I visited new GWT website and noticed that after clicking on tree items - link is changing without adding hash (for example, http://www.gwtproject.org/books.html). I know how to do url routing using hashes, but how URL routing is made in GWT website (and possibly can be made)?
Thanks in advance.
It's commonly called HTML5 PushState. A new way of dealing with the browser history by changing the URL without necessarily reloading the page. By listening on popstate events you can dynamically change your page just like using the hashtag method, with the benefit of having cleaner URLs and out of the box crawlability.
Have a look at the gwt website source. Internally uses the GQuery library (jQuery port for GWT) that leverages such pushState methodology.
EDIT: If you want to take benefit of pushState right from GWT (since it does not natively support it), you can also have a look at Johannes Barop's pushState project.
Related
The setup: I have a Blogger blog set up on a domain name as blog.mydomain.com. The main site site at mydomain.com is running Umbraco CMS.
The problem: I need to have the navigation from the CMS transported to Blogger somehow, so that making a change on the main website doesn't require the extra step of modifying the navigation inside Blogger.
Generating the navigation data on the CMS side in what ever format it needs to be (XML, unordered list, JSON, etc) is not a problem. The problem is getting the data from Umbraco to Blogger after it is generated.
I'm not yet willing to use Javascript, as this would seriously impair the website for users browsing without Javascript. (Too bad because AJAX would be a very workable solution.)
I've tossed around the idea of using an iFrame. How would this work for a navigation system including sub-menus? Creating and deleting multiple iframes is out of the picture, since I don't want to use Javascript. I could use one large iframe to allow for the sub-menus, but then it would cover content at the top of the content area, rendering it unclickable.
I'm thinking about how you could do this, but while I do - in this day-and-age javascript has become very common. Most users are going to have it, and those with it disabled really shouldn't be on the web. Is this the only reason you don't want to use javascript? Around 2% according to YDN have js disabled, and that's lower from other countries. As time goes on that 2% should get lower, I don't see that as an issue. However if you absolutely can't use javascript, I'll keep thinking. I might have an idea, I'll need to test it though.
It's not possible to use IFrame, cause of same origin policy. Both sites are on different domains, when user click menu item inside IFrame, there is no way to call parent window.
There are few ways how this can be done.
1) Javascript solution. Use json rpc, or another cross-domain calls. Load menu from your CMS and render it. Yes, this requires javsascript, but, seriously, show me the site, which does not use javascript.
2) Direct server communication.
Is it possible to perform http call from blogger ? If so, just perform http call to your CMS from Blogger, get data and render it.
3) Mixed flash/javascript solution. Flash can perform http call regardless of same origin policy. Get data with flash, use ExternalInterface to call Javascript function to render data.
There is no another way to do it. I suggest you to use javascript solution
You could build an HTML skeleton of empty ULs in Blogger (the max that you might need) to hold your navigation contents, and then link to an Umbraco-generated external stylesheet.
This stylesheet could fill those LIs with CSS generated content using the :before and :after pseudo-elements, and hiding unused LIs with CSS display: none.
An example of this is at: http://jsfiddle.net/5bXja/1/
This works in IE8+ so depending on your clients, this may-or-may-not be more widely supported than Javascript. Likely not. ;-)
So far what I have used with my gwt application is a simple FI, like #login, #welcome etc.
However I want to "refactor" my application in a more descriptive way, I need make it this way:
http://localhost:8080/main#login
http://localhost:8080/main#search
http://localhost:8080/profile#<username>
http://localhost:8080/api
etc.
Can I do this with GWT?
If you want to stay on the same GWT application, you'll have to use the HTML5 History API (pushState and onpopstate) instead of GWT's default History (or DefaultHistorian) implementation; which means your app would only work with browser supporting the HTML5 History API (or you'd have to provide a fallback).
This is possible with GWT, but if you don't know how to do it and/or how the HTML5 History API works, it'll cost you a lot (of time).
BTW, if you ever switch to the HTML5 History API, why keep some fragment identifiers?
The alternative is, as milan says, to split your app into smaller parts (/main, /profile, /api, etc.)
Yes, but /main and /profile are going to be separate (html) pages, so you'll have EntryPoint for each then (loading/unloading GWT modules). Is that want you want? Google's AdWords is an example (written in GWT), each tab is a separate HTML page (/dashboard/, /cm/CampaignMgmt, ...).
