V
- the type of the value of this step@Beta @DoNotMock(value="Use ClosingFuture.from(Futures.immediate*Future)") public final class ClosingFuture<V> extends Object
A pipeline of ClosingFuture
s is a tree of steps. Each step represents either an
asynchronously-computed intermediate value, or else an exception that indicates the failure or
cancellation of the operation so far. The only way to extract the value or exception from a step
is by declaring that step to be the last step of the pipeline. Nevertheless, we refer to the
"value" of a successful step or the "result" (value or exception) of any step.
ListenableFuture
.
ClosingFuture
pipeline from a
callable block that may capture objects for later closing. To start a pipeline from a ListenableFuture
that doesn't create resources that should be closed later, you can use from(ListenableFuture)
instead.
ClosingFuture
step can be derived from one or more input ClosingFuture
steps in
ways similar to FluentFuture
s:
A step can be the input to at most one derived step. Once you transform its value, catch its exception, or combine it with others, you cannot do anything else with it, including declare it to be the last step of the pipeline.
transform(ClosingFunction, Executor)
or transformAsync(AsyncClosingFunction,
Executor)
on the input step.
catching(Class, ClosingFunction,
Executor)
or catchingAsync(Class, AsyncClosingFunction, Executor)
on the input step.
ClosingFuture
from two or more input steps, pass the input steps to whenAllComplete(Iterable)
or whenAllSucceed(Iterable)
or its overloads.
Future
. In addition, a
successfully cancelled step will immediately start closing all objects captured for later closing
by it and by its input steps.
ClosingFuture
pipeline must be ended. To end a pipeline, decide whether you want to
close the captured objects automatically or manually.
Future
that represents the result of the last step in the pipeline by
calling finishToFuture()
. All objects the pipeline has captured for closing will begin
to be closed asynchronously after the returned Future
is done: the future
completes before closing starts, rather than once it has finished.
FluentFuture<UserName> userName =
ClosingFuture.submit(
closer -> closer.eventuallyClose(database.newTransaction(), closingExecutor),
executor)
.transformAsync((closer, transaction) -> transaction.queryClosingFuture("..."), executor)
.transform((closer, result) -> result.get("userName"), directExecutor())
.catching(DBException.class, e -> "no user", directExecutor())
.finishToFuture();
In this example, when the userName
Future
is done, the transaction and the query
result cursor will both be closed, even if the operation is cancelled or fails.
finishToValueAndCloser(ValueAndCloserConsumer, Executor)
to get an object that holds the
final result. You then call ClosingFuture.ValueAndCloser.closeAsync()
to close the captured objects.
ClosingFuture.submit(
closer -> closer.eventuallyClose(database.newTransaction(), closingExecutor),
executor)
.transformAsync((closer, transaction) -> transaction.queryClosingFuture("..."), executor)
.transform((closer, result) -> result.get("userName"), directExecutor())
.catching(DBException.class, e -> "no user", directExecutor())
.finishToValueAndCloser(
valueAndCloser -> this.userNameValueAndCloser = valueAndCloser, executor);
// later
try { // get() will throw if the operation failed or was cancelled.
UserName userName = userNameValueAndCloser.get();
// do something with userName
} finally {
userNameValueAndCloser.closeAsync();
}
In this example, when userNameValueAndCloser.closeAsync()
is called, the transaction and
the query result cursor will both be closed, even if the operation is cancelled or fails.
Note that if you don't call closeAsync()
, the captured objects will not be closed. The
automatic-closing approach described above is safer.
Modifier and Type | Class and Description |
---|---|
static interface |
ClosingFuture.AsyncClosingCallable<V>
An operation that computes a
ClosingFuture of a result. |
static interface |
ClosingFuture.AsyncClosingFunction<T,U>
A function from an input to a
ClosingFuture of a result. |
static interface |
ClosingFuture.ClosingCallable<V>
An operation that computes a result.
|
static interface |
ClosingFuture.ClosingFunction<T,U>
A function from an input to a result.
