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    /*
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.api.server.spi;

import com.google.api.server.spi.config.ApiConfigException;
import com.google.api.server.spi.config.ApiConfigLoader;
import com.google.api.server.spi.config.ApiConfigSource;
import com.google.api.server.spi.config.ApiConfigWriter;
import com.google.api.server.spi.config.annotationreader.ApiConfigAnnotationReader;
import com.google.api.server.spi.config.datastore.ApiConfigDatastoreReader;
import com.google.api.server.spi.config.jsonwriter.JsonConfigWriter;
import com.google.api.server.spi.config.model.ApiConfig;
import com.google.api.server.spi.config.model.ApiKey;
import com.google.api.server.spi.config.model.ApiMethodConfig;
import com.google.api.server.spi.config.model.ApiSerializationConfig;
import com.google.api.server.spi.config.model.ApiSerializationConfig.SerializerConfig;
import com.google.api.server.spi.config.validation.ApiConfigValidator;
import com.google.api.server.spi.discovery.CachingDiscoveryProvider;
import com.google.api.server.spi.discovery.ProxyingDiscoveryProvider;
import com.google.api.server.spi.discovery.ProxyingDiscoveryService;
import com.google.api.server.spi.request.ParamReader;
import com.google.api.server.spi.response.BadRequestException;
import com.google.api.server.spi.response.InternalServerErrorException;
import com.google.api.server.spi.response.ResultWriter;
import com.google.api.server.spi.response.UnauthorizedException;
import com.google.appengine.api.oauth.OAuthRequestException;
import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.annotation.Nullable;

/**
 * System service that execute service methods.
 */
public class SystemService {
  private static final Logger logger = Logger.getLogger(SystemService.class.getName());

  public static final String MIME_JSON = "application/json; charset=UTF-8";

  public static final int DUPLICATE_SERVICE_REGISTER_COUNT = -1;

  private static final Predicate NON_INTERNAL_PREDICATE =
      new Predicate() {
        @Override
        public boolean apply(ApiConfig config) {
          return !ApiConfigLoader.INTERNAL_API_NAME.equals(config.getName());
        }
      };

  private static final Function ENDPOINT_NODE_TO_API_CONFIG =
      new Function() {
        @Override
        public ApiConfig apply(EndpointNode node) {
          return node.config;
        }
      };

  /**
   * Mapping from service class name to Objects. This object will map both the simple and full
   * name of classes to an instance of it, therefore there could be more than one object mapped
   * to a simple name (i.e. package.v1.Hello and package.v2.Hello both have simple name "Hello"
   */
  private final Map> servicesByName;
  private final ConcurrentMap endpoints;
  private final Map serviceApiVersions;
  private final Map serializationConfigs;
  private final Multimap initialConfigsByApi;

  private final ApiConfigLoader configLoader;
  private final ApiConfigValidator validator;
  private final ServiceContext serviceContext;
  private final ApiConfigWriter configWriter;
  private final boolean isIllegalArgumentBackendError;

  public static class EndpointNode {
    private final Object endpoint;
    private final ApiConfig config;
    private final Map methods;

    EndpointNode(Object endpoint, ApiConfig config) {
      this.endpoint = endpoint;
      this.config = config;
      this.methods = new HashMap();
    }

    public Object getEndpoint() {
      return endpoint;
    }

    public ApiConfig getConfig() {
      return config;
    }

    public boolean isExternalEndpoint() {
      return !ApiConfigLoader.INTERNAL_API_NAME.equals(config.getName());
    }

    public Map getMethods() {
      return methods;
    }
  }

  /**
   * Constructs a {@link SystemService} and registers the provided services.
   *
   * @param configLoader The loader used to read annotation from service classes
   * @param appName The application's id
   * @param services The service classes to be registered
   */
  public SystemService(ApiConfigLoader configLoader, ApiConfigValidator validator, String appName,
      ApiConfigWriter configWriter, Object[] services, boolean isIllegalArgumentBackendError,
      boolean enableBackendService) throws ApiConfigException {
    this(configLoader, validator, appName, configWriter, isIllegalArgumentBackendError,
        enableBackendService);
    for (Object service : services) {
      registerService(service);
    }
  }

