In a recent project, I had the pleasure of troubleshooting a bug that involved images not loading when spaces were in the filename. I thought "What a simple issue, I'll UrlEncode() it!" But, NAY! Simply using UrlEncode() didn't resolve the problem.
The new problem was the HttpUtilities.UrlEncode() method switched spaces () to plusses (+) instead of %20 like the browser wanted. So file+image+name.jpg would return not-found while file%20image%20name.jpg was found correctly.
Thankfully, a coworker pointed out HttpUtilities.UrlPathEncode() to me which uses %20 for spaces instead of +.
WHY are there two ways of handling Url encoding? WHY are there two commands that behave so differently?
UrlEncode is useful for use with a QueryString as browsers tend to use a + here in place of a space when submitting forms with the GET method.
UrlPathEncode simply replaces all characters that cannot be used within a URL, such as <, > and .
Both MSDN links include this quote:
You can encode a URL using with the UrlEncode method or the
UrlPathEncode method. However, the methods return different results.
The UrlEncode method converts each space character to a plus character
(+). The UrlPathEncode method converts each space character into the
string "%20", which represents a space in hexadecimal notation. Use
the UrlPathEncode method when you encode the path portion of a URL in
order to guarantee a consistent decoded URL, regardless of which
platform or browser performs the decoding.
So in a URL you have the path and then a ? and then the parameters (i.e. http://some_path/page.aspx?parameters). URL paths encode spaces differently then the url parameters, that's why there is the two versions. For a long time spaces were not valid in a URL, but were in in the parameters.
In other words the formatting urls has changed over time. For a long time only ANSI chars could be in a URL too.
Related
Why does the documentation of .NET for HttpUtility.UrlPathEncode for .NET 4.5 state
Do not use; intended only for browser compatibility. Use UrlEncode.
UrlEncode does not do the same, it encodes a string for the parameter part of a URL, not for the path part. Is there a better way to encode a string for the path part and why shouldn't I use this function, which is in the framework since 1.1 and works?
based on MSDN, they recommend to use UrlEncode to grantee that it is working for all platforms and browsers
You can encode a URL using with the UrlEncode method or the UrlPathEncode method. However, the methods return different results. The UrlEncode method converts each space character to a plus character (+). The UrlPathEncode method converts each space character into the string "%20", which represents a space in hexadecimal notation. Use the UrlPathEncode method when you encode the path portion of a URL in order to guarantee a consistent decoded URL, regardless of which platform or browser performs the decoding.
Also UrlEncode is using UTF-8 encoding so if you are sending query string in different language like Arabic you should use UrlEncode
Use Uri.EscapeUriString if you want encode a path of a URL. HttpUtility.UrlEncode is for query parameters and encode also slashes which is wrong for a path.
Failing to escape an "&" character in HTML markup creates an entity. It is often done inadvertently when linking URLs in a document, and W3C's Markup Validation Service will consider this an error.
I'm wondering, does ASP.NET's Response.Redirect method expect ampersands to be escaped in its url parameter? From reading its MSDN description, I honestly can't tell.
Pass the URL exactly as it should appear in the address bar in the web browser. For example, if you're trying to redirect to http://example.com/?foo=bar&baz=quux, then pass that exact string as-is to Response.Redirect.
try UrlEncode The UrlEncode(String) method can be used to encode the entire URL, including query-string values. If characters such as blanks and punctuation are passed in an HTTP stream without encoding, they might be misinterpreted at the receiving end. URL encoding converts characters that are not allowed in a URL into character-entity equivalents; URL decoding reverses the encoding. For example, when the characters < and > are embedded in a block of text to be transmitted in a URL, they are encoded as %3c and %3e. URLEncode
System.Web.HttpUtility.UrlEncode(string url)
I've created an API for use on my website.
The API I made strips everything using mysql_real_escape_string then puts it into the database.
But the problem I'm having is the URL that my php scripts are using to access the API is cut short sometimes...
Which I have narrowed down to one of the parameters...
When its Ford Mondeo 22' the URL that is passed to simplexml_load_file is
http://mydomain.com/api/create.xml?api_number=brho15p6z1dhqwf5tsff&env=live&number=AJ20023232&title=Ford Mondeo 22'&image=http://mydomain.com/wp-content/uploads/2012/10/914955-150x150.jpg
but the API reports back the URL accessed as
http://mydomain.com/api/create.xml?api_number=brho15p6z1dhqwf5tsff&env=live&number=AJ20023232&title=Ford
If I remove the single quote then everything works fine, any idea how to correct this I suspect there's something I've overlooked when passing variables in the URL
It is the spaces in the "Ford Mondeo 22'" value that is causing the problem. You cannot have a spaces in the URL. You need to use escape characters. The encoded version of the parameter should be
Ford%20Mondeo%2022'
%20 is the escape character for space
I.e. the whole URL should read as follows:
http://mydomain.com/api/create.xml?api_number=brho15p6z1dhqwf5tsff&env=live&number=AJ20023232&title=Ford%20Mondeo%2022'&image=http://mydomain.com/wp-content/uploads/2012/10/914955-150x150.jpg
EDIT:
Your comment indicates that you use PHP. In PHP, you can use urlencode($foo) and urldecode($foo) to switch between the normal string and the encoding string.
What I don't really understand is the benefit of using '?' instead of '&' in urls:
It makes nobody's life easier if we use a different character as the first separator character.
Can you come up with a reasonable explanation?
EDIT: after more research I found that "&" can be a part of file name (terms&conditions.html) so "?" is a good separator. But still I think using "?" for separators makes lives easier (from url generators and parsers point of view):
Is there any advantage in using "&" which is not clear at the first glance?
