• For a concise description of the goals and directions of iCal4j please take a look at docs/index.html.

• You will find examples of how to use iCal4j at docs/introduction.html and throughout the API documentation.

• Detailed descriptions of changes included in each release may be found in the CHANGELOG.

• iCal4j was created with the help of eclipse version 3.2 [https://eclipse.org]. Note that the project metadata included in the source version of iCal4j may not be compatible with prior versions of eclipse.

• Java 5 or later

• commons-codec

• commons-lang3

• slf4j/jcl-over-slf4j

• junit (for unit testing only)

iCal4j includes the Gradle wrapper for a simpler and more consistent build.

Run unit tests

./gradlew clean test

Build a new release

./gradlew clean test release -PreleaseVersion=2.0.0

Upload release binaries and packages

RELEASE_VERSION=2.0.0 ./gradlew uploadArchives uploadDist

After installing Maven2 and adding to your path, you need to modify your local profiles https://wiki.modularity.net.au/ical4j/index.php?title=Maven2. Then open a command prompt to the location of the iCal4j source and execute the following:

[iCal4j-2.0-beta1-src] >mvn clean install or [iCal4j-2.0-beta1-src] >mvn clean install -P modularity-snapshots

This will build and install iCal4j in your local repository. Build artifacts are generated in the 'target' directory.

If you have downloaded the source distribution, you should be able to package a JAR file simply by running ant in the root directory. e.g:

C:\Libs\iCal4j-2.0-beta1-src>ant

If for some reason you would like to override the default build classpath, I would suggest creating a "build.properties" file (see the provided sample) in the root directory and add overridden properties to this. You can also override properties via Java system properties (e.g. -Dproject.classpath="..."). You shouldn't need to modify the "build.xml" at all, so if you do find a need let me know and I'll try to rectify this.

iCal4j now has the capability to "relax" its parsing rules to enable parsing of *.ics files that don't properly conform to the iCalendar specification (RFC2445)

• You can relax iCal4j's unfolding rules by specifying the following system property:

  ical4j.unfolding.relaxed=true

Note that I believe this problem is not restricted to Mozilla calendaring products, but rather may be caused by UNIX/Linux-based applications relying on the default newline character (LF) to fold long lines (KOrganizer also seems to have this problem). This is, however, still incorrect as by definition long lines are folded using a (CRLF) combination.

I've obtained a couple of samples of non-standard iCalendar files that I've included in the latest release (0.9.11). There is a Sunbird, phpicalendar, and a KOrganizer sample there (open them in Notepad on Windows to see what I mean).

It seems that phpicalendar and KOrganizer always use LF instead of CRLF, and in addition KOrganizer seems to fold all property parameters and values (similar to Mozilla Calendar/Sunbird).

Mozilla Calendar/Sunbird uses CRLF to fold all property parameter/values, however it uses just LF to fold long lines (i.e. longer than 75 characters).

The latest release of iCal4j includes changes to UnfoldingReader that should work correctly with Mozilla Calendar/Sunbird, as long as the ical4j.unfolding.relaxed system property is set to true.

KOrganizer/phpicalendar files should also work with the relaxed property, although because ALL lines are separated with just LF it also relies on the StreamTokenizer to correctly identify LF as a newline on Windows, and CRLF as a newline on UNIX/Linux. The API documentation for Java 1.5 says that it does do this, so if you still see problems with parsing it could be a bug in the Java implementation.

• You may also relax the parsing rules of iCal4j by setting the following system property:

  ical4j.parsing.relaxed=true

This property is intended as a general relaxation of parsing rules to allow for parsing otherwise invalid calendar files. Initially enabling this property will allow for the creation of properties and components with illegal names (e.g. Mozilla Calendar's "X" property). Note that although this will allow for parsing calendars with illegal names, validation will still identify such names as an error in the calendar model.

• Microsoft Outlook also appears to provide quoted TZID parameter values, as follows:

  DTSTART;TZID="Pacific Time (US & Canada),Tijuana":20041011T223000

To allow for compatibility with such iCalendar files you should specify the following system property:

ical4j.compatibility.outlook=true

The full set of system properties may be found in net.fortuna.ical4j.util.CompatibilityHints.

Supporting timezones in an iCalendar implementation can be a complicated process, mostly due to the fact that there is not a definitive list of timezone definitions used by all iCalendar implementations. This means that an iCalendar file may be produced by one implementation and, if the file does not include all definitions for timezones relevant to the calendar properties, an alternate implementation may not know how to interpret the timezone identified in the calendar (or worse, it may interpret the timezone differently to the original implementation). All of these possibilities mean unpredictable behaviour which, to put it nicely, is not desireable.

iCal4j approaches the problem of timezones in two ways: The first and by far the preferred approach is for iCalendar files to include definitions for all timezones referenced in the calendar object. To support this, when an existing calendar is parsed a list of VTimeZone definitions contained in the calendar is constructed. This list may then be queried whenever a VTimeZone definition is required.

The second approach is to rely on a registry of VTimeZone definitions. iCal4j includes a default registry of timezone definitions (derived from the Olson timezone database - a defacto standard for timezone definitions), or you may also provide your own registry implementation from which to retreieve timezones. This approach is required when constructing new iCalendar files.

Note that the intention of the iCal4j model is not to provide continuous validation feedback for every change in the model. For this reason you are free to change timezones on Time objects, remove or add TzId parameters, remove or add VTimeZone definitions, etc. without restriction. However when validation is run (automatically on output of the calendar) you will be notified if the changes are invalid.

Choosing Java 1.4 as the minimum required JVM was initially slightly arbitrary, and probably based on the fact that most people were using 1.4 as a minimum.

Since then, however, there are two features of 1.4 I can think of that iCal4j requires: - the URI class; - and the java.util.regex.* package (used in StringUtils).

If you don't think you will be needing these features in your own code, you may want to try compiling iCal4j with JDK 1.4 using the "-target 1.3" option but without specifying an alternative "-bootclasspath" option. From what I can tell, this should generate 1.3 bytecode that you can run on a 1.3 JVM. Note however, that if your code does cause iCal4j to load the URI or java.util.regex.* references then it will fail on a 1.3 JVM (as these APIs aren't available).

If you intend to use and distribute iCal4j in your own project please follow these very simple guidelines:

• Make a copy of the LICENSE, rename it to LICENSE.ical4j, and save it to the directory where you are re-distributing the iCal4j JAR.

• I don't recommend extracting the iCal4j classes from its JAR and package in another JAR along with other classes. It may lead to version incompatibilites in the future. Rather I would suggest to include the ical4j.jar in your classpath as required.