Time Zone

Overview

The time zone used to process requests and events is, by default, determined by the JVM's default (by use of the getDefault method of java.util.TimeZone).

In this section, we will discuss how to configure ZK to use a time zone other than JVM's default. For example, you might configure ZK to use the preferred time zone that a user specified in his or her profile.

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The Decision Sequence of Time Zone

The time zone is decided in the following sequence.

1. It checks if an attribute called org.zkoss.web.preferred.timeZone defined in the HTTP session (aka., Session). If so, use it.
2. It checks if an attribute called org.zkoss.web.preferred.timeZone defined in the Servlet context (aka., Application). If so, use it.
3. It checks if a property called org.zkoss.web.preferred.timeZone defined in the library property (i.e., Library). If so, use it.
4. If none of them is found, JVM's default will be used.

With this sequence in mind, you could configure ZK to use the correct time zone based on the application requirements.

Application-level Time Zone

If you want to use the same time zone for all users of the same application, you can specify the time zone in the library property. For example, you could specify the following in WEB-INF/zk.xml:

<library-property>
    <name>org.zkoss.web.preferred.timeZone</name>
    <value>GMT-8</value>
</library-property>

where the value can be anything accepted by the getTimeZone method of java.util.TimeZone

Alternatively, if you prefer to specify it in Java, you could invoke Library.setProperty(String, String). Furthermore, to avoid typo, you could use Attributes.PREFERRED_TIME_ZONE as follows.

Library.setProperty(Attributes.PREFERRED_TIME_ZONE, "PST");

Per-user Time Zone

Because ZK will check if a session attribute for the default time zone, you could configure ZK to have per-user time zone by specifying the attribute in a session.

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

 void login(String username, String password) {
     //check password
     ...
     TimeZone preferredTimeZone = ...; //decide the time zone (from, say, database)
     session.setAttribute(Attributes.PREFERRED_TIME_ZONE, preferredTimeZone);
     ...
 }

The Request Interceptor

Like configuring locale, you can prepare the time zone for the given session by the use of the request interceptor. Please refer to the Locale section for more information.

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