Sagar Ganatra's Blog

I’ve always liked the Virtual File System (VFS) implementation in ColdFusion, but I always griped about one thing. The files written to the VFS are available at the Server level and are not specific to an application. However, ColdFusion 10 now includes support for Application specific in-memory file system. This means that, if you write a file to the virtual file system, only those files in the same application can access it. If an attempt is made by another application to access this file, the server would happily throw an error.

I’ve been playing with the WebSocket feature introduced in ColdFusion 10 for some time now. I was trying out pushing images over a ColdFusion WebSocket channel and it worked just fine. But this time I wanted to put WebSockets to test and wanted to push large data at regular intervals. I thought maybe I can push video data over WebSockets and it turned out that there is no direct way to stream video data to many clients. I came across the function - drawImage that can be used to draw an Image or Video on a HTML5 Canvas. Once an image is drawn on the Canvas, it’s base64 encoded data can be obtained by calling the toDataURL function on the Canvas object.  This data can then be transferred over a ColdFusion WebSocket to all subscribers who can then use this  data to draw the image(video frame) on a Canvas.

This week I started to learn jQueryMobile and was going through the online documentation that explained the basics. While I was trying out the sample examples, I came across an issue that I thought I’ll share with you. I had posted this on the jQueryMobile forum but I didn’t receive any solution to this. The issue here is when you have two anchor elements with its ‘href’ attribute pointing to the same div (#child data-role=”page”) with one marked as a button and the other marked as a popup dialog, then which ever button you choose first its action will be applied to the other button as well. Say if you click the second button that shows the dialog box containing the page it works fine, but now when you click the first button it shows the dialog box instead of showing it as a page. This is how it works the other way too i.e. if you click the first button the page is shown (as expected), but on clicking the second button it shows the page instead of displaying it as a dialog box.

Today I was reading about CSS3 and I stumbled upon CSS3 regions . I was completely flabbergasted with what I saw and learnt today. Imagine that you’re trying to build a website for a magazine containing multiple columns (say 3). It would be arduous to fix the textual content on a particular column and then move the rest of the text to other columns. Now with Content Flow mechanism, the extra content can be moved to other columns in the layout with ease. There are just a couple of properties that you need to define in the styling sheet and you’re done. But this is not it. When you resize the browser window, the content automatically flows to other regions depending on the browser size.

The for-in loop construct in ColdFusion is generally used to loop over a structure variable. In ColdFusion 10, one can use the same for-in construct to loop over Query and List variables. Here is an example in which the for-in construct is used to loop over Query and List variables.

Yesterday Ben Nadel asked me a question on Twitter, on using filterCriteria when publishing a message on a web socket channel from server side. The method ‘wspublish’ allows you to perform a server side push to a client who has subscribed to a channel. It takes three parameters – channelName, message and filterCriteria. I always assumed that the values present in subscriberInfo and publisherInfo can be compared in Channel Listener functions (canSendMessage, beforePublish etc) before the message can be received by the client. Although this technique is available, what I found after having a discussion with a fellow developer ( Awdhesh ), is that I can specify simple conditions when subscribing or publishing.

In REST everything is treated as a resource and each resource is associated with a URI from which it can be accessed. As mentioned in my series of posts on REST ; in ColdFusion methods defined in a CFC are made RESTful by adding the attributes httpmethod and restpath. The restpath value specified in the method can then be used to access the resource. Although this would serve the given purpose, it would be a good idea to have a root resource resolve a generic URL and then have different methods that resolve other path of the URL.

I was looking into ways in which users can be authenticated before they start to receive or send messages over a WebSocket channel in ColdFusion. I found that there are two ways in which this can be done. The first approach is to call the ' authenticate'  method on the socket object. The other way is to use cflogin to authenticate the user. The authentication level can be taken a step further in various channel listener functions. By implementing these listener functions, some sort business logic can be devised wherein the logged in user with certain credentials can be allowed to subscribe or publish to a channel.