On the google website there an example of a simple GWT appliatoin, following is a link:
http://code.google.com/webtoolkit/doc/1.6/tutorial/create.html
The above application has a host page:StockWatcher.html
and StockWatcher.java is the entry point.
If I wanted to add more html pages to this application, we keep one single host page and the entry point will add different panels depending on which link the user clicked on? In this case, how to know which link the user clicked on? If I create a navigation panel and each link has a request parameter, then after the user clicks on the link, How to get the request parameter?
Are there any tutorials available online on how to create a fully functional application? The one example google provides is too simple.
Thanks so much in advance
You have two options to have multiple page web application using gwt.
1) Use gwt history feature and listen for the history change. In this approach at the initial page load itself browser downloads all the javascripts(Including the widgets which are not useful in current link). Still this can be avoided by using gwt code splitting.
2) Create multiple modules. In this case you have to create multiple html pages and GWT entry points. For each major functionality create a gwt module and link that with [modulename].html file. In this approach browser downloads only particular feature's javascript. Not all the javascripts.
Based on your application requirement you can pick one of the option. IMHO I would suggesst second option.
I want to design a website using GWT. This is my understanding of how GWT pages will be delivered to the client browser - When the user puts in the URL into her browser she receives all the static HTML + GWT javascript, and then the javascript queries the server for the dynamic page content and adds it to the DOM. eg - For a blog page the content of the blog is queried by the javascript. is my understanding correct?
If I know that the content will surely be a part of the page(add does not depend on user clicking an expand button etc.), Will it be more efficient if the blog content was a part of the HTML initially served? Something that could be done by using a templating engine like django.
Is there a way to make a templating mechanism in GWT?
Yes, putting your content into the HTML will reduce the number of round trips the client makes to your server. It also means that the blog content won't have to wait for your GWT javascript to load before it can be displayed.
GWT itself isn't useful for a template system, but most servers that run GWT servlets will also support JSP pages. GWT works fine with these pages, you just need to put the GWT script tag in as usual. You will no doubt be able to find a ready-made templating solution but rolling your own is not too hard.
I've just noticed that the long, convoluted Facebook URLs that we're used to now look like this:
http://www.facebook.com/example.profile#!/pages/Another-Page/123456789012345
As far as I can recall, earlier this year it was just a normal URL-fragment-like string (starting with #), without the exclamation mark. But now it's a shebang or hashbang (#!), which I've previously only seen in shell scripts and Perl scripts.
The new Twitter URLs now also feature the #! symbols. A Twitter profile URL, for example, now looks like this:
http://twitter.com/#!/BoltClock
Does #! now play some special role in URLs, like for a certain Ajax framework or something since the new Facebook and Twitter interfaces are now largely Ajaxified?
Would using this in my URLs benefit my Web application in any way?
This technique is now deprecated.
This used to tell Google how to index the page.
https://developers.google.com/webmasters/ajax-crawling/
This technique has mostly been supplanted by the ability to use the JavaScript History API that was introduced alongside HTML5. For a URL like www.example.com/ajax.html#!key=value, Google will check the URL www.example.com/ajax.html?_escaped_fragment_=key=value to fetch a non-AJAX version of the contents.
The octothorpe/number-sign/hashmark has a special significance in an URL, it normally identifies the name of a section of a document. The precise term is that the text following the hash is the anchor portion of an URL. If you use Wikipedia, you will see that most pages have a table of contents and you can jump to sections within the document with an anchor, such as:
https://en.wikipedia.org/wiki/Alan_Turing#Early_computers_and_the_Turing_test
https://en.wikipedia.org/wiki/Alan_Turing identifies the page and Early_computers_and_the_Turing_test is the anchor. The reason that Facebook and other Javascript-driven applications (like my own Wood & Stones) use anchors is that they want to make pages bookmarkable (as suggested by a comment on that answer) or support the back button without reloading the entire page from the server.
