow noreferrer">connect attempt as a solution</a> for validating URLs.

<h3>Other regex code snippets:</h3>

There are regex validation attempts at <a href="http://www.oracle.com/technology/sample_code/tech/java/codesnippet/xdk/schemavalidation/Validate.java" rel="nofollow noreferrer">Oracle's site</a> and <a href="http://www.weberdev.com/get_example-4228.html" rel="nofollow noreferrer">weberdev.com</a>.

blocks|key|317616|text|考虑使用Apache+Commons+UrlValidator+class|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|317617|UrlValidator+urlValidator+=+new+UrlValidator();
urlValidator.isValid("http://my+favorite+site!");|code-block|syntax|javascript|317618|您可以设置几个属性来控制该类的行为，默认情况下接受http、https和ftp。|style|CODE|317619|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/validator/apidocs/org/apache/commons/validator/routines/UrlValidator.html^0|4|X|0|0|0|P|4|U|5|10|3|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@$A|10|B|11|K|L]|$A|12|B|13|K|L]|$A|14|B|15|K|L]]|9|@]|C|$]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

Consider using the <a href="http://commons.apache.org/validator/apidocs/org/apache/commons/validator/routines/UrlValidator.html" rel="noreferrer">Apache Commons UrlValidator class</a>

<pre><code>UrlValidator urlValidator = new UrlValidator();
urlValidator.isValid("http://my favorite site!");
</code></pre>

There are several properties that you can set to control how this class behaves, by default <code>http</code>, <code>https</code>, and <code>ftp</code> are accepted.

blocks|key|319571|text|从URI的源代码来看，|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|319572|public+URL(URL+context,+String+spec,+URLStreamHandler+handler)|code-block|syntax|javascript|319573|constructor比其他构造函数做更多的验证。你可以试试那个，但是YMMV。|319574|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/7/docs/api/java/net/URL.html#URL(java.net.URL,%2520java.lang.String,%2520java.net.URLStreamHandler)^0|1|3|0|0|0|B|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Judging by the source code for <code>URI</code>, the
<pre><code>public URL(URL context, String spec, URLStreamHandler handler)
</code></pre>
<a href="https://docs.oracle.com/javase/7/docs/api/java/net/URL.html#URL(java.net.URL,%20java.lang.String,%20java.net.URLStreamHandler)" rel="nofollow noreferrer">constructor</a> does more validation than the other constructors. You might try that one, but YMMV.

blocks|key|3275559|text|以下是我尝试并发现有用的方法，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3275560|URL+u+=+new+URL(name);+//+this+would+check+for+the+protocol
u.toURI();+//+does+the+extra+checking+required+for+validation+of+URI+|code-block|syntax|javascript|3275561|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here is way I tried and found useful,

<pre><code>URL u = new URL(name); // this would check for the protocol
u.toURI(); // does the extra checking required for validation of URI 
</code></pre>

blocks|key|3275598|text|我很想把这篇文章作为评论贴到Tendayi+Mawushe's+answer上，但我担心篇幅不够;)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3275599|这是Apache+Commons+UrlValidator+source中的相关部分。|3275600|/**
+*+This+expression+derived/taken+from+the+BNF+for+URI+(RFC2396).
+*/
private+static+final+String+URL_PATTERN+=
++++++++"/%5E(([%5E:/?#]%2B):)?(//([%5E/?#]*))?([%5E?#]*)(\\?([%5E#]*))?(#(.*))?/";
//+++++++++12++++++++++++3++4++++++++++5+++++++6+++7++++++++8+9

/**
+*+Schema/Protocol+(ie.+http:,+ftp:,+file:,+etc).
+*/
private+static+final+int+PARSE_URL_SCHEME+=+2;

/**
+*+Includes+hostname/ip+and+port+number.
+*/
private+static+final+int+PARSE_URL_AUTHORITY+=+4;

private+static+final+int+PARSE_URL_PATH+=+5;

private+static+final+int+PARSE_URL_QUERY+=+7;

private+static+final+int+PARSE_URL_FRAGMENT+=+9;|code-block|syntax|javascript|3275601|您可以很容易地从那里构建自己的验证器。|3275602|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/2230770/27862|1|http://commons.apache.org/validator/apidocs/src-html/org/apache/commons/validator/UrlValidator.html^0|E|O|0|0|U|6|1|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|F|3|G|5|H|7|14|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|15|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

I'd love to post this as a comment to <a href="https://stackoverflow.com/a/2230770/27862">Tendayi Mawushe's answer</a>, but I'm afraid there is not enough space ;)

This is the relevant part from the Apache Commons UrlValidator <a href="http://commons.apache.org/validator/apidocs/src-html/org/apache/commons/validator/UrlValidator.html" rel="nofollow noreferrer">source</a>:

<pre><code>/**
 * This expression derived/taken from the BNF for URI (RFC2396).
 */
private static final String URL_PATTERN =
 "/^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\\?([^#]*))?(#(.*))?/";
// 12 3 4 5 6 7 8 9

/**
 * Schema/Protocol (ie. http:, ftp:, file:, etc).
 */
private static final int PARSE_URL_SCHEME = 2;

/**
 * Includes hostname/ip and port number.
 */
private static final int PARSE_URL_AUTHORITY = 4;

private static final int PARSE_URL_PATH = 5;

private static final int PARSE_URL_QUERY = 7;

private static final int PARSE_URL_FRAGMENT = 9;
</code></pre>

You can easily build your own validator from there.