|
static class |
ClosingFuture.Combiner
A builder of a
ClosingFuture step that is derived from more than one input step. |
static class |
ClosingFuture.Combiner2<V1,V2>
A generic
ClosingFuture.Combiner that lets you use a lambda or method reference to combine two ClosingFuture s. |
static class |
ClosingFuture.Combiner3<V1,V2,V3>
A generic
ClosingFuture.Combiner that lets you use a lambda or method reference to combine three
ClosingFuture s. |
static class |
ClosingFuture.Combiner4<V1,V2,V3,V4>
A generic
ClosingFuture.Combiner that lets you use a lambda or method reference to combine four
ClosingFuture s. |
static class |
ClosingFuture.Combiner5<V1,V2,V3,V4,V5>
A generic
ClosingFuture.Combiner that lets you use a lambda or method reference to combine five
ClosingFuture s. |
static class |
ClosingFuture.DeferredCloser
An object that can capture objects to be closed later, when a
ClosingFuture pipeline is
done. |
static class |
ClosingFuture.Peeker
An object that can return the value of the
ClosingFuture s that are passed to whenAllComplete(Iterable) or whenAllSucceed(Iterable) . |
static class |
ClosingFuture.ValueAndCloser<V>
An object that holds the final result of an asynchronous
ClosingFuture operation and
allows the user to close all the closeable objects that were captured during it for later
closing. |
static interface |
ClosingFuture.ValueAndCloserConsumer<V>
Represents an operation that accepts a
ClosingFuture.ValueAndCloser for the last step in a ClosingFuture pipeline. |
Modifier and Type | Method and Description |
---|---|
boolean |
cancel(boolean mayInterruptIfRunning)
Attempts to cancel execution of this step.
|
<X extends Throwable> |
catching(Class<X> exceptionType,
ClosingFuture.ClosingFunction<? super X,? extends V> fallback,
Executor executor)
Returns a new
ClosingFuture pipeline step derived from this one by applying a function
to its exception if it is an instance of a given exception type. |
<X extends Throwable> |
catchingAsync(Class<X> exceptionType,
ClosingFuture.AsyncClosingFunction<? super X,? extends V> fallback,
Executor executor)
Returns a new
ClosingFuture pipeline step derived from this one by applying a function
that returns a ClosingFuture to its exception if it is an instance of a given exception
type. |
static <C extends Object & AutoCloseable> |
eventuallyClosing(ListenableFuture<C> future,
Executor closingExecutor)
Deprecated.
Creating
Future s of closeable types is dangerous in general because the
underlying value may never be closed if the Future is canceled after its operation
begins. Consider replacing code that creates ListenableFuture s of closeable types,
including those that pass them to this method, with submit(ClosingCallable,
Executor) in order to ensure that resources do not leak. Or, to start a pipeline with a
ListenableFuture that doesn't create values that should be closed, use from(com.google.common.util.concurrent.ListenableFuture<V>) . |
protected void |
finalize()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
|
FluentFuture<V> |
finishToFuture()
Marks this step as the last step in the
ClosingFuture pipeline. |
void |
finishToValueAndCloser(ClosingFuture.ValueAndCloserConsumer<? super V> consumer,
Executor executor)
Marks this step as the last step in the
ClosingFuture pipeline. |
static <V> ClosingFuture<V> |
from(ListenableFuture<V> future)
Starts a
ClosingFuture pipeline with a ListenableFuture . |
ListenableFuture<?> |
statusFuture()
Returns a future that finishes when this step does.
|
static <V> ClosingFuture<V> |
submit(ClosingFuture.ClosingCallable<V> callable,
Executor executor)
Starts a
ClosingFuture pipeline by submitting a callable block to an executor. |
static <V> ClosingFuture<V> |
submitAsync(ClosingFuture.AsyncClosingCallable<V> callable,
Executor executor)
Starts a
ClosingFuture pipeline by submitting a callable block to an executor. |
String |
toString()
Returns a string representation of the object.
