com.openharbor.beck.map
Class PollableURL

java.lang.Object
  com.openharbor.beck.map.PollableURL

All Implemented Interfaces:

PollableInput

public class PollableURL

extends java.lang.Object

implements PollableInput

A document identified by a URL, with a relatively efficient method to check whether it has changed. This class is not thread-safe.

Nested Class Summary

protected static class

PollableURL.Description Properties of a document that are examined to decide whether it has changed.

Field Summary

protected long	expirationTime
protected org.apache.commons.logging.Log	log
protected static long	NEVER
protected static long	UNKNOWN
protected static long	UNKNOWN_TIME

Fields inherited from interface com.openharbor.beck.map.PollableInput

SECONDS

Constructor Summary

PollableURL(java.net.URL url)

Method Summary

protected PollableURL.Description	getDescription(java.net.URLConnection connection) This method must not consume data from getInputStream(connection).
protected void	getExpirationTime(java.net.URLConnection connection) Note the document's expiration time (if any).
protected java.io.InputStream	getInputStream(java.net.URLConnection connection)
java.lang.String	getSystemID() The SystemID that identifies the input source, or null if its SystemID is unknown.
java.net.URL	getURL()
java.io.InputStream	input() Begin reading the data (as a stream of bytes).
java.io.InputStream	inputIfModified() Begin reading the data (as a stream of bytes) if it has changed since the last call to input() or inputIfModified().
void	pollSoon() Check for a change in the data next time inputIfModified is called, regardless of the currently acceptable staleness.
void	setAcceptableStaleness(long msec) Set the maximum amount of time that may elapse from a change in the data until the change is detected by this object.

Methods inherited from class java.lang.Object

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

Field Detail

log

protected final org.apache.commons.logging.Log log

expirationTime

protected long expirationTime

UNKNOWN

protected static final long UNKNOWN

See Also:

Constant Field Values

UNKNOWN_TIME

protected static final long UNKNOWN_TIME

See Also:

Constant Field Values

NEVER

protected static final long NEVER

See Also:

Constant Field Values

Constructor Detail

PollableURL

public PollableURL(java.net.URL url)

Method Detail

getURL

public java.net.URL getURL()

setAcceptableStaleness

public void setAcceptableStaleness(long msec)

Description copied from interface: PollableInput

Set the maximum amount of time that may elapse from a change in the data until the change is detected by this object.

Specified by:

setAcceptableStaleness in interface PollableInput

Parameters:

msec - the acceptable staleness, in units of milliseconds.

getSystemID

public java.lang.String getSystemID()

Description copied from interface: PollableInput

The SystemID that identifies the input source, or null if its SystemID is unknown.

Specified by:

getSystemID in interface PollableInput

input

public java.io.InputStream input()
                          throws java.io.IOException

Description copied from interface: PollableInput

Begin reading the data (as a stream of bytes).

Specified by:

input in interface PollableInput

Throws:

java.io.IOException

inputIfModified

public java.io.InputStream inputIfModified()
                                    throws java.io.IOException

Description copied from interface: PollableInput

Begin reading the data (as a stream of bytes) if it has changed since the last call to input() or inputIfModified().

Specified by:

inputIfModified in interface PollableInput

Returns:

a stream that will produce the data, or null to indicate that the data have not changed.

Throws:

java.io.IOException

pollSoon

public void pollSoon()

Description copied from interface: PollableInput

Check for a change in the data next time inputIfModified is called, regardless of the currently acceptable staleness.

Specified by:

pollSoon in interface PollableInput

getDescription

protected PollableURL.Description getDescription(java.net.URLConnection connection)
                                          throws java.io.IOException

This method must not consume data from getInputStream(connection). If it must consume connection.getInputStream(), then this.getInputStream must be overridden to compensate; e.g. using a 'read-ahead' buffer.

Throws:

java.io.IOException

getExpirationTime

protected void getExpirationTime(java.net.URLConnection connection)

Note the document's expiration time (if any).

getInputStream

protected java.io.InputStream getInputStream(java.net.URLConnection connection)
                                      throws java.io.IOException

Throws:

java.io.IOException