In order to support bookmarking and the back button, you need to change the URL. However, if you change the page portion (with something like window.location = 'http://raganwald.com';) to a different URL or without specifying an anchor, the browser will load the entire page from the URL. Try this in Firebug or Safari's Javascript console. Load http://minimal-github.gilesb.com/raganwald. Now in the Javascript console, type:
window.location = 'http://minimal-github.gilesb.com/raganwald';
You will see the page refresh from the server. Now type:
window.location = 'http://minimal-github.gilesb.com/raganwald#try_this';
Aha! No page refresh! Type:
window.location = 'http://minimal-github.gilesb.com/raganwald#and_this';
Still no refresh. Use the back button to see that these URLs are in the browser history. The browser notices that we are on the same page but just changing the anchor, so it doesn't reload. Thanks to this behaviour, we can have a single Javascript application that appears to the browser to be on one 'page' but to have many bookmarkable sections that respect the back button. The application must change the anchor when a user enters different 'states', and likewise if a user uses the back button or a bookmark or a link to load the application with an anchor included, the application must restore the appropriate state.
So there you have it: Anchors provide Javascript programmers with a mechanism for making bookmarkable, indexable, and back-button-friendly applications. This technique has a name: It is a Single Page Interface.
p.s. There is a fourth benefit to this technique: Loading page content through AJAX and then injecting it into the current DOM can be much faster than loading a new page. In addition to the speed increase, further tricks like loading certain portions in the background can be performed under the programmer's control.
p.p.s. Given all of that, the 'bang' or exclamation mark is a further hint to Google's web crawler that the exact same page can be loaded from the server at a slightly different URL. See Ajax Crawling. Another technique is to make each link point to a server-accessible URL and then use unobtrusive Javascript to change it into an SPI with an anchor.
Here's the key link again: The Single Page Interface Manifesto
First of all: I'm the author of the The Single Page Interface Manifesto cited by raganwald
As raganwald has explained very well, the most important aspect of the Single Page Interface (SPI) approach used in FaceBook and Twitter is the use of hash # in URLs
The character ! is added only for Google purposes, this notation is a Google "standard" for crawling web sites intensive on AJAX (in the extreme Single Page Interface web sites). When Google's crawler finds an URL with #! it knows that an alternative conventional URL exists providing the same page "state" but in this case on load time.
In spite of #! combination is very interesting for SEO, is only supported by Google (as far I know), with some JavaScript tricks you can build SPI web sites SEO compatible for any web crawler (Yahoo, Bing...).
The SPI Manifesto and demos do not use Google's format of ! in hashes, this notation could be easily added and SPI crawling could be even easier (UPDATE: now ! notation is used and remains compatible with other search engines).
Take a look to this tutorial, is an example of a simple ItsNat SPI site but you can pick some ideas for other frameworks, this example is SEO compatible for any web crawler.
The hard problem is to generate any (or selected) "AJAX page state" as plain HTML for SEO, in ItsNat is very easy and automatic, the same site is in the same time SPI or page based for SEO (or when JavaScript is disabled for accessibility). With other web frameworks you can ever follow the double site approach, one site is SPI based and another page based for SEO, for instance Twitter uses this "double site" technique.
I would be very careful if you are considering adopting this hashbang convention.
Once you hashbang, you can’t go back. This is probably the stickiest issue. Ben’s post put forward the point that when pushState is more widely adopted then we can leave hashbangs behind and return to traditional URLs. Well, fact is, you can’t. Earlier I stated that URLs are forever, they get indexed and archived and generally kept around. To add to that, cool URLs don’t change. We don’t want to disconnect ourselves from all the valuable links to our content. If you’ve implemented hashbang URLs at any point then want to change them without breaking links the only way you can do it is by running some JavaScript on the root document of your domain. Forever. It’s in no way temporary, you are stuck with it.
You really want to use pushState instead of hashbangs, because making your URLs ugly and possibly broken -- forever -- is a colossal and permanent downside to hashbangs.
To have a good follow-up about all this, Twitter - one of the pioneers of hashbang URL's and single-page-interface - admitted that the hashbang system was slow in the long run and that they have actually started reversing the decision and returning to old-school links.
Article about this is here.
I always assumed the ! just indicated that the hash fragment that followed corresponded to a URL, with ! taking the place of the site root or domain. It could be anything, in theory, but it seems the Google AJAX Crawling API likes it this way.
The hash, of course, just indicates that no real page reload is occurring, so yes, it’s for AJAX purposes. Edit: Raganwald does a lovely job explaining this in more detail.