|
<U> ClosingFuture<U> |
transform(ClosingFuture.ClosingFunction<? super V,U> function,
Executor executor)
Returns a new
ClosingFuture pipeline step derived from this one by applying a function
to its value. |
<U> ClosingFuture<U> |
transformAsync(ClosingFuture.AsyncClosingFunction<? super V,U> function,
Executor executor)
Returns a new
ClosingFuture pipeline step derived from this one by applying a function
that returns a ClosingFuture to its value. |
static ClosingFuture.Combiner |
whenAllComplete(ClosingFuture<?> future1,
ClosingFuture<?>... moreFutures)
Starts specifying how to combine
ClosingFuture s into a single pipeline. |
static ClosingFuture.Combiner |
whenAllComplete(Iterable<? extends ClosingFuture<?>> futures)
Starts specifying how to combine
ClosingFuture s into a single pipeline. |
static ClosingFuture.Combiner |
whenAllSucceed(ClosingFuture<?> future1,
ClosingFuture<?> future2,
ClosingFuture<?> future3,
ClosingFuture<?> future4,
ClosingFuture<?> future5,
ClosingFuture<?> future6,
ClosingFuture<?>... moreFutures)
Starts specifying how to combine
ClosingFuture s into a single pipeline, assuming they
all succeed. |
static <V1,V2> ClosingFuture.Combiner2<V1,V2> |
whenAllSucceed(ClosingFuture<V1> future1,
ClosingFuture<V2> future2)
Starts specifying how to combine two
ClosingFuture s into a single pipeline, assuming
they all succeed. |
static <V1,V2,V3> ClosingFuture.Combiner3<V1,V2,V3> |
whenAllSucceed(ClosingFuture<V1> future1,
ClosingFuture<V2> future2,
ClosingFuture<V3> future3)
Starts specifying how to combine three
ClosingFuture s into a single pipeline, assuming
they all succeed. |
static <V1,V2,V3,V4> |
whenAllSucceed(ClosingFuture<V1> future1,
ClosingFuture<V2> future2,
ClosingFuture<V3> future3,
ClosingFuture<V4> future4)
Starts specifying how to combine four
ClosingFuture s into a single pipeline, assuming
they all succeed. |
static <V1,V2,V3,V4,V5> |
whenAllSucceed(ClosingFuture<V1> future1,
ClosingFuture<V2> future2,
ClosingFuture<V3> future3,
ClosingFuture<V4> future4,
ClosingFuture<V5> future5)
Starts specifying how to combine five
ClosingFuture s into a single pipeline, assuming
they all succeed. |
static ClosingFuture.Combiner |
whenAllSucceed(Iterable<? extends ClosingFuture<?>> futures)
Starts specifying how to combine
ClosingFuture s into a single pipeline, assuming they
all succeed. |
static <V,U> ClosingFuture.AsyncClosingFunction<V,U> |
withoutCloser(AsyncFunction<V,U> function)
Returns an
ClosingFuture.AsyncClosingFunction that applies an AsyncFunction to an input,
ignoring the DeferredCloser and returning a ClosingFuture derived from the returned
ListenableFuture . |
public static <V> ClosingFuture<V> submit(ClosingFuture.ClosingCallable<V> callable, Executor executor)
ClosingFuture
pipeline by submitting a callable block to an executor.RejectedExecutionException
- if the task cannot be scheduled for
executionpublic static <V> ClosingFuture<V> submitAsync(ClosingFuture.AsyncClosingCallable<V> callable, Executor executor)
ClosingFuture
pipeline by submitting a callable block to an executor.RejectedExecutionException
- if the task cannot be scheduled for
executionpublic static <V> ClosingFuture<V> from(ListenableFuture<V> future)
ClosingFuture
pipeline with a ListenableFuture
.
future
's value will not be closed when the pipeline is done even if V
implements Closeable
. In order to start a pipeline with a value that will be closed
when the pipeline is done, use submit(ClosingCallable, Executor)
instead.
@Deprecated public static <C extends Object & AutoCloseable> ClosingFuture<C> eventuallyClosing(ListenableFuture<C> future, Executor closingExecutor)
Future
s of closeable types is dangerous in general because the
underlying value may never be closed if the Future
is canceled after its operation
begins. Consider replacing code that creates ListenableFuture
s of closeable types,
including those that pass them to this method, with submit(ClosingCallable,
Executor)
in order to ensure that resources do not leak. Or, to start a pipeline with a
ListenableFuture
that doesn't create values that should be closed, use from(com.google.common.util.concurrent.ListenableFuture<V>)
.ClosingFuture
pipeline with a ListenableFuture
.
If future
succeeds, its value will be closed (using closingExecutor)
when
the pipeline is done, even if the pipeline is canceled or fails.
