net.time4j.clock

Class NetTimeConnector<C extends NetTimeConfiguration>

java.lang.Object

net.time4j.clock.AbstractClock

net.time4j.clock.NetTimeConnector<C>

Type Parameters:

C - generic configuration type

All Implemented Interfaces:

TimeSource<Moment>

Direct Known Subclasses:

DaytimeClock, HttpClock, SntpConnector

public abstract class NetTimeConnector<C extends NetTimeConfiguration>
extends AbstractClock

Represents an abstract connection object to an internet time server.

A socket connection can be established by connect() and then the difference between the local computer clock and the net time can be queried. Next time queries of this clock are based on this difference and the local clock - until the next CONNECT.

Author:

Meno Hochschild

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	NetTimeConnector(C ntc) Creates a configured instance.

Method Summary

Methods

Modifier and Type	Method and Description
void	connect() Queries a time server for the current time.
Moment	currentTime() Yields the current time after a connection has been established at least once.
protected abstract Moment	doConnect() Will be called by connect().
protected abstract Class<C>	getConfigurationType() Yields the configuration type.
Moment	getLastConnectionTime() Yields the time of last connection.
long	getLastOffsetInMicros() Yields the last offset between net time and local time in microseconds.
C	getNetTimeConfiguration() Yields the current configuration parameters.
boolean	isLogEnabled() Determines if the internal logging is enabled.
boolean	isRunning() The clock is running as soon as there was established a connection at least once.
protected C	loadNetTimeConfiguration() Loads the configuration parameters via a ServiceLoader.
protected void	log(String prefix, String message) Logs given message if a PrintWriter has been installed.
boolean	reconfigure() Queries the configuration parameters to be used for the next connection.
void	setLogWriter(PrintWriter out) Installs a logging stream for any messages during connection.

Methods inherited from class net.time4j.clock.AbstractClock

inLocalView, inZonalView, inZonalView

Methods inherited from class java.lang.Object

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

Constructor Detail

NetTimeConnector

protected NetTimeConnector(C ntc)

Creates a configured instance.

Parameters:

ntc - Verbindungskonfiguration

Method Detail

currentTime

public Moment currentTime()

Yields the current time after a connection has been established at least once.

If there was no connection yet then this method just displays the time of clock construction. Note that this method is still sensible for any local clock change triggered by the underlying operating system. If an application needs a fresh internet time then following code can be used instead (causing network traffic):

  NetTimeConnector<?> clock = ...;
  clock.connect();
  Moment currentTime = clock.getLastConnectionTime();
 

Returns:

Moment

See Also:

isRunning()

isRunning

public boolean isRunning()

The clock is running as soon as there was established a connection at least once.

If there is not yet any connection then this clock will only display the time of its construction.

Returns:

boolean

See Also:

connect()

connect

public final void connect()
                   throws IOException

Queries a time server for the current time.

The result can then be achieved by the method currentTime() which is based on the network offset calculated in last connection. A connection to the server only happens in this method and not in the method currentTime().

Throws:

IOException - if connection fails or in case of any inconsistent server answers

See Also:

currentTime()

reconfigure

public final boolean reconfigure()

Queries the configuration parameters to be used for the next connection.

The configuration will be determined by a ServiceLoader. If not available then this connector will just choose the configuration which was given during construction of this instance. Any possible IllegalStateException will be logged to the error console. This method delegates to loadNetTimeConfiguration().

Returns:

true if successful else false

See Also:

loadNetTimeConfiguration()

getNetTimeConfiguration

public C getNetTimeConfiguration()

Yields the current configuration parameters.

Returns:

configuration object

See Also:

reconfigure()

setLogWriter

public void setLogWriter(PrintWriter out)

Installs a logging stream for any messages during connection.

Parameters:

out - output stream (null disables logging)

isLogEnabled

public boolean isLogEnabled()

Determines if the internal logging is enabled.

Returns:

true if there is any installed log writer else false

See Also:

setLogWriter(PrintWriter)

getLastConnectionTime

public Moment getLastConnectionTime()

Yields the time of last connection.

Returns:

moment of last connection or null if there was not any connection yet

See Also:

connect()

getLastOffsetInMicros

public long getLastOffsetInMicros()

Yields the last offset between net time and local time in microseconds.

Returns:

offset in microseconds (0 if there was not any connection yet)

See Also:

connect()

doConnect

protected abstract Moment doConnect()
                             throws IOException,
                                    ParseException

Will be called by connect().

Returns:

queried current time

Throws:

IOException - in case of any connection failure

ParseException - if the server reply is not readable

See Also:

connect()

loadNetTimeConfiguration

protected C loadNetTimeConfiguration()

Loads the configuration parameters via a ServiceLoader.

Subclasses should always start by calling super.loadNetTimeConfiguration() if this method is overridden.

Returns:

loaded configuration parameters

Throws:

IllegalStateException - in case of any configuration error

See Also:

reconfigure()

log

protected void log(String prefix,
       String message)

Logs given message if a PrintWriter has been installed.

Parameters:

prefix - optional prefix

message - message to be logged

See Also:

setLogWriter(PrintWriter)

getConfigurationType

protected abstract Class<C> getConfigurationType()

Yields the configuration type.

Returns:

configuration type