Overcoming the Cookie Size Limit When Using jQuery DataTables and Saved State

One of the features of the jQuery DataTables plugin is that you can use the configuration option "bStateSave" to store the current view of the table (the sort order, the number of rows displayed, the filter term, etc.) in a cookie, so if the user navigates away from the page then comes back, the table view is the same as how they left it.

However, if your website or web application stores the state of several DataTables, and a user hits all those tables faster than those cookies can expire (their default lifespan is 2 hours but can be customized with the "iCookieDuration" option), the user could hit the browser cookie size limit and start seeing errors on your site.  I ran into this problem today with an application I've been working on.

Fortunately, starting with version 1.9, DataTables provides functions that let developers intercept the process of saving the table state and reloading that state, and the plugin author provides a documentation page on how to use those functions to store the state data in localStorage, which in most browsers allows you to store a few MBs of data per site (far more than the 4K limit per site for cookies):

http://datatables.net/blog/localStorage_for_state_saving

In my case, I decided that I would store the state data in sessionStorage rather than localStorage, but the principle was the same.

Adding Oracle Support to BugLogHQ: How the Application Design Made it Easy

As I mentioned in my previous blog post, in order to try out BugLogHQ in my work environment, I knew I would have to update the code so it could run against Oracle database tables.  So I started looking through the code to see how difficult of a task that would be, to see if it was worth the trouble.  Changing the code to support another database would mean at least looking at (if not updating) every block of code that performed a SQL operation:  if there were a lot of such blocks, it could be a time-consuming task.

Fortunately for me, BugLogHQ was designed to abtract most of the SQL operations behind a DAO layer.  Each database table used by BugLogHQ is mapped to a DAO CFC in the components/db folder of the BugLogHQ application, and those CFCs spell out the name and cfqueryparam data type for each table field and inherit getter and setter-type functions from a base DAO class.  When it comes time to persist data from instantiated DAO objects into the database, the DAOs are processed by the dbDataProvider.cfc in the components/lib/dao/ folder, and that CFC contains the SQL code for performing all of the CRUD operations.

(I should point out that this is a somewhat simplified description of all of the "moving parts" involved in data persistence in BugLogHQ, but after following the code through the process of adding and removing records I determined that I didn't need to make changes to other objects such as the DAO factory).

The main issue I needed to address was the fact that the current code for inserting a new record took advantage of the autoincrement feature in the other databases supported by BugLogHQ (MySQL, MS SQL, etc.).  Oracle doesn't come with an autoincrement field option.  Instead, Oracle has what are called sequences, which are essentially autoincrementing numbers that exist separately from the database tables (meaning you could, if you wanted to, pull the next integer from a particular sequence into any table).  So in the SQL install script I wrote to create the needed tables in Oracle (mirroring the install scripts for the other database engines present in the BugLogHQ install folder), I added lines to create sequences for each table, with each sequence name being the table name with "_seq" appended to the end of it.  I then added code to the _insert() function in the dbDataProvider.cfc to use the sequences for the primary key value when inserting a record:

  
<cffunction name="_insert" access="private" returntype="any">
  <cfargument name="columns" required="true" type="struct">
  <cfargument name="_mapTableInfo" type="struct" required="true">
  ...  
  <cfset var dbtype = variables.oConfigBean.getDBType()>
  <cfset var lstFields = structKeyList(arguments.columns)>
  <cfset var tableName = arguments._mapTableInfo.tableName>
  <cfset var seqName= tableName & "_seq">
  <cfset var pkeyName= arguments._mapTableInfo.PKName>
  ...
  <cfif dbtype eq "oracle">
    <cftransaction>	
      <cfquery name="qry" datasource="#DSN#" username="#username#" password="#password#">
        INSERT INTO #getSafeTableName(tableName)# (#pkeyName#,#lstFields#)
        VALUES (
        #seqName#.nextVal,
        <cfloop list="#lstFields#" index="col">
          <cfqueryparam cfsqltype="#arguments.columns[col].cfsqltype#" value="#arguments.columns[col].value#" null="#arguments.columns[col].isNull#">
          <cfif i neq listLen(lstFields)>,</cfif>
            <cfset i = i + 1>
          </cfloop>
        )
      </cfquery>
				
      <cfquery name="qry" datasource="#DSN#" username="#username#" password="#password#" result="qryInfo">
        select #seqName#.currVal as lastId from dual
      </cfquery>
    </cftransaction>
    <cfset newID = qry.lastID>
  <cfelse>
  ...