The HTML5 Web Sockets represent the next evolution of web communications. A WebSocket is a full duplex, bidirectional communication channel that operates over a single TCP socket. It has become a standard for building real time web applications. In ColdFusion 10, a messaging layer has been provided that implements the Web Socket protocol. It enables you to build applications that are based on publisher/subscriber model and applications that are based on subscriber model wherein a push from a server is possible.

A very quick post on disabling timeout for the requests. You can now set the requesttimeout to zero in cfsetting tag i.e. <cfsetting requesttimeout=0>

I was working on creating a CRUD application with REST and wanted to retrieve records with a GET request. The GET request would contain the ARTID for which the record has to be retrieved in the URL itself. To do this I had added an argument to the method implementing the GET request with ‘restargsource’ attribute set to path. The URL would be of the form: http://localhost:8500/rest/restapp/artService/getart/1 However, in another scenario I wanted to retrieve all the records from the ART table when there is no ARTID specified in the URI i.e. with the URL: http://localhost:8500/rest/restapp/artService/getart/ PathParams are always required and if they’re not specified then a ‘404 Not found’ error would be thrown. I thought of adding another method to handle this GET request with no PathParams. But, it would have made my code look clumsy and semantically not correct. However, I was able resolve this by providing a regular expression for the PathParam argument.

A quick post on the new function arraySlice added to the list of functions in ColdFusion 10. The arraySlice function is used to  select a part of the array. It takes three arguments – array, offset and length.

In ColdFusion 10, one can restrict the type of file being uploaded to the server when using CFFILE to upload the files. The new attribute accept allows the user to specify various MIME types or extensions of the file that can be accepted by the server. If the user tries to upload a file with a .txt extension but it contains xml data (application/xml MIME type) then the server would accept or throw an exception based on the value specified for the strict attribute. 'strict' is a boolean attribute added to the CFFILE tag. By default it is true and therefore wouldn't allow the user to upload a file whose contents are of different MIME type. When the strict attribute is set to false it would allow the user to upload a file irrespective of its content. However, an error would be thrown if the extension of the file doesn't match the ones specified in the accept attribute.

There are a couple of variables that have been introduced in Application.cfc which are REST specific. These are this.restsettings.cfclocation and this.restsettings.skipCFCWithError . If you have a list of directories containing REST enabled CFCs then you can specify the same in the variable this.restsettings.cfclocation. At the time of registration, the specified directories and its subdirectories will be scanned for REST enabled CFCs and then deployed. If any of these CFCs contain compilation errors then an error is thrown and the registration would fail. To tackle this another variable this.restsettings.skipCFCWithError is provided. When set to true, the CFCs with compilation errors would be skipped. Only those without any compilation errors would be deployed successfully.

Today, I wrote a post on the new lifecycle method - ‘onAbort’, which can be defined in an Applicaiton.cfc file . It is invoked when the cfabort tag is executed. David Boyer , asked me whether the onRequestEnd method is also invoked on executing the cfabort tag. In CF 9.0.1 it did invoke the onRequestEnd method. See Ben’s post: http://www.bennadel.com/blog/2221-CFAbort-And-OnRequestEnd-Behavior-In-ColdFusion-8-And-ColdFusion-9.htm Now in CF 10, this behavior has changed. The onRequestEnd method is no longer invoked when cfabort, cflocation or cfcontent tag is executed. The onAbort handler method defined in Application.cfc file would be invoked on executing these tags. Also, the onRequestEnd method would not be invoked even if the abort handler(onAbort) is not defined in Application.cfc.

I was experimenting with a new method 'onAbort' introduced in ColdFuion 10 which can be defined in an Application.cfc file. This method is invoked when cfabort is called. What if showerror attribute is also present in the cfabort tag? Would it still invoke the onAbort method and then onError? The onAbort method would be ignored and the onError method would be invoked. Even in a case wherein the onError method is not defined in Application.cfc, the onAbort method wouldn't be invoked. In this case the error message would be shown on the standard error template.

