53673d6c59
java.util.concurrent's ScheduledExecutorService and its #schedule* methods allow for an 'initialDelay' parameter in milliseconds. Similarly, Spring's TaskExecutor abstraction allows for a concrete 'startTime' expressed as a Date. However, Spring's <task:scheduled> XML element and @Scheduled annotation have, to date, not allowed for an initial delay parameter that can be propagated down to the underlying TaskScheduler/ScheduledExecutorService. This commit introduces initial-delay and #initialDelay attributes to task:scheduled and @Scheduled respectively, both indicating the number of milliseconds to wait before the first invocation of the method in question. Specifying a delay in this fashion is only valid in conjunction with fixed-rate and fixed-delay tasks (i.e. not with cron or trigger tasks). The principal changes required to support these new attributes lie in ScheduledTaskRegistrar, which previously supported registration of tasks in the form of a Runnable and a Long parameter indicating (in the case of fixed-rate and fixed-delay tasks), the interval with which the task should be executed. In order to accommodate a third (and optional) 'initialDelay' parameter, the IntervalTask class has been added as a holder for the Runnable to be executed, the interval in which to run it, and the optional initial delay. For symmetry, a TriggerTask and CronTask have also been added, the latter subclassing the former. And a 'Task' class has been added as a common ancestor for all the above. One oddity of the implementation is in the naming of the new setters in ScheduledTaskRegistrar. Prior to this commit, the setters were named #setFixedDelayTasks, #setFixedRateTasks, etc, each accepting a Map<Runnable, long>. In adding new setters for each task type, each accepting a List<IntervalTask>, List<CronTask> etc, naturally the approach would be to use method overloading and to introduce methods of the same name but with differing parameter types. Unfortunately however, Spring does not support injection against overloaded methods (due to fundamental limitations of the underlying JDK Introspector). This is not a problem when working with the ScheduledTaskRegistrar directly, e.g. from within a @Configuration class that implements SchedulingConfigurer, but is a problem from the point of view of the ScheduledTasksBeanDefinitionParser which parses the <task:scheduled> element - here the ScheduledTaskRegistrar is treated as a Spring bean and is thus subject to these limitations. The solution to this problem was simply to avoid overloading altogether, thus the naming of the new methods ending in "List", e.g. #setFixedDelayTasksList, etc. These methods exist primarily for use by the BeanDefinitionParser and are not really intended for use by application developers. The Javadoc for each of the new methods makes note of this. Issue: SPR-7022
Spring Framework
The Spring Framework provides a comprehensive programming and configuration model for modern Java-based enterprise applications - on any kind of deployment platform. A key element of Spring is infrastructural support at the application level: Spring focuses on the "plumbing" of enterprise applications so that teams can focus on application-level business logic, without unnecessary ties to specific deployment environments.
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