Cancelling the pipeline will not cancel future
, so that the pipeline can access its
value in order to close it.
future
- the future to create the ClosingFuture
from. For discussion of the
future's result type C
, see DeferredCloser#eventuallyClose(Closeable,
Executor)
.closingExecutor
- the future's result will be closed on this executorpublic static ClosingFuture.Combiner whenAllComplete(Iterable<? extends ClosingFuture<?>> futures)
ClosingFuture
s into a single pipeline.IllegalStateException
- if a ClosingFuture
has already been derived from any of
the futures
, or if any has already been finishedpublic static ClosingFuture.Combiner whenAllComplete(ClosingFuture<?> future1, ClosingFuture<?>... moreFutures)
ClosingFuture
s into a single pipeline.IllegalStateException
- if a ClosingFuture
has already been derived from any of
the arguments, or if any has already been finishedpublic static ClosingFuture.Combiner whenAllSucceed(Iterable<? extends ClosingFuture<?>> futures)
ClosingFuture
s into a single pipeline, assuming they
all succeed. If any fail, the resulting pipeline will fail.IllegalStateException
- if a ClosingFuture
has already been derived from any of
the futures
, or if any has already been finishedpublic static <V1,V2> ClosingFuture.Combiner2<V1,V2> whenAllSucceed(ClosingFuture<V1> future1, ClosingFuture<V2> future2)
ClosingFuture
s into a single pipeline, assuming
they all succeed. If any fail, the resulting pipeline will fail.
Calling this method allows you to use lambdas or method references typed with the types of
the input ClosingFuture
s.
IllegalStateException
- if a ClosingFuture
has already been derived from any of
the arguments, or if any has already been finishedpublic static <V1,V2,V3> ClosingFuture.Combiner3<V1,V2,V3> whenAllSucceed(ClosingFuture<V1> future1, ClosingFuture<V2> future2, ClosingFuture<V3> future3)
ClosingFuture
s into a single pipeline, assuming
they all succeed. If any fail, the resulting pipeline will fail.
Calling this method allows you to use lambdas or method references typed with the types of
the input ClosingFuture
s.
IllegalStateException
- if a ClosingFuture
has already been derived from any of
the arguments, or if any has already been finishedpublic static <V1,V2,V3,V4> ClosingFuture.Combiner4<V1,V2,V3,V4> whenAllSucceed(ClosingFuture<V1> future1, ClosingFuture<V2> future2, ClosingFuture<V3> future3, ClosingFuture<V4> future4)
ClosingFuture
s into a single pipeline, assuming
they all succeed. If any fail, the resulting pipeline will fail.
Calling this method allows you to use lambdas or method references typed with the types of
the input ClosingFuture
s.
IllegalStateException
- if a ClosingFuture
has already been derived from any of
the arguments, or if any has already been finishedpublic static <V1,V2,V3,V4,V5> ClosingFuture.Combiner5<V1,V2,V3,V4,V5> whenAllSucceed(ClosingFuture<V1> future1, ClosingFuture<V2> future2, ClosingFuture<V3> future3, ClosingFuture<V4> future4, ClosingFuture<V5> future5)
ClosingFuture
s into a single pipeline, assuming
they all succeed. If any fail, the resulting pipeline will fail.
Calling this method allows you to use lambdas or method references typed with the types of
the input ClosingFuture
s.
IllegalStateException
- if a ClosingFuture
has already been derived from any of
the arguments, or if any has already been finishedpublic static ClosingFuture.Combiner whenAllSucceed(ClosingFuture<?> future1, ClosingFuture<?> future2, ClosingFuture<?> future3, ClosingFuture<?> future4, ClosingFuture<?> future5, ClosingFuture<?> future6, ClosingFuture<?>... moreFutures)
ClosingFuture
s into a single pipeline, assuming they
all succeed. If any fail, the resulting pipeline will fail.IllegalStateException
- if a ClosingFuture
has already been derived from any of
the arguments, or if any has already been finishedpublic ListenableFuture<?> statusFuture()
get()
on the returned
future returns null
if the step is successful or throws the same exception that would
be thrown by calling finishToFuture().get()
if this were the last step. Calling cancel()
on the returned future has no effect on the ClosingFuture
pipeline.
statusFuture
differs from most methods on ClosingFuture
: You can make calls
to statusFuture
in addition to the call you make to finishToFuture()
or
a derivation method on the same instance. This is important because calling statusFuture
alone does not provide a way to close the pipeline.
public <U> ClosingFuture<U> transform(ClosingFuture.ClosingFunction<? super V,U> function, Executor executor)
ClosingFuture
pipeline step derived from this one by applying a function
to its value. The function can use a ClosingFuture.DeferredCloser
to capture objects to be closed
when the pipeline is done.
If this ClosingFuture
fails, the function will not be called, and the derived ClosingFuture
will be equivalent to this one.
If the function throws an exception, that exception is used as the result of the derived
ClosingFuture
.
