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package org.glassfish.jersey.process.internal;
import java.util.function.Function;
/**
* Data processing stage that can be used to create dynamic data processing chains.
* <p>
* An stage is a stateless data processing unit that returns a
* {@link Continuation processing continuation}.
* </p>
*
* @param <DATA> processed data type.
* @author Marek Potociar (marek.potociar at oracle.com)
*/
public interface Stage<DATA> {
/**
* Data processing stage continuation.
* <p>
* A continuation of a processing stage is a processing result represented by an
* ({@link #hasNext() optional}) stage that should be invoked {@link #next() next}
* and the processed data {@link #result() result}.
* </p>
*
* @param <DATA> processed data type.
*/
public static final class Continuation<DATA> {
private final DATA result;
private final Stage<DATA> next;
/**
* Create a new continuation instance.
*
* @param result processed data.
* @param next next processing stage.
*/
Continuation(final DATA result, final Stage<DATA> next) {
this.result = result;
this.next = next;
}
/**
* Create a continuation from the processed data result and the stage
* to be invoked next.
*
* @param <DATA> processed data type.
* @param result data processing result.
* @param next stage to be invoked next.
* @return a continuation with the supplied stage to be invoked
* {@link Stage.Continuation#next() next} in the processing chain
* and the supplied processing result.
*/
public static <DATA> Continuation<DATA> of(final DATA result, Stage<DATA> next) {
return new Continuation<DATA>(result, next);
}
/**
* Create a terminal continuation from the processed data result.
*
* @param <DATA> processed data type.
* @param result data processing result.
* @return terminal continuation with no {@link Stage.Continuation#next() next}
* stage in the processing chain and the supplied processing result.
*/
public static <DATA> Continuation<DATA> of(final DATA result) {
return new Continuation<DATA>(result, null);
}
/**
* Get the data processing result.
*
* @return data processing result.
*/
public DATA result() {
return result;
}
/**
* Get the stage to be invoked next or {@code null} if no next stage is
* {@link #hasNext() present}.
*
* @return the stage to be invoked next or {@code null} if not present.
*/
public Stage<DATA> next() {
return next;
}
/**
* Check if there is a next stage present in the continuation.
* <p>
* The absence of a next stage in the continuation indicates that the data processing
* reached a terminal stage and the {@link #result() result} of the continuation represents
* the final result of the whole processing chain.
* </p>
*
* @return {@code true} if there is a next stage present in the continuation,
* {@code false} otherwise.
*/
public boolean hasNext() {
return next != null;
}
}
/**
* Linear stage chain builder.
*
* @param <DATA> processed data type.
*/
public static interface Builder<DATA> {
/**
* Add a transformation function as a next stage to the stage chain.
* <p>
* The order of the {@code to(...)} method invocations matches the order
* of the stage execution at runtime.
* </p>
*
* @param transformation a transformation function to be added as a next
* stage to the stage chain.
* @return updated builder instance.
*/
public Builder<DATA> to(Function<DATA, DATA> transformation);
/**
* Add a new {@link ChainableStage chainable stage} as a next stage to the
* stage chain.
* <p>
* The order of the {@code to(...)} method invocations matches the order
* of the stage execution at runtime.
* A subsequent call to a {@code to(...)} method will automatically invoke the
* {@link ChainableStage#setDefaultNext(Stage)} method on the chainable
* stage.
* </p>
*
* @param stage a chainable stage to be added as a next
* stage to the stage chain.
* @return updated builder instance.
*/
public Builder<DATA> to(ChainableStage<DATA> stage);
/**
* Build a stage chain.
*
* @return built acceptor chain.
*/
public Stage<DATA> build();
/**
* Add a terminal stage to the stage chain and build the chain.
*
* @param terminal last stage to be added to the stage chain.
* @return built stage chain.
*/
public Stage<DATA> build(Stage<DATA> terminal);
}
/**
* Performs a data processing task and returns the processed data together with
* a {@link Continuation processing continuation}.
*
* @param data data to be transformed.
* @return a processing continuation.
*/
public Continuation<DATA> apply(DATA data);
}