From the URI spec's (RFC 3986) point of view, the only separator here is "?". the format of the query is opaque; the ampersands just are something that HTML happens to use for form submissions.
The answer's pretty much in this article - http://www.skorks.com/2010/05/what-every-developer-should-know-about-urls/ . To highlight it, here goes :
Query is the preferred way to send some parameters to a resource on
the server. These are key=value pairs and are separated from the rest
of the URL by a ? (question mark) character and are normally separated
from each other by & (ampersand) characters. What you may not know is
the fact that it is legal to separate them from each other by the ;
(semi-colon) character as well. The following URLs are equivalent:
http://www.blah.com/some/crazy/path.html?param1=foo¶m2=bar
http://www.blah.com/some/crazy/path.html?param1=foo;param2
The RFC 3896 (https://www.ietf.org/rfc/rfc3986.txt) defines general and sub delimiters ... '?' is a general, '&' and ';' are sub. The spec is pretty clear about that.
In this case the latter '?' chars would be treated as part of the query. If the query parser follows the spec strictly, it would then pass the whole query on to the app-destination. If the app-destination could choose to further process the query string in a manner which treats the ? as a param name-value pairs delimiter, that is up to the app's designers.
My guess is that this often 'just works' because code that splits query strings and the original uri uses all delimiters for matching: 1) first query is split on '?' then 2) query string is parsed using char match list that includes '?' (convenience only).... This could be occurring in ubiquitous parsing libraries already.
In some javascript, I have:
var url = "find.aspx?" + "location=" + encodeURIComponent( address );
alert( url );
location.href = url;
where the value of address is the string "Seattle, WA".
In the alert I see
find.aspx?Seattle%2C%20WA
as I expect.
But on the server side, when I look at Request.Url, the relevant substring I see is
find.aspx?Seattle, WA
And in the Firefox url window I see
find.aspx?location=Seattle%2C WA
So I'm getting three different representations whereas I would expect that in all three places I should see what I see in the alert. My expectation is that the url I assign to location.href should show up as-is in the browser url window, and should be passed as-is to the server in Request.Url (and I would need to decode the values on the server before using them). What's happening?
Firefox converts certain encoded characters into their literal forms as a way to be friendly to users. It will also convert spaces typed into the address bar into %20 for the server.
Update: The reason Firefox doesn't display the comma unencoded is because commas are allowed in URLs, but spaces are not, so it knows that a space is going to be unambiguously interpreted, whereas the pre-encoded comma is different from a non-encoded comma to some servers. see: Can I use commas in a URL?
ASP is probably trying to help you out by auto-un-encoding the string for you.
Update: It looks like ASP.NET unencodes Request.Url for you by default, as mentioned here: QueryString malformed after URLDecode They also mention that you can use HttpRequest.Url.Query to access the un-decoded version.
The alert is the only thing not doing any "magic" for you.
For the alert, you are doing the encoding yourself. Perhaps it looks the same as on the server-side if you removed encodeURIComponent.
On the server side, ASP.NET will always show you the unencoded form. This is to make it easier to directly map to files that also have text that needed to be (un)encoded.
Note that you can replace every letter for its UTF8 representation in URL Encoding. It will still be the same URL. I.e., type the following in the browser window and it will still work: %66%59%6E%64.aspx?location=Seattle%2C%20WA. To only encode the necessary chars, use UrlEncode on the server side if you create a link yourself.
URL encoding can become fairly tricky. You ask to explain it. To know the correct escape of a certain character, you need to know how that character looks in UTF8. The hexadecimal value of the UTF-8 bytes then become the %XX%YY value of your letter. Sometimes it's one %XX, but it can be up to six byte sequences in total (some Chinese characters for instance).
URL Encoding works one way only. Never double-encode or double-unencode. This is prohibited by the specification. Also, because you can encode any character, it is not always possible (as you found out) to do roundtrip encoding/unencoding. If you unencode and re-encode again, it is well possible that the resulting string is different, but syntactically the same.
In HTML, URL Encoding is sometimes interspersed with HTML Encoding. I.e., the ampersand is valid in HTML, but not in HTML. find.aspx?city=A&name=B becomes find.aspx?city=A&name=B in and HTML URL. However, browsers are lenient and will accept wrongly HTML-encoded strings.
Finally, a not on the browser: if you type in a space in a link, even inside an <a> tag, it will escape the space (or other character) for you. Likewise, it will nowadays show the odd characters (é, ï etc) in the address bar, but when it sends it over HTTP, the browser will correctly do the encoding for you.
Update: about anwering your question of needing a "definitive" reference or proof.
While I couldn't find any on the internet, I decided to look for it myself using Reflector. Going through the methods that set, for instance, the HttpRequest.QueryString, you quickly encounter the private method HttpRequest.FillInQueryStringCollection which then calls HttpValueCollection.FillfromEncodedBytes. Somewhat near the end of that method, HttpUtility.UrlDecode is called for the values. Conclusion: do not call it yourself, to prevent double decoding.
You can see this for yourself when you download Reflector and disassemble the .NET libs of System.Web.
For your example you can change this line
var url = "find.aspx?" + "location=" + encodeURIComponent( address );
to
var url = "find.aspx?" + "location=" + address;
and see the address as it is. Bu if address variable contains any '&' character your variable will be corrupt. So you are using encodeURIComponent to encode these things url.
On the Server side all these encoded strings are decoded back. It means encodeURIComponent is just for sending the address variable (whether it contains & character or not) to server side correctly.