com.jrockit.memleak
Class Policy

java.lang.Object
  com.jrockit.memleak.Policy

Direct Known Subclasses:

Policy.TimeStampPolicy, Policy.TokenPolicy

public abstract class Policy
extends java.lang.Object

Policy to control caching, prefetch, and synchronous behavior of Memleak remote operations.

The policy mainly affects operations in two ways:

• For cheap operations, careful policy selection and operation order may be used to hide round trip delays.
• For expensive operations, the policy is mostly used to avoid recalculating results when sufficiently new results are already cached.

Author:

mpersson

Nested Class Summary

static class	Policy.TimeStampPolicy A Policy only accepting values arriving after this point in time.
static class	Policy.TokenPolicy Policy with a notification token.

Field Summary

static Policy	CACHED_OR_NULL Policy when you don't want any round trips, just the latest (if anything) already in the cache.
static Policy	NOTHING_CACHED Policy when you don't want anything that is cached.
static Policy	PREFETCH_SOMETHING Initiate prefetch if nothing is cached.
static Policy	SOMETHING Policy when you just want something (non-null), but don't care if it is old.

Constructor Summary

protected

Policy() Internal constructor for subclasses.

Method Summary

protected abstract Policy	createPrefetch() Create a new prefetching Policy.
Policy	derivedPrefetch()
static Policy.TokenPolicy	forToken(java.lang.Object token) Create a prefetch Policy.TokenPolicy that uses token to notify when the result has arrived.
static Policy.TimeStampPolicy	fromNow() Create a new Policy.TokenPolicy only accepting values arriving after this point in time.
<T> T	getAcceptable(IResult<T> result)
boolean	isDoneOrToken(IResult<?> result)
boolean	requireNewerThan(IResult<?> result)

Methods inherited from class java.lang.Object

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

Field Detail

CACHED_OR_NULL

public static final Policy CACHED_OR_NULL

Policy when you don't want any round trips, just the latest (if anything) already in the cache. (This may still cause round trips in non-caching implementations.)

SOMETHING

public static final Policy SOMETHING

Policy when you just want something (non-null), but don't care if it is old. Only does round trips when nothing is cached.

PREFETCH_SOMETHING

public static final Policy PREFETCH_SOMETHING

Initiate prefetch if nothing is cached.

NOTHING_CACHED

public static final Policy NOTHING_CACHED

Policy when you don't want anything that is cached. This will cause round trips.

Constructor Detail

Policy

protected Policy()

Internal constructor for subclasses.

Method Detail

fromNow

public static Policy.TimeStampPolicy fromNow()

Create a new Policy.TokenPolicy only accepting values arriving after this point in time. It is recommended that this is only used on explicit user request, such as a refresh.

Returns:

a Policy.TimeStampPolicy only accepting values from this point in time.

forToken

public static Policy.TokenPolicy forToken(java.lang.Object token)

Create a prefetch Policy.TokenPolicy that uses token to notify when the result has arrived.

Parameters:

token -

Returns:

a Policy.TokenPolicy

See Also:

INotificationService

createPrefetch

protected abstract Policy createPrefetch()

Create a new prefetching Policy.

Returns:

the policy

requireNewerThan

public boolean requireNewerThan(IResult<?> result)

Parameters:

result -

Returns:

true if a newer result than result is needed.

getAcceptable

public <T> T getAcceptable(IResult<T> result)
                throws GarbageCollectedException,
                       SpiException

Type Parameters:

T -

Parameters:

result -

Returns:

the value or possibly null if the result is pending and this policy is non-blocking.

Throws:

GarbageCollectedException

SpiException

isDoneOrToken

public boolean isDoneOrToken(IResult<?> result)

Parameters:

result -

Returns:

The result of result.isDone()

derivedPrefetch

public Policy derivedPrefetch()

Returns:

a policy similar to this one but that triggers a prefetch if needed. When used in an operation, the return value (typically null) should be ignored.