autolink-java

Java library to extract links such as URLs and email addresses from plain text. Fast, small and smart about recognizing where links end.

Inspired by Rinku. Similar to it, regular expressions are not used. Instead, the input text is parsed in one pass with limited backtracking.

This library requires Java 7. It works on Android (minimum API level 15). It has no external dependencies.

Maven coordinates (see here for other build systems):

<dependency>
    <groupId>org.nibor.autolink</groupId>
    <artifactId>autolink</artifactId>
    <version>0.7.0</version>
</dependency>

Usage

Extract links:

import org.nibor.autolink.*;

String input = "wow, so example: http://test.com";
LinkExtractor linkExtractor = LinkExtractor.builder()
        .linkTypes(EnumSet.of(LinkType.URL, LinkType.WWW, LinkType.EMAIL))
        .build();
Iterable<LinkSpan> links = linkExtractor.extractLinks(input);
LinkSpan link = links.iterator().next();
link.getType();        // LinkType.URL
link.getBeginIndex();  // 17
link.getEndIndex();    // 32
input.substring(link.getBeginIndex(), link.getEndIndex());  // "http://test.com"

Note that by default all supported types of links are extracted. If you're only interested in specific types, narrow it down using the linkTypes method.

There's also a static method to replace links found in the text. Here's an example of using that for wrapping URLs in an <a> tag. Note that it doesn't handle escaping at all:

import org.nibor.autolink.*;

String input = "wow http://test.com such linked";
LinkExtractor linkExtractor = LinkExtractor.builder()
        .linkTypes(EnumSet.of(LinkType.URL)) // limit to URLs
        .build();
Iterable<LinkSpan> links = linkExtractor.extractLinks(input);
String result = Autolink.renderLinks(input, links, (link, text, sb) -> {
    sb.append("<a href=\"");
    sb.append(text, link.getBeginIndex(), link.getEndIndex());
    sb.append("\">");
    sb.append(text, link.getBeginIndex(), link.getEndIndex());
    sb.append("</a>");
});
result;  // "wow <a href=\"http://test.com\">http://test.com</a> such linked"

Features

URL extraction

Extracts URLs of the form scheme://example with any potentially valid scheme. URIs such as example:test are not matched (may be added as an option in the future). If only certain schemes should be allowed, the result can be filtered. (Note that schemes can contain dots, so foo.http://example is recognized as a single link.)

Includes heuristics for not including trailing delimiters such as punctuation and unbalanced parentheses, see examples below.

Supports internationalized domain names (IDN). Note that they are not validated and as a result, invalid URLs may be matched.

Example input and linked result:

http://example.com. → http://example.com.
http://example.com, → http://example.com,
(http://example.com) → (http://example.com)
(... (see http://example.com)) → (... (see http://example.com))
https://en.wikipedia.org/wiki/Link_(The_Legend_of_Zelda) → https://en.wikipedia.org/wiki/Link_(The_Legend_of_Zelda)
http://üñîçøðé.com/ → http://üñîçøðé.com/

Use LinkType.URL for this, and see test cases here.

WWW link extraction

Extract links like www.example.com. They need to start with www. but don't need a scheme://. For detecting the end of the link, the same heuristics apply as for URLs.

Examples:

www.example.com. → www.example.com.
(www.example.com) → (www.example.com)
[..] link:www.example.com [..] → [..] link:www.example.com [..]

Not supported:

Uppercase www's, e.g. WWW.example.com and wWw.example.com
Too many or too few w's, e.g. wwww.example.com

The domain must have at least 3 parts, so www.com is not valid, but www.something.co.uk is.

Use LinkType.WWW for this, and see test cases here.

Email address extraction

Extracts emails such as foo@example.com. Matches international email addresses, but doesn't verify the domain name (may match too much).

Examples:

foo@example.com → foo@example.com
foo@example.com. → foo@example.com.
foo@example.com, → foo@example.com,
üñîçøðé@üñîçøðé.com → üñîçøðé@üñîçøðé.com

Not supported:

Quoted local parts, e.g. "this is sparta"@example.com
Address literals, e.g. foo@[127.0.0.1]

Note that the domain must have at least one dot (e.g. foo@com isn't matched), unless the emailDomainMustHaveDot option is disabled.

Use LinkType.EMAIL for this, and see test cases here.

Contributing

Pull requests, issues and comments welcome ☺. For pull requests:

Add tests for new features and bug fixes
Follow the existing style (always use braces, 4 space indent)
Separate unrelated changes into multiple pull requests

License

MIT licensed, see LICENSE file.

fatjyc/autolink-java