Date and Time Formatting

Overview

By default, the format of date and time, especially the format of Datebox and Timebox, is determined by the JVM's default and the current locale.

In this section, we will discuss how to configure ZK to use the format other than the JVM. For example, you could configure ZK to use the preferred format based on the user's preferences.

The Decision Sequence of Format

The format of date and time is decided in the following sequence.

1. It checks if an attribute called org.zkoss.web.preferred.dateFormatInfo defined in the HTTP session (i.e., Session). If so, it will be used by assuming the value is an instance or a class of DateFormatInfo.
2. It checks if an attribute called org.zkoss.web.preferred.dateFormatInfo defined in the servlet context (i.e., Application). If so, it will be used by assuming the value is an instance or a class of DateFormatInfo.
3. It checks if a property called org.zkoss.web.preferred.dateFormatInfo defined in the library property (i.e., Library). If so, it will be used by assuming the value is a class of DateFormatInfo.
4. If none of them is found, it uses the JVM's default based on the current locale

In other words, to configure ZK to use the format other than the JVM's default, you have to:

1. Implements DateFormatInfo to provide the format you want
2. Specify the class or an instance of it in the session's attribute or application's attribute depending on the requirement of your application.

If a class or the class's name is specified, an instance of it is instantiated each time the server receives a request from the client. It means the implementation needs not to be thread safe, but at the cost of instantiation. On the other hand, if an instance is specified as the attribute value, it will be used for all requests, so it has to be thread safe.

Also notice that you could specify short, long and other standard styling in the format property of datebox and timebox, such that the corresponding format of the styling will be used instead of the default, meidum. For more information, please refer to the Per-component Format section.

Application-level Format

If you want to use the same format for all users, you could specify your implementation of DateFormatInfo in the library property. For example,

<library-property>
    <name>org.zkoss.web.preferred.dateFormatInfo</name>
    <value>foo.MyDateFormatInfo</value>
</library-property>

where we assume the implementation is named foo.MyDateFormatInfo.

Per-user Format

If you'd like to configure ZK to allow each user (aka., session) has an independent format, you could store an instance of your implementation of DateFormatInfo in the session's attribute.

For example, you could do this when a user logins.

import org.zkoss.web.Attributes;
...

 void login(String username, String password) {
     //check password
     ...
     session.setAttribute(Attributes.PREFERRED_DATE_FORMAT_INFO,
         new foo.MyDateFormatInfo(session));
     ...
 }

where we assume the implementation is named foo.MyDateFormatInfo.

Per-component Format

Datebox and Timebox allow a developer to specify any format he prefer for any instance. For example,

<datebox format="MM d, yyyy"/>
<timebox format="HH:mm"/>

However, it is usually better to design a page that depends on the configuration as described above, rather than specify the format explicitly in each page. It can be done by specifying the styling rather than the real format in the format property (Datebox.setFormat(String) and Timebox.setFormat(String)). There are totally four different styling: short, medium, long and full (representing the styling defined in java.text.DateFormat, SHORT, MEDIUM, LONG and FULL). For example,

<datebox format="short"/>
<datebox format="long"/>
<timebox format="medium"/>

Then, the real format will be decided by your implementation of DateFormatInfo, if any, or the JVM's default.

In additions, you could specify the date/time format in the syntax of styling_for_date+styling_for_time, such as:

<datebox format="long+medium"/>

which specifies the date/time format with the long styling for date and the medium styling for time.

Per-component Locale

In additions to the current locale, you could specify the locale for individual instances of datebox and timebox. Then, the real format will depend on the locale and the format you specified. For example,

<datebox format="medium" locale="de"/>
<timebox format="long" locale="fr"/>

Note: the language of the format and the datebox's calendar is the same as the locale you specified. [Since 5.0.8]

Version History

Version	Date	Content
5.0.7	April 2011	The per-session format of datebox/timebox was introduced. Prior to 5.0.7, the format depends only on locale.