Example usage:
ClosingFuture<List<Row>> rowsFuture =
queryFuture.transform((closer, result) -> result.getRows(), executor);
When selecting an executor, note that directExecutor
is dangerous in some cases. See
the discussion in the ListenableFuture.addListener(java.lang.Runnable, java.util.concurrent.Executor)
documentation. All its warnings
about heavyweight listeners are also applicable to heavyweight functions passed to this method.
After calling this method, you may not call finishToFuture()
, finishToValueAndCloser(ValueAndCloserConsumer, Executor)
, or any other derivation method on
this ClosingFuture
.
function
- transforms the value of this step to the value of the derived stepexecutor
- executor to run the function inIllegalStateException
- if a ClosingFuture
has already been derived from this
one, or if this ClosingFuture
has already been finishedpublic <U> ClosingFuture<U> transformAsync(ClosingFuture.AsyncClosingFunction<? super V,U> function, Executor executor)
ClosingFuture
pipeline step derived from this one by applying a function
that returns a ClosingFuture
to its value. The function can use a ClosingFuture.DeferredCloser
to capture objects to be closed when the pipeline is done (other than those
captured by the returned ClosingFuture
).
If this ClosingFuture
succeeds, the derived one will be equivalent to the one
returned by the function.
If this ClosingFuture
fails, the function will not be called, and the derived ClosingFuture
will be equivalent to this one.
If the function throws an exception, that exception is used as the result of the derived
ClosingFuture
. But if the exception is thrown after the function creates a ClosingFuture
, then none of the closeable objects in that ClosingFuture
will be
closed.
Usage guidelines for this method:
ListenableFuture
or a
ClosingFuture
. If possible, prefer calling transform(ClosingFunction,
Executor)
instead, with a function that returns the next value directly.
closer.eventuallyClose()
for every closeable object this step creates in order to capture it for later closing.
ClosingFuture
. To turn a ListenableFuture
into a ClosingFuture
call from(ListenableFuture)
.
ListenableFuture
to return a ClosingFuture
by wrapping it with a call to
withoutCloser(AsyncFunction)
Example usage:
// Result.getRowsClosingFuture() returns a ClosingFuture.
ClosingFuture<List<Row>> rowsFuture =
queryFuture.transformAsync((closer, result) -> result.getRowsClosingFuture(), executor);
// Result.writeRowsToOutputStreamFuture() returns a ListenableFuture that resolves to the
// number of written rows. openOutputFile() returns a FileOutputStream (which implements
// Closeable).
ClosingFuture<Integer> rowsFuture2 =
queryFuture.transformAsync(
(closer, result) -> {
FileOutputStream fos = closer.eventuallyClose(openOutputFile(), closingExecutor);
return ClosingFuture.from(result.writeRowsToOutputStreamFuture(fos));
},
executor);
// Result.getRowsFuture() returns a ListenableFuture (no new closeables are created).
ClosingFuture<List<Row>> rowsFuture3 =
queryFuture.transformAsync(withoutCloser(Result::getRowsFuture), executor);
When selecting an executor, note that directExecutor
is dangerous in some cases. See
the discussion in the ListenableFuture.addListener(java.lang.Runnable, java.util.concurrent.Executor)
documentation. All its warnings
about heavyweight listeners are also applicable to heavyweight functions passed to this method.
(Specifically, directExecutor
functions should avoid heavyweight operations inside
AsyncClosingFunction.apply
. Any heavyweight operations should occur in other threads
responsible for completing the returned ClosingFuture
.)
After calling this method, you may not call finishToFuture()
, finishToValueAndCloser(ValueAndCloserConsumer, Executor)
, or any other derivation method on
this ClosingFuture
.
function
- transforms the value of this step to a ClosingFuture
with the value of
the derived stepexecutor
- executor to run the function inIllegalStateException
- if a ClosingFuture
has already been derived from this
one, or if this ClosingFuture
has already been finishedpublic static <V,U> ClosingFuture.AsyncClosingFunction<V,U> withoutCloser(AsyncFunction<V,U> function)
ClosingFuture.AsyncClosingFunction
that applies an AsyncFunction
to an input,
ignoring the DeferredCloser and returning a ClosingFuture
derived from the returned
ListenableFuture
.
Use this method to pass a transformation to transformAsync(AsyncClosingFunction,
Executor)
or to catchingAsync(Class, AsyncClosingFunction, Executor)
as long as it
meets these conditions:
Closeable
objects by calling DeferredCloser#eventuallyClose(Closeable, Executor)
.