blocks|key|314679|text|我不喜欢其中的任何一个实现(因为它们使用的是Regex，这是一个昂贵的操作，或者是一个库，如果你只需要一个方法，那就是过度杀伤力)，所以我最终使用了java.net.URI类，并进行了一些额外的检查，并将协议限制为:+http，https，file，ftp，mailto，news，urn。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|314680|是的，捕获异常可能是一项开销很大的操作，但可能没有正则表达式那么糟糕：|314681|final+static+Set<String>+protocols,+protocolsWithHost;

static+{
++protocolsWithHost+=+new+HashSet<String>(+
++++++Arrays.asList(+new+String[]{+"file",+"ftp",+"http",+"https"+}+)+
++);
++protocols+=+new+HashSet<String>(+
++++++Arrays.asList(+new+String[]{+"mailto",+"news",+"urn"+}+)+
++);
++protocols.addAll(protocolsWithHost);
}

public+static+boolean+isURI(String+str)+{
++int+colon+=+str.indexOf(':');
++if+(colon+<+3)++++++++++++++++++++++return+false;

++String+proto+=+str.substring(0,+colon).toLowerCase();
++if+(!protocols.contains(proto))+++++return+false;

++try+{
++++URI+uri+=+new+URI(str);
++++if+(protocolsWithHost.contains(proto))+{
++++++if+(uri.getHost()+==+null)++++++return+false;

++++++String+path+=+uri.getPath();
++++++if+(path+!=+null)+{
++++++++for+(int+i=path.length()-1;+i+>=+0;+i--)+{
++++++++++if+("?<>:*%7C\"".indexOf(+path.charAt(i)+)+>+-1)
++++++++++++return+false;
++++++++}
++++++}
++++}

++++return+true;
++}+catch+(+Exception+ex+)+{}

++return+false;
}|code-block|syntax|javascript|314682|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I didn't like any of the implementations (because they use a Regex which is an expensive operation, or a library which is an overkill if you only need one method), so I ended up using the java.net.URI class with some extra checks, and limiting the protocols to: http, https, file, ftp, mailto, news, urn.

And yes, catching exceptions can be an expensive operation, but probably not as bad as Regular Expressions:

<pre><code>final static Set&lt;String&gt; protocols, protocolsWithHost;

static {
 protocolsWithHost = new HashSet&lt;String&gt;( 
 Arrays.asList( new String[]{ "file", "ftp", "http", "https" } ) 
 );
 protocols = new HashSet&lt;String&gt;( 
 Arrays.asList( new String[]{ "mailto", "news", "urn" } ) 
 );
 protocols.addAll(protocolsWithHost);
}

public static boolean isURI(String str) {
 int colon = str.indexOf(':');
 if (colon &lt; 3) return false;

 String proto = str.substring(0, colon).toLowerCase();
 if (!protocols.contains(proto)) return false;

 try {
 URI uri = new URI(str);
 if (protocolsWithHost.contains(proto)) {
 if (uri.getHost() == null) return false;

 String path = uri.getPath();
 if (path != null) {
 for (int i=path.length()-1; i &gt;= 0; i--) {
 if ("?&lt;&gt;:*|\"".indexOf( path.charAt(i) ) &gt; -1)
 return false;
 }
 }
 }

 return true;
 } catch ( Exception ex ) {}

 return false;
}
</code></pre>

blocks|key|3275674|text|我最喜欢的方法，没有外部库：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3275675|try+{
++++URI+uri+=+new+URI(name);

++++//+perform+checks+for+scheme,+authority,+host,+etc.,+based+on+your+requirements

++++if+("mailto".equals(uri.getScheme())+{/*Code*/}
++++if+(uri.getHost()+==+null)+{/*Code*/}

}+catch+(URISyntaxException+e)+{
}|code-block|syntax|javascript|3275676|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

My favorite approach, without external libraries:

<pre><code>try {
 URI uri = new URI(name);

 // perform checks for scheme, authority, host, etc., based on your requirements

 if ("mailto".equals(uri.getScheme()) {/*Code*/}
 if (uri.getHost() == null) {/*Code*/}

} catch (URISyntaxException e) {
}
</code></pre>

blocks|key|319660|text|最“万无一失”的方法是检查URL的可用性：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|319661|public+boolean+isURL(String+url)+{
++try+{
+++++(new+java.net.URL(url)).openStream().close();
+++++return+true;
++}+catch+(Exception+ex)+{+}
++return+false;
}|code-block|syntax|javascript|319662|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The most "foolproof" way is to check for the availability of URL:

<pre><code>public boolean isURL(String url) {
 try {
 (new java.net.URL(url)).openStream().close();
 return true;
 } catch (Exception ex) { }
 return false;
}
</code></pre>

What is the best way to check if a URL is valid in Java? 

If tried to call <code>new URL(urlString)</code> and catch a <code>MalformedURLException</code>, but it seems to be happy with anything that begins with <code>http://</code>.

I'm not concerned about establishing a connection, just validity. Is there a method for this? An annotation in Hibernate Validator? Should I use a regex?

Edit: Some examples of accepted URLs are <code>http://***</code> and <code>http://my favorite site!</code>.

How to check for a valid URL in Java?

Java

在Java中检查URL是否有效的最佳方法是什么？如果尝试调用new URL(urlString)并捕获MalformedURLException，但它似乎对任何以http://开头的内容都很满意。我关心的不是建立连接，而是有效性。有什么方法可以解决这个问题吗？Hibernate Validator中的注解？我应该使用正...

问如何在Java中检查有效的URL？
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