de.frame4j.util

Class AppHelper

java.lang.Object

de.frame4j.util.AppHelper

@MinDoc(copyright="Copyright  1999 - 2009, 2021 A. Weinert",
        author="Albrecht Weinert",
        version="V.50",
        lastModified="4.06.2021",
        usage="use the basic services",
        purpose="provide helper methods for applications")
public abstract class AppHelper
extends Object

Helper for applications.

This abstract class contains some (static) helpers for applications.

Copyright © 1999 - 2009 2021 Albrecht Weinert

   weinert-automation.de        a-weinert.de

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      \/  \/   \__/        \__/|_

See Also:

TextHelper, Verbos

Field Summary

Fields

Modifier and Type	Field and Description
static Class<?>[]	ECL Empty Class array.
static Object[]	EOB Empty Object array.

Method Summary

Modifier and Type	Method and Description
static String	getActTime() The actual (system) time as text.
static InputStream	getAsRessourceStream(CharSequence fileName) Designate an input stream from a file or a resource.
static Timer	getTimer() Fetch one (singleton) Timer.
static long	scheduleAbsolute(TimerTask task, long start, long period) Schedule a task for absolute start and repeated execution.
static void	scheduleAtFixedRate(TimerTask task, long delay, long period) Schedule a task for relative (delayed) start and repeated execution.
static void	setProxy(boolean on, String proxyHost, String proxyPort) Set the system properties governing the use of a (LAN) proxy.
static boolean	sleep(long millis) Delay programme execution by just waiting.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ECL

public static final Class<?>[] ECL

Empty Class array.

EOB

public static final Object[] EOB

Empty Object array.

Method Detail

sleep

public static final boolean sleep(long millis)

Delay programme execution by just waiting.

The effect is that of the (used) method Thread.sleep(long).

As distinguished from Thread's method this sleep() throws no Exception. An early return due to an interrupt of the wait/sleep is signalled by returning false.

The time to wait is specified as milliseconds, the accuracy being runtime dependent.

Parameters:

millis - (>0 !) wait time in ms

Returns:

true after uninterrupted expiration of the time

See Also:

ComVar.ONE_MINUTE, ComVar.ONE_HOUR, ComVar.ONE_DAY

setProxy

public static void setProxy(boolean on,
                            String proxyHost,
                            String proxyPort)

Set the system properties governing the use of a (LAN) proxy.

This method sets the (JVM) system variables for proxy behaviour.

Parameters:

on - false: use no proxy; both other parameters are taken in, even if so of no relevance.

proxyHost - Name of the proxy server of this (LAN) network segment (often proyx or cache); null or empty means no change.

proxyPort - Port of the proxy server of this (LAN) network segment; (often 8080); null or empty means no change.

getActTime

public static String getActTime()

The actual (system) time as text.

The actual platform time (supplied in the framework as common Time stamp is updated to system clock and then formatted according to AppLangMap.valueUL("wedaclock").

In the case of user language German the format is "D, d.m.Y, H:i:s"; in the case of English it would be "w, M d Y, H:i:s". That would give "Do, 05.02.2009, 13:45:19" or "Th, Feb. 05 2009, 13:45:19" respectively.

getAsRessourceStream

public static InputStream getAsRessourceStream(CharSequence fileName)
                                        throws SecurityException

Designate an input stream from a file or a resource.

Using the given fileName it is tried to produce and return an input stream connected or related to the class loader registered at start in ComVar.FRW_CLLD. Normally this would be a file contained in the (Frame4J's) deployment .jar-file.

null is returned if no original class loader (FRW_CLLD) is known or if no resource named fileName could be determined or found.

Returns:

an input stream in case of success

Throws:

SecurityException - if the trials to determine the resource were denied due to security reasons.

getTimer

public static Timer getTimer()

Fetch one (singleton) Timer.

One single Timer is able to handle thousands of TimerTasks also for multiple Threads.

So there has to be just one (singleton). This methods fetches it (as daemon).

Hint: Timer.cancel() shall never be called for this singleton Timer. It would destroy it for other users.

scheduleAtFixedRate

public static void scheduleAtFixedRate(TimerTask task,
                                       long delay,
                                       long period)
                                throws IllegalStateException,
                                       IllegalArgumentException

Schedule a task for relative (delayed) start and repeated execution.

After a delay the task will be started and periodically repeated afterwards. Variations in the scheduling period will be corrected in the next steps, so that in the long run there is a stable and precise frequency. In the example "tomorrow at 03:15:31, and then daily" would keep on about 3 hours 15 minutes and 31 seconds every day (except perhaps for leap seconds?).

Hint: day light saving switches keep the 24h period, but shift the tasks starting time of day by one hour. This might give surprising effects for daily administrative tasks.

See also Timer.scheduleAtFixedRate(java.util.TimerTask, long, long).

Parameters:

task - the task to be scheduled

delay - very first start delay in ms (>= 0 !)

period - repeating period in ms (> 0 !)

Throws:

IllegalArgumentException - if parameter values point to the past

IllegalStateException - if the task task was scheduled already or if it or the timer was stopped

See Also:

getTimer()

scheduleAbsolute

public static long scheduleAbsolute(TimerTask task,
                                    long start,
                                    long period)
                             throws IllegalStateException,
                                    IllegalArgumentException,
                                    NullPointerException

Schedule a task for absolute start and repeated execution.

This method is mostly equivalent to scheduleAtFixedRate(TimerTask, long, long). The difference is start being an absolute starting time as ms.

If start is in the past respectively less than about 1.5 s in the future multiples of period will be added to bring start between 1.5 s and 1.5 s + period to the future. This ensures meaningful starting conditions for the class Timer). The used start time is the return value.

Parameters:

task - the task planned to run

start - the time for first start (>= year 2009 !)

period - repeat rate in ms (milliseconds, > 10 !)

Returns:

start may be + n * period

Throws:

IllegalArgumentException - falls die Parameter point (to far) into past

IllegalStateException - if the task was planned already or if it or the Timer has ended already

NullPointerException - if task is null

See Also:

getTimer()