So if the dbtype value (which comes from the config/buglog-config.xml.cfm file) is "oracle", the Oracle insert code block will execute. The first cfquery block will insert the record, using the nextVal() function of the sequence associated with the table to get the next value of the sequence, while the second cfquery block retrieves the current/latest value of the sequence via Oracle's DUAL "table" (a construct designed to perform pretty much any utility operation that returns a single record or value).

The other issue I needed to address was adjusting some of the field data types.  Oracle's "varchar2" data type can only hold 4,000 characters of text; to store larger amounts of text, you need to use fields with the CLOB data type.  And in order to use cfqueryparam with such fields, you need to set the cfsqltype parameter of cfqueryparam to "cf_sql_clob".  So I updated the code in the entryDAO and extensionDAO CFCs to handle that (with the entryDAO.cfc code shown below):

<cfif variables.oDataProvider.getConfig().getDBType() EQ "oracle">
  <cfset addColumn("exceptionDetails", "cf_sql_clob")>
  <cfset addColumn("HTMLReport", "cf_sql_clob")>
<cfelse>
  <cfset addColumn("exceptionDetails", "cf_sql_varchar")>
  <cfset addColumn("HTMLReport", "cf_sql_varchar")>
</cfif>

After that, all that I had left to do was to add Oracle-specific conditional blocks to two other queries (ones that involved using database functions specific to each database platform) in two other files (components/hq/appService.cfc and components/lib/entryFinder.cfc), and I was done.

Had I done all of the changes I just described perfectly on the first try - which admittedly I didn't  :) - it would have taken me less time than it did to write this blog post.  And that's a mark of tight, well-designed application architecture, where certain key aspects of application behavior are centralized in a manner that lets you add functionality (in this case database engine support) by updating just a few files responsible for handling that particular task.

Need A CF App for Tracking Errors From Multiple Applications? Check Out BugLogHQ

Last month, during a brief lull in my work projects, I decided to tackle an issue I'd been putting off for awhile:  finding a better way of managing errors caught and reported by my ColdFusion applications.  All of my apps are designed to email me a full report of any errors that reach the global error handler, and while that means I'm immediately notified if there's a problem I need to address, the error message folder in my email account ends up serving as a de-facto error archive.  And now that we're (slowly) moving towards building applications as a team, it makes sense to have the errors stored in a centralized location.

After doing a bit of research, I ended up at the home page for the open-source bug logger BugLogHQ, created by Oscar Arevalo.  Based on the project changelog list, it sounded like it might have the features I wanted, but there wasn't a lot of explanatory documentation on the site and the screenshot images were thumbnails that couldn't be enlarged.  And it didn't support Oracle, which is our primary database engine at work (and a perusal of the Google Groups forum for BugLogHQ confirmed that).

Despite those factors, I decided it was worth trying to add Oracle support to the codebase so I could run it and try it out.  I'm glad I did:  BugLogHQ is a well-designed, robust application for managing errors in a way that will still let me keep track of what's happening with my apps.  Now that I've seen how it operates and what it can do, I'm kind of surprised that I had to do research to come across it:  either it completely slipped under my radar or it needs more publicity/exposure in the community.

Several things I like about BugLogHQ:

• I like the fact that it's easy to get up and running.  Download the files, put them in a "buglog" directory under the webroot (or use a mapping), run the SQL install script for your database of choice (mySQL, PostgreSQL, MS SQL 2000/2005, MS Access, and now Oracle) update the config file with your datasource name and database engine, and simply point your web browser to that "buglog" directory.  After logging in (which forces you to change the default password for the built-in admin user account), you can verify everything's working by going into the settings area of the app and running the tests, which all mimic the methods your other applications (referred to in BugLog parlance as "client" apps) can use to transmit errors to BugLogHQ.  Simple and straightforward.