There are various complex types in ColdFusion – Array, Struct, Query. When a REST service in ColdFusion returns one of these complex types, it has to be serialized to either JSON or XML format. As explained in my previous post , the HTTP protocol can be used in content type negotiation. You can specify the desired content type either by specifying it at the end of the URL or in the Accept header of HTTP request. In this post, I’ll explain the format in which the complex types are returned from a ColdFusion REST service.

Prior to ColdFusion 10, to write or append to a file one had to specify the file content in the output attribute of CFFILE tag. In ColdFusion 10, you can specify the file content in the body of the cffile tag. In cases where the file content is specified in body as well as in the output attribute, the output attribute would be ignored.

In ColdFusion 10, you can now show the users location on a Google map created with the CFMAP tag. The CFMAP and CFMAPITEM tags now have a boolean attribute showuser . When set to true the browser would ask for the users permission and then display users geo-location on the map. This is now supported in most of the modern browsers. In cases where the browser doesn’t support Geo-location API then the values provided in centeraddress or centerlatitude\centerlongitude attributes will be used to add a marker in the Google map.

Following with my previous post on how content negotiation between the client and server help in invoking an appropriate REST service. In this post I’ll explain how one can specify multiple mime types in the request header and also the quality factor that enables server to decide which mime type to serve for the incoming request. The client sends a HTTP request to the Server along with several headers, one of them is the Accept header. The Accept header can contain a list of mime types that the client (user agent) is willing to process. These mime types are separated by a comma and may optionally be combined with the quality factor. A CFC can contain several methods with produces attribute set to a specific mime type. The Accept header may contain several mime types: text/html, text/plain, application/xml, application/json, */* Server would parse the Accept header and will search for a REST service that matches the mime type specified first in the Accept header list. In this cas

The HTTP protocol provides a Content negotiation mechanism using which different formats of the document can be served using the same URI. For example, a JavaScript application can request the content in JSON format and an external system say a Java client can request for the same content in XML format. Here the clients need to specify the content format in the Accept attribute of the HTTP request. The REST service can specify the format in which the data will be returned to the client in ‘produces’ attribute.

As mentioned in my earlier post there are various ways in which data can passed to a REST service. The cfargument tag has a new attribute restargsource, it can take one of these values – path, query, matrix, form, cookie and header.

In my previous post, I’d explained how REST services can be created, published and accessed in ColdFusion 10 . Andy , asked me “Is there any way to avoid having the /rest/restapp/ in the URL?”. In short Yes. ‘rest’ in the URL lets the ColdFusion Server know that the incoming request is for a REST service. As mentioned in my previous post, you can update the servlet mapping defined in web.xml located at cfusion_home\wwwroot\WEB-INF directory. But it can't be avoided. Coming to the ‘restapp’ in the URL which indicates the Application name or the Servlet mapping. It can be removed from the URL by placing the CFCs in a default directory. While registering a REST service in the ColdFusion Administrator, there is an option to set the service as a default service, meaning all the CFCs placed in the directory would not require the Application name or Service mapping to be provided in the URL.

In ColdFusion 10, support for creating and publishing REST services has been added. The ColdFusion components can now be made available as REST services and these services can be consumed by various clients. REST stands for Representational State Transfer. It is an architectural style which is based on web standards and HTTP protocol. The idea here is to use HTTP protocol instead of complex mechanisms such as CORBA, RPC or SOAP to connect between the machines. In fact, the World Wide Web which is based on HTTP can be viewed as a REST based architecture.

The queryNew() and queryAddRow() functions are used to create a query data structure and add empty rows to it. To add record sets to the query, function querySetCell() is used. If there are say three columns and you want to add say five rows to the query, then you would have about sixteen lines of code. That's huge and it will increase with number of columns and the number of records that you want to add. In ColdFusion 10 there's a third parameter introduced in queryNew() and queryAddRow() functions. The third parameter can accept either a struct,  an array of structs. Ray Camden had covered this in one of his POTW posts. One feedback that came from one of the ColdFusion users is to use an array or a two dimensional array to initialize or add rows to the query. This has now been implemented and is available in the public beta release. Here’s how it works:

The arrayAppend function in ColdFusion is used to append an element to the end of the array. Now in ColdFusion 10, it is possible to concatenate two arrays using the same arrayAppend function. A third parameter of type boolean is added to the function; when it is set to true the two arrays are concatenated.

