使用Java进行完整链接提取

Question

My goal is to always get the same string (which is the URI in my case) while reading the href property from a link. Example: Suppose think that a html file it have somany links like
a href="index.html"> but base domain is http://www.domainname.com/index.html
a href="../index.html"> but base domain is http://www.domainname.com/dit/index.html
how can i get all the link correctly means the full link including domain name?
how can i do that in java?
the input is HTML,that is,from a bunch of HTML code it need to extract correct link

Answer 1

You can do this using a fullworthy HTML parser like Jsoup . There's a Node#absUrl() which does exactly what you want.

package com.stackoverflow.q3394298;

import java.net.URL;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;

public class Test {

    public static void main(String... args) throws Exception {
        URL url = new URL("https://stackoverflow.com/questions/3394298/");
        Document document = Jsoup.connect(url).get();
        Element link = document.select("a.question-hyperlink").first();
        System.out.println(link.attr("href"));
        System.out.println(link.absUrl("href"));
    }

}

which prints (correctly) the following for the title link of your current question:

/questions/3394298/full-link-extraction-using-java
https://stackoverflow.com/questions/3394298/full-link-extraction-using-java

Jsoup may have more other (undiscovered) advantages for your purpose as well.

Related questions:

• What are the pros and cons of the leading HTML parsers in Java?

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Update : if you want to select all links in the document, then do as follows:

        Elements links = document.select("a");
        for (Element link : links) {
            System.out.println(link.attr("href"));
            System.out.println(link.absUrl("href"));
        }

Answer 2

Use the URL object:

URL url = new URL(URL context, String spec)

Here's an example:

import java.net.*;

public class Test {
public static void main(String[] args) throws Exception {
   URL base = new URL("http://www.java.com/dit/index.html");   
   URL url = new URL(base, "../hello.html");

   System.out.println(base);
   System.out.println(url);
}
}

It will print:

http://www.java.com/dit/index.html
http://www.java.com/hello.html