ListenableFuture
.
Example usage:
// Result.getRowsFuture() returns a ListenableFuture.
ClosingFuture<List<Row>> rowsFuture =
queryFuture.transformAsync(withoutCloser(Result::getRowsFuture), executor);
function
- transforms the value of a ClosingFuture
step to a ListenableFuture
with the value of a derived steppublic <X extends Throwable> ClosingFuture<V> catching(Class<X> exceptionType, ClosingFuture.ClosingFunction<? super X,? extends V> fallback, Executor executor)
ClosingFuture
pipeline step derived from this one by applying a function
to its exception if it is an instance of a given exception type. The function can use a ClosingFuture.DeferredCloser
to capture objects to be closed when the pipeline is done.
If this ClosingFuture
succeeds or fails with a different exception type, the
function will not be called, and the derived ClosingFuture
will be equivalent to this
one.
If the function throws an exception, that exception is used as the result of the derived
ClosingFuture
.
Example usage:
ClosingFuture<QueryResult> queryFuture =
queryFuture.catching(
QueryException.class, (closer, x) -> Query.emptyQueryResult(), executor);
When selecting an executor, note that directExecutor
is dangerous in some cases. See
the discussion in the ListenableFuture.addListener(java.lang.Runnable, java.util.concurrent.Executor)
documentation. All its warnings
about heavyweight listeners are also applicable to heavyweight functions passed to this method.
After calling this method, you may not call finishToFuture()
, finishToValueAndCloser(ValueAndCloserConsumer, Executor)
, or any other derivation method on
this ClosingFuture
.
exceptionType
- the exception type that triggers use of fallback
. The exception
type is matched against this step's exception. "This step's exception" means the cause of
the ExecutionException
thrown by Future.get()
on the Future
underlying this step or, if get()
throws a different kind of exception, that
exception itself. To avoid hiding bugs and other unrecoverable errors, callers should
prefer more specific types, avoiding Throwable.class
in particular.fallback
- the function to be called if this step fails with the expected exception type.
The function's argument is this step's exception. "This step's exception" means the cause
of the ExecutionException
thrown by Future.get()
on the Future
underlying this step or, if get()
throws a different kind of exception, that
exception itself.executor
- the executor that runs fallback
if the input failspublic <X extends Throwable> ClosingFuture<V> catchingAsync(Class<X> exceptionType, ClosingFuture.AsyncClosingFunction<? super X,? extends V> fallback, Executor executor)
ClosingFuture
pipeline step derived from this one by applying a function
that returns a ClosingFuture
to its exception if it is an instance of a given exception
type. The function can use a ClosingFuture.DeferredCloser
to capture objects to be closed when the
pipeline is done (other than those captured by the returned ClosingFuture
).
If this ClosingFuture
fails with an exception of the given type, the derived ClosingFuture
will be equivalent to the one returned by the function.
If this ClosingFuture
succeeds or fails with a different exception type, the
function will not be called, and the derived ClosingFuture
will be equivalent to this
one.
If the function throws an exception, that exception is used as the result of the derived
ClosingFuture
. But if the exception is thrown after the function creates a ClosingFuture
, then none of the closeable objects in that ClosingFuture
will be
closed.
Usage guidelines for this method:
ListenableFuture
or a
ClosingFuture
. If possible, prefer calling catching(Class,
ClosingFunction, Executor)
instead, with a function that returns the next value
directly.
closer.eventuallyClose()
for every closeable object this step creates in order to capture it for later closing.
ClosingFuture
. To turn a ListenableFuture
into a ClosingFuture
call from(ListenableFuture)
.
ListenableFuture
to return a ClosingFuture
by wrapping it with a call to
withoutCloser(AsyncFunction)
Example usage:
// Fall back to a secondary input stream in case of IOException.
ClosingFuture<InputStream> inputFuture =
firstInputFuture.catchingAsync(
IOException.class, (closer, x) -> secondaryInputStreamClosingFuture(), executor);
}
When selecting an executor, note that directExecutor
is dangerous in some cases. See
the discussion in the ListenableFuture.addListener(java.lang.Runnable, java.util.concurrent.Executor)
documentation. All its warnings
about heavyweight listeners are also applicable to heavyweight functions passed to this method.
(Specifically, directExecutor
functions should avoid heavyweight operations inside
AsyncClosingFunction.apply
. Any heavyweight operations should occur in other threads
responsible for completing the returned ClosingFuture
.)