After more than 20 months of research, planning, development and keeping  you all in suspense about the next version of ColdFusion, code named  Zeus; I'm finally proud to announce the release of the public beta version of none else than ColdFusion Zeus. You are free to download it here and report bugs here . This release comes with tonnes of new features and enhancements. It not only focuses on HTML5 features but also provides rich features such as RESTful WebServices, Closures, Java Integration, Security enhancements and many more. I wanted to create a picture that depicted all the new features in ColdFusion 10, like I did when public beta of  CFBuilder 2 was released. But I couldn't since its a massive release and capturing everything in one single picture was not possible at all. However, I managed to create an app (like a movie clip) and hence the title 'Now Showing - ColdFusion Zeus'. You can access the app here . Click on the chapters and learn what's

Today, one of the ColdFusion users asked me a question "Is there anyway I can find out whether a path is a directory or a file? There is no isDirectory() function available in ColdFusion and I don't want to write Java code to do this. Any help?" For a moment I thought really! is there no way that ColdFusion can tell you whether a given path is of a directory or file? But sooner, I came across the function 'getFileInfo' which takes the path as an argument and returns a struct data that contains various metadata properties of the file. The struct includes a key - 'type' whose value can either be a directory or file. The below code shows how you can determine whether the given path is of a directory or file:

I know it's been more than 15 days since the world celebrated new year and every one made some big and small resolutions which they hope they will live up to in this year. I had a fair 2011; there were a few ups and downs but in the end its gone and 2012 is here. Last year I presented ColdFusion Builder 2 at SOTR on the very day it was released to the public (how exciting!!). I was very much excited and nervous at the same time since this was my first talk at a conference. Nevertheless it went well, I have said this before and will say it again, 'Edinburgh is beautiful'.

To measure the time taken for a page to load one can use the Date object in the head section and calculate the time taken for the page to load in window.onload function. However, it calculates the time taken for the page to load after the first bit of JavaScript in the head is executed. This doesn't indicate the time taken by the web server to serve the requested page. The Navigation Timing API introduced in HTML5 provides data that can be used to measure the performance of a website. The API provides a PerformanceTiming interface which contains several attributes that can be used to get end-to-end latency data.

Today I stumbled upon the PageVisibility API introduced in HTML5, which gives developers an opportunity to improve the performance of a web page and to better the user experience. Whenever a user opens a new tab or navigates to another tab, the behavior of the current page from which user navigated can be controlled using this API. Consider a webmail client that is trying to look for new mails every two seconds, if a user opens a new tab or minimizes the browser window then retrieving mails every two seconds would expend resources, whilst the user is not actively viewing the page. Here the PageVisibilty API would come handy and would allow developers to alter the behavior of the web page.

I came across a publisher\subscriber protocol called PubSubHubBub. It is a server-to-server web-hook-based pubsub (publish/subscribe) protocol - an extension to Atom and RSS. Here the parties (servers) get an instant notification when a feed URL, that  they are interested in is updated. Traditionally a subscriber would subscribe to a feed and poll for it at regular intervals, to see if there is an updated feed available. In this protocol rather than polling for a feed, the content is pushed out from the publisher. The theory here is that the subscriber can subscribe to a feed via a 'Hub', which then would inform the subscribers when the feed is updated. How PubSubHubBub works? A Publisher instead of sending an update to every subscriber, it includes a in its feed URL and sends an update to the Hub . A Subscriber sends a subscription request to the Hub with the feed URL that it is interested in. The request also contains a callback URL to which the Hub should send an up

Today when I woke up and switched on the Television to see what's making the news; I heard about Steve Jobs death. For the first time in my life, I'm feeling very sorry for a tech giant who passed away. Steve was an extraordinary human being. He kissed success not just once but many times. He changed the way we experience technology. His charisma, passion and more importantly desperation to do something great is matchless.