• Just like most email clients have rules for filtering and acting on incoming email messages, BugLogHQ provides some rules for managing the errors that come in.  You can set up multiple "mailAlert" rules that will forward on particular errors (filtered by error type/severity, the source app's hostname or application name, or keywords in the configured error message text) to an email address of your choosing, or you can create a mailRelay rule that relays every error received to an email address.  And the emails sent out by BugLogHQ aren't just notifications about the errors:  they provide the full error details so you don't have to log into BugLogHQ to get more information.  There are also rules for discarding certain errors or for monitoring "heartbeat" transmissions from an app, so if the app is offline for a certain length of time BugLogHQ can report the problem.

• The methodology BugLog uses to report errors is very well-designed.  If your client app is also a CFML app, you simply instantiate a single CFC (with settings for interacting with the BugLogHQ web service you want to utilize) in either the application scope or a bean factory, then call it with its notification function whenever you want to send information to the BugLogHQ app.  If the client app is reporting an error, you can send BugLogHQ a line of message text, the error struct (the raw "cfcatch" struct), the type/severity of the error, and a struct of any additional information you want as part of the report (like the affected user's ID or name). Here's how I called it from the main.error() controller function in the FW/1 application I used during my testing (where I've instantiated the CFC as a service object):

  public void function error(rc) {
      var extraInfo= {username= session.user.getUsername()};
      variables.bugLogService.notifyService("Error report from TestApp1",request.exception,extraInfo,"INFO");
  }
  

  All of those parameters are optional, so you don't need an error struct if you're reporting something that's a status or informational message rather than an error.  If there's a problem with sending the report to BugLogHQ, it'll fallback to sending an email containing all that information to whatever address you specify so the error doesn't get lost.

• I also appreciate how BugLogHQ "eats its own dogfood".  If an error occurs in BugLogHQ itself, it'll record the error just like it would for any client app, and if the error occurs during the recording process it'll report the error via email.

• BugLogHQ utilizes a scheduled task (with a default interval of 2 minutes) referred to in the app as the "BugLog Listener Service" to denote and process incoming error messages.  When the task fires, the error messages that have been received since the last run of the task are processed and then written to the error database.  If there's a problem with writing to the database (which I understandably encountered as I was tweaking the code to support Oracle), it'll maintain the errors in the queue until the next iteration (and you can view the contents of the queue within the BugLogHQ dashboard).  Sometimes you need to restart that service in order for certain changes to take effect. If you somehow forget to reactivate the service, it'll be restarted when it receives a new error report from a client app.

• If one or more of your clients apps are NOT CFML-based web applications, there are library files provided that let you submit errors from PHP or Python apps, or straight from Javascript.  I haven't tried out those files yet, but we do have a few PHP apps in our shop now that could make use of the PHP option.

• There are configuration options for tying BugLogHQ to a JIRA instance, providing error summaries via RSS or a digest email, and setting an API key to ensure that only your apps can submit data to BugLogHQ.

Bottom line:  if you don't yet have an error-logging application or other mechanism for storing and managing errors from your application(s), you should take a look at BugLogHQ.  Oscar and his contributors have done a great job with this application.

dirtyFields jQuery Plugin Updated with New Options/Functions

I've made some updates to my dirtyFields jQuery plugin.  Here's the rundown:

• Added two new public functions:
  • getDirtyFieldNames() returns an array of all currently dirty fields.
  • updateFormState() checks the clean/dirty state of all form fields in the specified container
• Made two changes to how the CSS class denoting a dirty/changed form is applied:
  • Added a new configuration option ("self") to apply the class to the actual form element.
  • Split the single option for applying a style to a changed text input and select drop-down into two separate options for granular control (if you used the textboxSelectContext option with a previous version of the plugin, you will need to update your code).
• Added three new configuration options to control plugin behavior:
  • The denoteDirtyFields option controls whether or not the dirty CSS class is applied to the form elements that are dirty/changed.
  • The exclusionClass option specifies the name of the CSS class that, when applied to a form field, will exclude that field from being processed by the plugin.
  • The ignoreCaseClass option specifies the name of the CSS class that, when applied to a form field, will instruct the plugin to do a case-insensitive evaluation of the current and original states of the field.

