Java - How could change a relative URL String to an absolute URL if I know the domain?

Question

So I'm trying to make a very basic web browser that accomplishes very specific tasks. However, I need to get the URL from relative URLs (such as in tags. I can get both URLs, but I'm not sure how to approach relative URLs.

I am using Java 6 for compatibility with older systems (a lot older)

Basically, I have the URL "http://example.com/directory/page.html", then I have an tag with the href= "newpage.html". I want to be able to get the URL "http://example.com/directory/newpage.html".

Moreover, if its href= "../newpage.html", I want to get "http://example.com/newpage.html",

and if its href="http://example.org/dir/anotherpage.html", I want to get the URL "http://example.org/dir/anotherpage.html".

Is there any good, clean way of doing this?

Convert it to a URI and use its methods, then convert it back. You don't have to worry about the double dots. The Web server will understand them. — user207421
– user207421, Commented Mar 24, 2019 at 21:39

Samuel Philipp · Accepted Answer · 2019-03-25 18:14:10Z

1

You can simply use the uri.resolve() method.

First create a URI from the base URL you loaded in Browser:

URI uri = new URI("http://example.com/directory/page.html");
URI newpage = uri.resolve("newpage.html");
System.out.println(newpage);

This will print:

http://example.com/directory/newpage.html

The result for uri.resolve("../newpage.html") is :

http://example.com/newpage.html

The result for uri.resolve("http://example.org/dir/anotherpage.html") is:

http://example.org/dir/anotherpage.html

Of course you could check for an http prefix before and return the absolute URL instead of using uri.resolve().

Even the usage of anchors, like #myanchor is possible. The result of uri.resolve("#myanchor") is:

http://example.com/directory/page.html#myanchor

answered Mar 25, 2019 at 18:14

Samuel Philipp

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1 Comment

Hello234 Over a year ago

Worked exactly how I wanted! Thank you!

Not a JD · Accepted Answer · 2019-03-24 18:45:00Z

0

Take a look at Norconex commons-lang and the URLNormalizer. Examine how the method removeDotSegments() is implemented if you want to write the code yourself.

answered Mar 24, 2019 at 18:45

Not a JD

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