One of the key aspects of building web applications that deliver great user experience is to build applications that are highly responsive. Browser vendors are trying to improve the speed of their JavaScript engines and are enabling the web applications to perform well. Since JavaScript was introduced, there has been no way to execute the code outside of the browser UI thread i.e. it has remained single threaded. The Web Workers API introduced in HTML5 enables web applications to run scripts in the background, independent of the UI thread. The performance of a web application can be greatly improved by using Web Workers since each worker would spawn its own thread. These threads can be used to perform computationally intensive tasks in the background without affecting the performance of the entire application.

In ColdFusion, CFPDF tag can be used to perform several PDF related operations such as adding a watermark, generating thumbnails, deleting pages, merging documents and securing a PDF with password. Today I wanted to merge all my bank statements into a single PDF document, such that only the first page from each document containing the summary of the statement is present in the merged document.

Today I was looking into web storage (localStorage) feature introduced in HTML5. Most of the modern browsers provide means through which key/value pairs can be securely stored and retrieved for later use. Browser cookies can indeed be used for the storage of persistent data but are limited in capacity. Also with cookies, the data is transmitted in every HTTP request thereby making the web applications run slow. Unlike cookies, in local storage there is no limit on the size of the data and it is never transmitted to the web server unless an attempt is made to send it manually. Whenever the data in the storage area changes a ' storage ' event is fired. This event is fired whenever the methods setItem(), removeItem(), or clear() are called on the localStorage object. However, when I tried to use these methods to update the localStorage area, the storage event never fired: The methods setItem and clear did change the storage area and I confirmed this by referring to the resour

Yesterday at the ColdFusion Developer Week, I had demonstrated the Productivity features in ColdFusion Builder. Here is a cloud of these features: 

The Adobe ColdFusion Developer Week is here and is scheduled from 12th of September to 16th of September 2011. I'm pleased to announce that I'll be speaking on Wednesday, 14th of September and my session title is 'ColdFusion Builder: The Professional IDE to Boost Your Productivity' . This session would focus on how you can get started with using ColdFusion Builder and productivity features that would enable you to develop ColdFusion applications in no time. I'll also be demonstrating the new features that have been introduced in ColdFusion Builder 2.0. You can register for the session here -  http://www.adobe.com/cfusion/event/index.cfm?event=detail&id=1489920&loc=en_us

The Canvas element introduced in HTML5 is the most talked about feature in HTML5. It allows a developer to draw on a rectangular area and the ability to control each pixel in it. I'm not a very big fan of powerful graphics and animation on the web, however I wanted to try Canvas in conjunction with another popular feature - Web Sockets. The idea is to use the mouse events to draw on the Canvas and then send the coordinates to remote clients using Web Sockets. I have used the pusherapp Web Socket library in my example and this video shows how two clients can play a Tic-Tac-Toe game: Unable to display content. Adobe Flash is required. As you can see in this video, the mouse movements made on the canvas will draw lines on it and also cause lines to be drawn on another browser window.

Google announced the Places API recently at Google I/O (2011) and I was looking into this, to see how this API can be used in conjunction with ColdFusion maps created with CFMAP. The Places API can be used to retrieve place information which includes: Places of interests such as parks, restaurants, hospitals which are nearby to the users location. More detailed information on the place, such as the address, phone number etc,. The API can also be used to perform check-in at a particular place and to add\delete a place. These check-ins can then be used to evaluate the popularity of the place. In this post I'll explain how to retrieve the places of interests and displaying the same on a ColdFusion map using CFMAP.

HTML5 has introduced several input types such as EMAIL, URL, RANGE, SEARCH, DATE, TIME, etc,. Most of the modern browsers have implemented them and are ready to be used in a HTML document. Another exciting feature introduced in HTML5 is the form validation. Instead of writing JavaScript to validate users input, browsers can now validate it and show an appropriate message if the validation fails. The validation message is shown in line with the field for which the validation has failed. The default error message is shown when the validation fails. In this post I'll explain how these error messages can be changed.

