An Async I/O proposal for Servlet 3.x spec.

1. Asynchronous I/O
for Servlet 3.0
Jeanfrancois Arcand
Senior Staff Engineer
Sun Microsystems

2. Goal JGD
• Bring Asynchronous I/O to Servlet without
exposing low level I/O details
• New classes:
> ServletFuture
> ServletAsyncHandler
> ServletRequestChannel
> ServletResponseChannel
> ReadFuture
> WriteFuture
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3. ServletFuture JGD
• A Future representing the result of an
asynchronous I/O operation.
• In addition to the methods defined by the
Future interface, a ServletFuture allows
for the attachment of a single arbitrary
object.
• The object can be used to associate
application-specific data or context
required when consuming the result of the
I/O operation.
• This is important for cases where the
same ServletAsyncHandler is used to
consume the result of several I/O
operations.
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4. ServletIoFuture JGD
boolean cancel(boolean mayInterruptIfRunning)
A attachment()
A attach(A attachment)
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5. ServletAsyncHandler JGD
• A handler for consuming the result of an
asynchronous I/O operation.
• The asynchronous
ServletRequestChannel.read or
ServletResponseChannel.write defined in
this package allow a ServletAsyncHandler
to be specified yo consume the result of
an asynchronous operation.
• When an operation completes the
handler's completed method is invoked
with the result.
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6. ServletAsyncHandler JGD
void completed(ServletIoFuture<T,A> result)
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7. ServletRequestChannel JGD
• An asynchronous channel for read
stream-oriented operations.
• Allow synchronous and asynchronous
read operations
• From a Class definition, the read
operation will convert the request body
into an instance of that Class definition.
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8. ServletRequestChannel JGD
<T,A> ReadFuture<T,A> read
(java.lang.Class<T> clazz,
A attachment,
ServletAsyncHandler<? super T,A>
handler)
<T,A> ReadFuture<T,A> read
(java.lang.Class<T> clazz,
long timeout,
TimeUnit unit,
A attachment,
ServletAsyncHandler<? super T,A>
handler)
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9. Example 1: Asynchronous Read JGD
// Asynchronous Read
// The request is automatically suspended when the getChannel() is invoked.
// See Example 3 for a scenario when the request is not explicitly suspended.
ServletRequestChannel channel = servletRequest.getChannel();
ReadFuture ioFuture = channel.read(Map.class,30,TimeUnits.SECONDS, null,
new ServletAsyncHandler<ReadFuture<Map,Void>){
public void completed(ReadFuture<Map,Void> result){
Map map = result.getContent();
}
});
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10. Example 2: Synchronous Read JGD
// Synchronous Read
ServletRequestChannel channel = servletRequest.getChannel();
ReadFuture ioFuture = channel.read(Map.class);
// Or ReadFuture ioFuture = channel.read(Map.class,null,null);
ioFuture.get(30,TimeUnits.SECONDS);
Map map = ioFuture.getContent() ;
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11. Example 3: Suspendable Request JGD
// Asynchronous Read
servletRequest.suspend();
ServletRequestChannel channel = servletRequest.getChannel();
ReadFuture ioFuture = channel.read(
Map.class,30,TimeUnits.SECONDS, servletRequest,
new ServletAsyncHandler<ReadFuture<Map,ServletRequest>){
public void completed(ReadFuture<Map,ServletRequest> result){
Map map = result.getContent();
result.attachment().resume();
}
});
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12. ServletResponseChannel JGD
• An asynchronous channel for write
stream-oriented operations.
• Allow synchronous and asynchronous
write operations
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13. ServletResponseChannel JGD
<A> WriteFuture<Integer> write
(Object object,
A attachment,
ServletAsyncHandler<Integer,A> handler)
<A> WriteFuture<Integer> write
(Object object,
long timeout,
TimeUnit unit,
A attachment,
ServletAsyncHandler<Integer,A> handler)
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14. Example 4: Asynchronous Write JGD
// Asynchronous Write
// The request is automatically suspended when the getChannel() is invoked.
// See Example 6 for a scenario when the request is not explicitly suspended.
ServletResponseChannel channel = servletResponse.getChannel();
WriteFuture ioFuture = channel.write(“Hello”,30,TimeUnits.SECONDS, null,
new ServletAsyncHandler<WriteFuture<Integer,Void>){
public void completed(WriteFuture<Integer,Void> result){
System.out.println(“Bytes Written: “ + result.get());
}
});
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15. Example 5: Asynchronous Write JGD
// Asynchronous Write
ServletResponseChannel channel = servletResponse.getChannel();
WriteFuture ioFuture = channel.write(“Hello”,30,TimeUnits.SECONDS, null,
new ServletAsyncHandler<WriteFuture<Integer,Void>){
public void completed(WriteFuture<Integer,Void> result){
System.out.println(“Bytes Written: “ + result.get());
}
});
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16. Example 6: Synchronous Write JGD
// Asynchronous Write
ServletResponseChannel channel = servletResponse.getChannel();
WriteIoFuture ioFuture = channel.write(“Hello”);
ioFuture.get(30,TimeUnits.SECONDS);
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17. Example 2: Suspendable Request JGD
// Asynchronous Read
servletRequest.suspend();
ServletResponseChannel channel = servletResponse.getChannel();
WriteIoFuture ioFuture = channel.write(
“Hello”,30,TimeUnits.SECONDS, servletRequest, new
ServletAsynchronousIoHandler<WriteIoFuture<Integer,ServletRequest>){
public void completed(WriteIoFuture<Integer,ServletRequest> result){
result.attachment().resume();
}
});
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18. Summary JGD
• Simple API.
• No buffering of data
• API can be used synchronously and
asynchronously.
• Easy to implement.
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19. jeanfrancois.arcand@sun.com