com.google.jstestdriver.requesthandlers.GatewayConfiguration Maven / Gradle / Ivy

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// Copyright 2011 Google Inc. All Rights Reserved.
package com.google.jstestdriver.requesthandlers;

import static com.google.jstestdriver.requesthandlers.HttpMethod.ANY;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.Singleton;
import com.google.jstestdriver.server.gateway.GatewayRequestHandler;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;

/**
 * An object that maintains a mapping between {@link RequestMatcher}s and
 * initialized {@link GatewayRequestHandler}s pointing to various hosts so that the
 * {@link RequestDispatcher} may instantiate {@link GatewayRequestHandler}s on
 * demand.
 *
 * @author [email protected] (Robert Dionne)
 */
public class GatewayConfiguration {

  private static final Logger logger =
      LoggerFactory.getLogger(GatewayConfiguration.class);

  /**
   * JSON key identifying the {@link RequestMatcher} pattern.
   */
  public static final String MATCHER = "matcher";

  /**
   * JSON key identifying the host path.
   */
  public static final String SERVER = "server";

  private final GatewayRequestHandler.Factory gatewayFactory;

  private JsonArray gatewayConfig = new JsonArray();
  private List matchers;
  private Map destinations;

  /**
   * Constructs a {@link GatewayConfiguration}. {@link GatewayConfiguration} is
   * bound to the {@link Singleton} scope.
   * @param gatewayFactory A Guice {@link Provider} of {@link GatewayRequestHandler}s.
   */
  @Inject
  public GatewayConfiguration(GatewayRequestHandler.Factory gatewayFactory) {
    this.gatewayFactory = gatewayFactory;
    clearConfiguration();
  }

  /**
   * @return A {@link List} of {@link RequestMatcher}s to hand off to the
   * {@link RequestDispatcher} for gatewaying matching requests to various hosts.
   */
  public synchronized List getMatchers() {
    return matchers;
  }

  /**
   * Instantiates a {@link GatewayRequestHandler} to gateway the current request
   * along to the matching host.
   * @param matcher The {@link RequestMatcher} that matches the current request.
   * @return A suitable {@link RequestHandler}.
   */
  public synchronized RequestHandler getRequestHandler(RequestMatcher matcher) {
    String destination = destinations.get(matcher);
    return destination == null ? new NullRequestHandler()
        : gatewayFactory.create(destination, matcher.getPrefix());
  }

  public synchronized JsonArray getGatewayConfig() {
    return gatewayConfig;
  }

  /**
   * Updates this {@link GatewayConfiguration} given the new {@code configuration}
   * encoded as a {@link JsonObject} by discarding previously initialized
   * {@link GatewayRequestHandler}s and instantiating new ones with new hosts.
   * @param configuration A {@link JsonObject} specifying a new configuration.
   * @throws ServletException If the new servlets fail to initialize.
   */
  public synchronized void updateConfiguration(JsonArray configuration)
      throws ServletException {
    gatewayConfig = configuration;
    ImmutableList.Builder listBuilder = ImmutableList.builder();
    ImmutableMap.Builder mapBuilder = ImmutableMap.builder();
    for (JsonElement element : configuration) {
      JsonObject entry = element.getAsJsonObject();
      RequestMatcher matcher =
          new RequestMatcher(ANY, entry.get(MATCHER).getAsString());
      listBuilder.add(matcher);
      mapBuilder.put(matcher, entry.get(SERVER).getAsString());
    }
    this.matchers = listBuilder.build();
    this.destinations = mapBuilder.build();
  }

  /**
   * Empties the mapping of {@link RequestMatcher}s to
   * {@link GatewayRequestHandler}s.
   */
  public synchronized void clearConfiguration() {
    this.matchers = ImmutableList.of();
    this.destinations = ImmutableMap.of();
  }
}