The other day I had posted on uploading a file using XmlHttpRequest 2 and tracking the progress of the file upload process using the progress event on XHR2 object and the progress tag. Another enhancement added to the XHR2 specification is the introduction of FormData object. Using the FormData object, one can create a set of key-value pairs and send them as form data in a XHR request. The FormData object is passed in the send() method of the XHR object:

The Editor is the most important feature in an IDE and the code assist features in the Editor helps in developing applications quickly and hence help in increasing the productivity. One of features is the 'auto insertion of tag attributes'. Most of the tags in ColdFusion have a mandatory attribute, for example the attribute 'name' is mandatory when using the cffunction tag. In ColdFusion Builder 2, these attributes are auto inserted i.e. when a user types in the cffunction tag and invokes code assist (using CTRL + SPACE) the name attribute is auto inserted. auto insertion also works for function arguments wherein the required arguments are auto inserted. Auto Insertion of Tag attributes As explained above, the mandatory attributes are auto inserted whenever the code assist is invoked for tags such as cffunction : In the above picture, code assist for cffunction is invoked and the tag is selected from the list. This would auto insert the required attribute 'name'

I had blogged about JavaScript debugging with Chrome Developer Tools  some time back, wherein I have explained how these developer tools can help in debugging javascript code. Today Google Chrome 12 was released and my Chrome browser was updated to this version. As with every release, there have been some improvements made on performance, usability etc,. One feature that stood out for me is the ability to De-obfuscate the javascript code. What is Minification? Minification is the process of removing unnecessary characters such as white spaces, comments, new lines from the source code. These otherwise would be added to make the code more readable. Minifying the source code helps in reducing the file size and thereby reducing the time taken to download the file. This is the reason why most of the popular javascript libraries such as jQuery are minified. A minified jQuery file is of 31 KB in size where as an uncompressed one is about 229 KB. Unfortunately, debugging minified javascript f

I was working on an online\offline application, wherein I wanted to display a set of records stored in the local database to the user when he goes offline. The only way to determine the network status is to send a XHR request to the server at particular time intervals (polling). If the server responds back with some data it is understood that the user is online. However, I came across two event listeners 'ononline' and 'onoffline' which are triggered when the network status changes.

HTML5 has introduced several semantic tags such as HEADER, FOOTER, SECTION, ARTICLE, ASIDE, NAV etc,. The rationale behind creating these structural tags is to divide the web pages into logical parts with tags that are descriptive of the type of content they contain. Before HTML5 the div tags were used in creating blocks of content in a HTML document. Recently, I was having a conversation with one of my team members from whom I learnt that the CFDIV tag can be used to output these semantic tags. The CFDIV tag has an attribute  'tagname' . This attribute can be used to specify the HTML container tag i.e. one can specify tagname="header" to output the header tag. Similarly the tagname attribute can be used to specify other HTML5 semantic tags. Why should I use CFDIV tag to output the semantic tags? Well, this is an obvious question you are likely to ask yourself before you write the CFDIV tag. It is not so obvious to one who uses CFDIV tag in their day to day de

I was looking into the Google Maps API the other day and came across some APIs which are really cool. I came up with a use case to show path from the current location to a particular destination entered by the user. I was also trying to achieve that Indiana Jones like effect on the map i.e. to show an animation of the path being drawn on the map. The idea here is to show the moving path until the destination is reached and also to pan the map accordingly. Unable to display content. Adobe Flash is required. As seen in the video, a marker is added to the map specifying my current location (Bangalore, India). The current location data is retrieved using the HTML5’s Geolocation API. Once the latitude and longitude information are available, a marker can be added to the map. You can now enter one of your favorite destinations in the text box provided and click the Submit button to see a path drawn from your current location to the destination. The path is drawn using the Google map