After calling this method, you may not call finishToFuture()
, finishToValueAndCloser(ValueAndCloserConsumer, Executor)
, or any other derivation method on
this ClosingFuture
.
exceptionType
- the exception type that triggers use of fallback
. The exception
type is matched against this step's exception. "This step's exception" means the cause of
the ExecutionException
thrown by Future.get()
on the Future
underlying this step or, if get()
throws a different kind of exception, that
exception itself. To avoid hiding bugs and other unrecoverable errors, callers should
prefer more specific types, avoiding Throwable.class
in particular.fallback
- the function to be called if this step fails with the expected exception type.
The function's argument is this step's exception. "This step's exception" means the cause
of the ExecutionException
thrown by Future.get()
on the Future
underlying this step or, if get()
throws a different kind of exception, that
exception itself.executor
- the executor that runs fallback
if the input failspublic FluentFuture<V> finishToFuture()
ClosingFuture
pipeline.
The returned Future
is completed when the pipeline's computation completes, or when
the pipeline is cancelled.
All objects the pipeline has captured for closing will begin to be closed asynchronously
after the returned Future
is done: the future completes before closing starts,
rather than once it has finished.
After calling this method, you may not call finishToValueAndCloser(ValueAndCloserConsumer, Executor)
, this method, or any other
derivation method on this ClosingFuture
.
Future
that represents the final value or exception of the pipelinepublic void finishToValueAndCloser(ClosingFuture.ValueAndCloserConsumer<? super V> consumer, Executor executor)
ClosingFuture
pipeline. When this step is done,
receiver
will be called with an object that contains the result of the operation. The
receiver can store the ClosingFuture.ValueAndCloser
outside the receiver for later synchronous use.
After calling this method, you may not call finishToFuture()
, this method again, or
any other derivation method on this ClosingFuture
.
consumer
- a callback whose method will be called (using executor
) when this
operation is done@CanIgnoreReturnValue public boolean cancel(boolean mayInterruptIfRunning)
cancel
is called, this step should never
run.
If successful, causes the objects captured by this step (if already started) and its input
step(s) for later closing to be closed on their respective Executor
s. If any such calls
specified MoreExecutors.directExecutor()
, those objects will be closed synchronously.
mayInterruptIfRunning
- true
if the thread executing this task should be
interrupted; otherwise, in-progress tasks are allowed to complete, but the step will be
cancelled regardlessfalse
if the step could not be cancelled, typically because it has already
completed normally; true
otherwisepublic String toString()
java.lang.Object
toString
method returns a string that
"textually represents" this object. The result should
be a concise but informative representation that is easy for a
person to read.
It is recommended that all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the
object is an instance, the at-sign character `@
', and
the unsigned hexadecimal representation of the hash code of the
object. In other words, this method returns a string equal to the
value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
protected void finalize()
java.lang.Object
finalize
method to dispose of
system resources or to perform other cleanup.
The general contract of finalize
is that it is invoked
if and when the Java™ virtual
machine has determined that there is no longer any
means by which this object can be accessed by any thread that has
not yet died, except as a result of an action taken by the
finalization of some other object or class which is ready to be
finalized. The finalize
method may take any action, including
making this object available again to other threads; the usual purpose
of finalize
, however, is to perform cleanup actions before
the object is irrevocably discarded. For example, the finalize method
for an object that represents an input/output connection might perform
explicit I/O transactions to break the connection before the object is
permanently discarded.
The finalize
method of class Object
performs no
special action; it simply returns normally. Subclasses of
Object
may override this definition.
The Java programming language does not guarantee which thread will
invoke the finalize
method for any given object. It is
guaranteed, however, that the thread that invokes finalize will not
be holding any user-visible synchronization locks when finalize is
invoked. If an uncaught exception is thrown by the finalize method,
the exception is ignored and finalization of that object terminates.
After the finalize
method has been invoked for an object, no
further action is taken until the Java virtual machine has again
determined that there is no longer any means by which this object can
be accessed by any thread that has not yet died, including possible
actions by other objects or classes which are ready to be finalized,
at which point the object may be discarded.
The finalize
method is never invoked more than once by a Java
virtual machine for any given object.
Any exception thrown by the finalize
method causes
the finalization of this object to be halted, but is otherwise
ignored.
finalize
in class Object
WeakReference
,
PhantomReference
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