Package org.forgerock.util.promise

package org.forgerock.util.promise

An implementation of the Promise API in Java. Promises provide a simple API for chaining together asynchronous tasks and result transformation.

Example using CREST:

 final ConnectionFactory server = getConnectionFactory();
 final AtomicReference<Connection> connectionHolder = new AtomicReference<Connection>();
 final Promise<Resource, ResourceException> promise = server.getConnectionAsync()
     .thenAsync(new AsyncFunction<Connection, Resource, ResourceException>() {
         // Read resource.
         public Promise<Resource, ResourceException> apply(final Connection connection)
                 throws ResourceException {
             connectionHolder.set(connection); // Save connection for later.
             return connection.readAsync(ctx(), Requests.newReadRequest("users/1"));
         }
     }).thenAsync(new AsyncFunction<Resource, Resource, ResourceException>() {
         // Update resource.
         public Promise<Resource, ResourceException> apply(final Resource user) throws ResourceException {
             return connectionHolder.get().updateAsync(ctx(),
                     Requests.newUpdateRequest("users/1", userAliceWithIdAndRev(1, 1)));
         }
     }).then(new SuccessHandler<Resource>() {
         // Check updated resource.
         public void handleResult(final Resource user) {
             // Update successful!
         }
     }).thenAlways(new Runnable() {
         // Close the connection.
         public void run() {
             final Connection connection = connectionHolder.get();
             if (connection != null) {
                 connection.close();
             }
         }
     });
 

See Also:

• Promises/A+

Related Packages

Package	Description
org.forgerock.util	Provides common interfaces and classes.

Class	Description
ExceptionHandler<E>	A completion handler for consuming exceptions which occur during the execution of asynchronous tasks.
NeverThrowsException	The NeverThrowsException class is an uninstantiable placeholder exception which should be used for indicating that a Function or AsyncFunction never throws an exception (i.e.
Promise<V,E extends Exception>	A Promise represents the result of an asynchronous task.
PromiseImpl<V,E extends Exception>	An implementation of Promise which can be used as is, or as the basis for more complex asynchronous behavior.
Promises	Utility methods for creating and composing Promises.
Promises.IterateOverBuilder<V,E extends Exception>	IterateOverBuilder provides a mechanism for iterating over a stream or iterable of promise suppliers in search of the first to match the supplied predicate.
Promises.Results	Ordered list of joined asynchronous results.
ResultHandler<V>	A completion handler for consuming the results of asynchronous tasks.
RuntimeExceptionHandler	A completion handler for consuming runtime exceptions which occur during the execution of asynchronous tasks.