org.glassfish.jersey.process.internal.Stages Maven / Gradle / Ivy
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package org.glassfish.jersey.process.internal;
import java.util.Deque;
import java.util.LinkedList;
import org.glassfish.jersey.process.Inflector;
import com.google.common.base.Function;
/**
* A stage-related collection of utility methods.
*
* @author Marek Potociar (marek.potociar at oracle.com)
*/
public final class Stages {
/**
* Prevents instantiation.
*/
private Stages() {
}
/**
* Creates a terminal {@link Stage} that implements {@link Inflecting}
* interface and returns the provided {@link Inflector} instance
* when the {@link Inflecting#inflector()} method is called.
*
* @param inflector a request to response transformation to be wrapped in
* a stage.
* @return a stage that wraps the supplied {@code Inflector}.
*/
@SuppressWarnings("unchecked")
public static Stage asStage(final Inflector inflector) {
return new InflectingStage(inflector);
}
private static class InflectingStage implements Stage, Inflecting {
private final Inflector inflector;
public InflectingStage(Inflector inflector) {
this.inflector = inflector;
}
@Override
public Inflector inflector() {
return inflector;
}
@Override
public Stage.Continuation apply(DATA request) {
return Continuation.of(request);
}
}
/**
* (Optionally) extracts an {@link Inflector inflector} from a processing stage,
* provided the stage implements {@link Inflecting} interface. Otherwise method
* returns {@code null}.
*
* @param data type transformable by the stage and returned inflector.
* @param type of result produced by a successful inflector data transformation.
* @param stage a stage to extract the inflector from.
* @return extracted inflector if present, {@code null} otherwise.
*/
@SuppressWarnings("unchecked")
public static Inflector extractInflector(Object stage) {
if (stage instanceof Inflecting) {
return ((Inflecting) stage).inflector();
}
return null;
}
/**
* Start building a stage chain.
*
* @param transformation root transformation function.
* @return linear accepting chain builder.
*/
public static Stage.Builder chain(Function transformation) {
return new StageChainBuilder(transformation);
}
/**
* Start building a stage chain.
*
* @param rootStage root {@link ChainableStage chainable linear stage}.
* @return linear accepting chain builder.
*/
public static Stage.Builder chain(ChainableStage rootStage) {
return new StageChainBuilder(rootStage);
}
private static class StageChainBuilder implements Stage.Builder {
private final Deque> transformations = new LinkedList>();
private Stage rootStage;
private ChainableStage lastStage;
private StageChainBuilder(Function transformation) {
transformations.push(transformation);
}
private StageChainBuilder(ChainableStage rootStage) {
this.rootStage = rootStage;
this.lastStage = rootStage;
}
@Override
public Stage.Builder to(Function transformation) {
transformations.push(transformation);
return this;
}
@Override
public Stage.Builder to(final ChainableStage stage) {
addTailStage(stage);
lastStage = stage;
return this;
}
private void addTailStage(Stage lastStage) {
Stage tail = lastStage;
if (!transformations.isEmpty()) {
tail = convertTransformations(lastStage);
}
if (rootStage != null) {
this.lastStage.setDefaultNext(tail);
} else {
rootStage = tail;
}
}
@Override
public Stage build(Stage stage) {
addTailStage(stage);
return rootStage;
}
@Override
public Stage build() {
return build(null);
}
private Stage convertTransformations(Stage successor) {
Stage stage;
if (successor == null) {
stage = new LinkedStage(transformations.poll());
} else {
stage = new LinkedStage(transformations.poll(), successor);
}
Function t;
while ((t = transformations.poll()) != null) {
stage = new LinkedStage(t, stage);
}
return stage;
}
}
static class LinkedStage implements Stage {
private final Stage nextStage;
private final Function transformation;
/**
* Create a new stage that will return the supplied stage in the
* continuation.
*
* @param transformation Request transformation function to be applied in the stage.
* @param nextStage next stage returned in the continuation.
*/
public LinkedStage(Function transformation, Stage nextStage) {
this.nextStage = nextStage;
this.transformation = transformation;
}
/**
* Create a new terminal stage .
*
* @param transformation Request transformation function to be applied in the stage.
*/
public LinkedStage(Function transformation) {
this(transformation, null);
}
@Override
public Stage.Continuation apply(DATA data) {
return Continuation.of(transformation.apply(data), nextStage);
}
}
}