All of these changes were implemented in response to code suggestions made a team of developers (listed in the GitHub readme.txt file) who modified the plugin to meet their specific needs in one of their intranet sites.

Quick ColdFusion Tip: Use ClearParams() When Doing SQL Inserts in a Loop

Today I had the need to write code that would loop over a recordset, parse the data in each iteration, and then insert the transformed data into another table.  Nothing I haven't done countless times, but this time I was using the query functions in cfscript to do my inserts.  I knew the resulting code was going to be a bit slow (as inserting thousands of rows takes time), but when I ran it it was a LOT slower than I expected.

After adding some code to time the various parts of my routine, I discovered that the time it took for each insert transaction was steadily growing with each iteration of the loop, to the point where it was taking 500+ milliseconds per insert.  But why?

Then I saw the problem.  I had forgotten to invoke the query object's clearParams() function at either the beginning or end of my loop.  Apparently ColdFusion will let you create a query parameter with the same name attribute using addParam() - as was happening in my loop - and not throw an error (which is what I would have expected to happen), but it leads to a performance issue with the SQL execution.

In the few times where I've reused a query object with different parameters, I've been careful to use clearParams(), but I simply overlooked it this time.  Lesson learned.

 

Adding a Time Selector to the jQuery UI Datepicker Widget

One of the functional requirements for the voter registration application I blogged about recently was that the application should not allow further registrations between the registration deadline (October 16 at 9pm) and a date after the election specified by the state Board of Elections.  For the initial run of the application, I simply hard-coded the deadline and restart date into the application logic, knowing full well I couldn't leave it that way unless I wanted to personally change the code year after year....which I don't.

So this week I set out to write a tool within the administrative interface of the application that would allow a non-programmer to update the deadline and restart date every year.  The jQuery UI Datepicker widget is my tool of choice when it comes to having users enter or edit a date, but I've used a few different approaches to having users enter a time of day.  This time around, I decided to see I if could find something comparable to the Datepicker widget for setting the time.

What I found was a rather sweet plugin called the Timepicker Addon that adds a set of time controls to the jQuery UI Datepicker.  If you customize your jQuery UI download to include both the Slider and Datepicker widgets, you can present the time controls as sliders, like so (without the Slider widget, you get select boxes):

The plugin comes with a number of configuration settings so you can do things like adjust the time increments, change how the time is displayed, and allow the user to denote the time zone associated with the time value.  Once I had the plugin configured the way I wanted, I simply had to write some code to validate the date and time string submitted from the form field, and I was done.  Very cool.

Simple Triangles with CSS

Recently, I had to create JavaScript-based replacements for 2 Java applets in an application I inherited.  One of the applets was a collapsible hierarchy tree of organizational units that used the conventional triangle icons (pointing right for closed, pointing down for open) to indicate state.

In past applications, I'd simply created actual triangle icons of the appropriate color for this sort of thing, but this time I decided I wanted to do it in pure CSS. 

After a quick search on the web (The Shapes of CSS is a nice resource on this topic) and a bit of trial-and-error, I came up with some CSS triangles that offset nicely from their tree items (and coded a blank triangle for items without children).  They work in all the common modern browsers and in IE as far back as IE 7:

.arrowNone {
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  border-top: 10px solid transparent;
  float:left;
  height: 0; 
  margin-right:5px;
  width: 0; 	
}

.arrowOpen {
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  border-top: 10px solid #666;
  float:left;
  height: 0; 
  margin-right:5px;
  margin-top:6px;
  width: 0; 
}

.arrowClosed {
  border-bottom: 5px solid transparent;
  border-left: 10px solid #666;
  border-top: 5px solid transparent;
  float:left;
  height: 0; 
  margin-right:5px;
  margin-top:4px;
  width: 0; 
}

Granted, they're not the smoothest of triangles, but they worked well enough for this purpose.