/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.isis.applib.clock;
import java.sql.Timestamp;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
import org.joda.time.LocalDate;
import org.joda.time.LocalDateTime;
import org.apache.isis.applib.FatalException;
import org.apache.isis.applib.RecoverableException;
import org.apache.isis.applib.Defaults;
import org.apache.isis.applib.fixtures.FixtureClock;
/**
* Provides a mechanism to get (and possible to set) the current time.
*
* <p>
* The clock is used primarily by the temporal value classes, and is accessed by
* the NOF as a singleton. The actual implementation used can be configured at
* startup, but once specified the clock instance cannot be changed.
*
* <p>
* Unless another {@link Clock} implementation has been installed, the first
* call to {@link #getInstance()} will instantiate an implementation that just
* uses the system's own clock. Alternate implementations can be created via
* suitable subclasses, but this must be done <b><i>before</i></b> the first
* call to {@link #getInstance()}. See for example
* {@link FixtureClock#getInstance()}.
*/
public abstract class Clock {
private static Clock instance;
private static boolean isReplaceable = true;
/**
* Returns the (singleton) instance of {@link Clock}.
*
* <p>
* Unless it has been otherwise created, will lazily instantiate an
* implementation that just delegate to the computer's own system clock (as
* per {@link System#currentTimeMillis()}.
*
* @return
*/
public final static Clock getInstance() {
if (!isInitialized()) {
instance = new SystemClock();
isReplaceable = false;
}
return instance;
}
/**
* Whether has been initialized or not.
*/
public static boolean isInitialized() {
return instance != null;
}
/**
* The time as the number of millseconds since the epoch.
*
* @see Date#getTime()
*/
public static long getTime() {
return getInstance().time();
}
/**
* Convenience method returning the current {@link #getTime() time}
* according to this Clock as a mutable {@link Calendar}. Consider replacing
* with {@link #getTimeAsDateTime()
*/
@Deprecated
public static Calendar getTimeAsCalendar() {
return getInstance().timeAsCalendar();
}
/**
* Convenience method returning the current {@link #getTime() time}
* according to this Clock as a (nominally im)mutable {@link Date}. You
* should now use {@link #getTimeAsDateTime()}
*
*/
@Deprecated
public static Date getTimeAsDate() {
return new Date(getTime());
}
public static LocalDate getTimeAsLocalDate() {
final DateTimeZone timeZone = DateTimeZone.forTimeZone(TimeZone.getDefault());
return new LocalDate(getTime(), timeZone);
}
public static LocalDateTime getTimeAsLocalDateTime() {
return new LocalDateTime(getTime(), Defaults.getTimeZone());
}
/**
* Returns the {@link #getTime() time} as a Joda {@link DateTime},
* using the {@link Defaults#getTimeZone() timezone} as
* {@link Defaults#setTimeZone(org.joda.time.DateTimeZone) currently set}.
*/
public static DateTime getTimeAsDateTime() {
return new DateTime(getTime(), Defaults.getTimeZone());
}
private static void ensureReplaceable() {
if (!isReplaceable && instance != null) {
throw new RecoverableException("Clock already set up");
}
}
public static Timestamp getTimeAsJavaSqlTimestamp() {
return new java.sql.Timestamp(getTimeAsDateTime().getMillis());
}
/**
* Allows subclasses to remove their implementation.
*
* @return whether a clock was removed.
*/
protected static boolean remove() {
ensureReplaceable();
if (instance == null) {
return false;
}
instance = null;
return true;
}
protected Clock() {
ensureReplaceable();
instance = this;
}
public final Calendar timeAsCalendar() {
final Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(Clock.getTime());
return cal;
}
/**
* The current time since midnight, January 1, 1970 UTC.
*
* <p>
* Measured in milliseconds, modeled after (and possibly implemented by)
* {@link System#currentTimeMillis()}.
*/
protected abstract long time();
}
final class SystemClock extends Clock {
@Override
protected long time() {
return System.currentTimeMillis();
}
}