Fatal Error in the logs by Grails

I recently started working on a project using Grails and the following message in the logs appeared consistently and annoyed me quite a lot.

[Fatal Error] :-1:-1: Premature end of file.

So I started digging through the code and searching the web for an answer. And I found it. It is a bug that has been reported to Grails and you can find it at GRAILS-3088. It apparently affects Grails 1.0.3 (which I am using) and it should be fixed in next release, 1.0.4.

The bug is triggered with each request from Firefox 3 and Opera 9.5 and even Firefox 2 if you render the response as "text/xml" using

withFormat { xml { render(contentType:"text/xml"){ ... } } }

The current workaround suggested by Graeme Rocher is to edit Config.groovy file and remove (or comment out) "text/xml" from the Grails MIME types mapping

grails.mime.types = [ html: ['text/html','application/xhtml+xml'],
//                      xml: ['text/xml', 'application/xml'],
                      text: 'text-plain',

This works for me. No more annoying messages in the logs. I am not quite sure how or if it affects XML responses. But I do not need those for now, so I will worry about that later, if I need to

HTML id attribute valid values

Many (if not all) HTML tags can have id attribute. This attribute uniquely identifies the tag on a single HTML page. Web designers use ids when they design the page using CSS. Web developers use ids for retrieving DOM objects via JavaScript or functional testing of their sites.

Despite the wide use of id attribute, many of us get it wrong, the value of the id tag attribute to be precise.

According to the HTML 4.0 specification for basic types:

ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").

This is a very basic rule and yet many of us get it wrong, not on purpose of course.

The most common mistake come with web applications that display data from a database. Most commonly a database record is uniquely identified in the database by a record id. This is number that is unique per database table. The common mistake is to use this (database) id as a value of the id attribute on a HTML page. The problem is that the database id is a number, but HTML ids cannot start with a digit. Remember HTML ids must start with a letter A-Z or a-z. Therefore the database id needs to be pre-pended with at least a single letter.

Even worse, I have seen web applications to use entity names as ids. These names are semi-unique, but may contain international characters, characters outside of A-Z and a-z range and even spaces.

If you are going to use a prefix before the database id and you want to separate the two, I strongly advise you to use underscore ("_"). My reasons are the following:

Don't use spaces (" ")! The reason for this is simple. Space character is not a valid for id or name attribute.

Don't use hyphens ("-")! If you intend to use an id with JavaScript in the form document.idname.value, you must use a name that is a valid JavaScript variable name. Hyphen (or minus) would break the JavaScript on your page.

Don't use colons (":") or periods (".")! These characters are valid, however if you decide to use CSS or some JavaScript library that uses CSS-like selectors (e.g. jQuery), periods will be mistaken for CSS class selectors and colons for pseudo-class selectors (e.g. :hover for links).

For the geeky ones, it is possible to start an id with a number (if you really want to) but you need to represent this number with its Unicode escaped character.

Process terminated with exit code 3

This is a reminder to myself.

I had a trouble with IntelliJ IDEA today. It was the same as I had some time ago on a different computer.

Process terminated with exit code 3

After a bit of digging around the solution was obvious: increase the maximum heap size in Settings | Compiler.

How to get the server's timezone

The problem

How to get the server's timezone display name correctly and display it to the user in his locale.

server's default timezone

Firstly, you need to get the server's default timezone. This is easily achieved by the following call

final TimeZone timeZone = TimeZone.getDefault();

use daylight time?

Secondly, you need to find out if this timezone uses daylight time. This is important as some timezones change their names during daylight saving. Don't use the TimeZone.useDaylightTime() method

//final boolean daylight = timeZone.useDaylightTime();

This method works fine only for systems where the timezone never changes. If the administrator changes the time on the server, this change won't be reflected in subsequent calls. What you need to do instead, is to find out is the daylight savings is on right now.

final boolean daylight = timeZone.inDaylightTime(new Date());

user's locale

The last important step is to get the right locale, the locale you want this timezone name to display in. You could call Locale.getDefault(), but this returns server's default locale. You want the locale that the user is using. In a web application, the user's locale can be obtained from getLocale() method of ServletRequest object.

final Locale locale = servletRequest.getLocale();

final step - timezone display name

Now we can call getDisplayName method with all required parameters.

return timeZone.getDisplayName(daylight, TimeZone.LONG, locale);

Solution

To put this all together, the final solution may look like this method

private String getServerTimeZoneDisplayName()
{
    final TimeZone timeZone = TimeZone.getDefault();
    final boolean daylight = timeZone.inDaylightTime(new Date());
    final Locale locale = servletRequest.getLocale();
    return timeZone.getDisplayName(daylight, TimeZone.LONG, locale);
}

References

• Java TimeZone class
• JEE ServletRequest class
• JRA-15488 - Shows incorrect time (zone) when subscribing to filter