react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/JSBundleLoader.java

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.react.bridge;

import android.content.Context;

/**
 * A class that stores JS bundle information and allows {@link CatalystInstance} to load a correct
 * bundle through {@link ReactBridge}.
 */
public abstract class JSBundleLoader {

  /**
   * This loader is recommended one for release version of your app. In that case local JS executor
   * should be used. JS bundle will be read from assets directory in native code to save on passing
   * large strings from java to native memory.
   */
  public static JSBundleLoader createFileLoader(
      final Context context,
      final String fileName) {
    return new JSBundleLoader() {
      @Override
      public void loadScript(ReactBridge bridge) {
        if (fileName.startsWith("assets://")) {
          bridge.loadScriptFromAssets(context.getAssets(), fileName.replaceFirst("assets://", ""));
        } else {
          bridge.loadScriptFromFile(fileName, "file://" + fileName);
        }
      }

      @Override
      public String getSourceUrl() {
        return (fileName.startsWith("assets://") ? "" : "file://") + fileName;
      }
    };
  }

  /**
   * This loader is used when bundle gets reloaded from dev server. In that case loader expect JS
   * bundle to be prefetched and stored in local file. We do that to avoid passing large strings
   * between java and native code and avoid allocating memory in java to fit whole JS bundle in it.
   * Providing correct {@param sourceURL} of downloaded bundle is required for JS stacktraces to
   * work correctly and allows for source maps to correctly symbolize those.
   */
  public static JSBundleLoader createCachedBundleFromNetworkLoader(
      final String sourceURL,
      final String cachedFileLocation) {
    return new JSBundleLoader() {
      @Override
      public void loadScript(ReactBridge bridge) {
        bridge.loadScriptFromFile(cachedFileLocation, sourceURL);
      }

      @Override
      public String getSourceUrl() {
        return sourceURL;
      }
    };
  }

  /**
   * This loader is used when proxy debugging is enabled. In that case there is no point in fetching
   * the bundle from device as remote executor will have to do it anyway.
   *
   * @param proxySourceURL the URL to load the JS bundle from in the JavaScript proxy
   * @param realSourceURL the URL to report as the source URL, e.g. for asset loading
   */
  public static JSBundleLoader createRemoteDebuggerBundleLoader(
      final String proxySourceURL,
      final String realSourceURL) {
    return new JSBundleLoader() {
      @Override
      public void loadScript(ReactBridge bridge) {
        bridge.loadScriptFromFile(null, proxySourceURL);
      }

      @Override
      public String getSourceUrl() {
        return realSourceURL;
      }
    };
  }

  public abstract void loadScript(ReactBridge bridge);
  public abstract String getSourceUrl();
}