  /**
   * Constructs a {@link SystemService} with no registered services.
   *
   * @param configLoader The loader used to read annotation from service classes
   * @param appName The application's id
   */
  public SystemService(ApiConfigLoader configLoader, ApiConfigValidator validator, String appName,
      ApiConfigWriter configWriter, boolean isIllegalArgumentBackendError,
      boolean enableBackendService) throws ApiConfigException {
    this.servicesByName = new HashMap>();
    this.endpoints = new ConcurrentHashMap();
    this.serviceApiVersions = new HashMap();
    this.serializationConfigs = new HashMap();
    this.initialConfigsByApi = ArrayListMultimap.create();
    this.configLoader = configLoader;
    this.validator = validator;
    this.serviceContext = ServiceContext.create(appName, ServiceContext.DEFAULT_API_NAME);
    this.configWriter = configWriter;
    this.isIllegalArgumentBackendError = isIllegalArgumentBackendError;
    if (enableBackendService) {
      registerInternalService(new BackendService(this));
    }
  }

  /**
   * Registers a service class.  Only public methods in this class and all its superclasses, except
   * Object, are registered.  Two methods are not allowed to have the same name.  Registering a
   * different service with an existing name is a no-op.
   *
   * @param serviceClass is the class to start parsing endpoints
   * @param service Service object
   * @return number of service methods added, -1 on duplicate insertion
   * @throws ApiConfigException
   */
  public int registerService(Class serviceClass, Object service) throws ApiConfigException {
    Preconditions.checkArgument(serviceClass.isInstance(service),
        "service is not an instance of " + serviceClass.getName());
    ApiConfig apiConfig = configLoader.loadConfiguration(serviceContext, serviceClass);
    return registerLoadedService(serviceClass, service, apiConfig, true);
  }

  public int registerService(Object service) throws ApiConfigException {
    Class serviceClass = getServiceClass(service);
    return registerService(serviceClass, service);
  }

  private int registerInternalService(Object service) throws ApiConfigException {
    Class serviceClass = getServiceClass(service);
    ApiConfig apiConfig = configLoader.loadInternalConfiguration(serviceContext, serviceClass);
    return registerLoadedService(serviceClass, service, apiConfig, false);
  }

  private int registerLoadedService(Class serviceClass, Object service, ApiConfig apiConfig,
      boolean doValidation)
      throws ApiConfigException {
    String fullName = serviceClass.getName();
    if (!servicesByName.containsKey(fullName)) {
      // TODO: The bit below uses two maps to store per-API serialization configurations.
      // The first map maps service names to an api-version key, and the second map maps the key to
      // a serialization config. This is currently required because the API information is not kept
      // outside of this method, but it would be nice to find a better way to clean this up.
      String api = apiConfig.getName() + "-" + apiConfig.getVersion();
      if (doValidation) {
        validator.validate(Iterables.concat(initialConfigsByApi.get(api),
            Collections.singleton(apiConfig)));
      }
      initialConfigsByApi.put(api, apiConfig);

      ApiSerializationConfig serializationConfig = serializationConfigs.get(api);
      if (serializationConfig == null) {
        serializationConfig = new ApiSerializationConfig();
      }
      for (SerializerConfig rule : apiConfig.getSerializationConfig().getSerializerConfigs()) {
        serializationConfig.addSerializationConfig(rule.getSerializer());
      }
      serializationConfigs.put(api, serializationConfig);

      registerServiceFromName(service, serviceClass.getSimpleName(), api);
      registerServiceFromName(service, fullName, api);

      updateEndpointConfig(service, apiConfig, null);
      return apiConfig.getApiClassConfig().getMethods().size();
    }
    return DUPLICATE_SERVICE_REGISTER_COUNT;
  }

  public  EndpointNode updateEndpointConfig(T endpoint, ApiConfig newConfig,
      @Nullable EndpointNode oldNode) {
    EndpointNode newNode = new EndpointNode(endpoint, newConfig);
    for (EndpointMethod method : newConfig.getApiClassConfig().getMethods().keySet()) {
      newNode.methods.put(method.getMethod().getName(), method);
    }

    if (oldNode == null) {
      endpoints.putIfAbsent(endpoint, newNode);
    } else {
      endpoints.replace(endpoint, oldNode, newNode);
    }

    return newNode;
  }

  /**
   * Registers a service class.  Only public methods in this class and all its superclasses, except
   * Object, are registered.  Two methods are not allowed to have the same name.  Registering a
   * different service with an existing name is a no-op.
   *
   * @param service Service object
   * @param name Name at which the service is to be registered
   */
  void registerServiceFromName(final Object service, String name, String api) {
    List services = servicesByName.get(name);
    // If it doesn't exist, create
    if (services == null) {
      services = new ArrayList() {{ add(service); }};
      servicesByName.put(name, services);
    } else {
      // TODO: Throw an exception if a collision exists, when we no longer need to
      // support simple names.
      services.add(service);
    }
    serviceApiVersions.put(name, api);
  }

  /**
   * Finds a service object with the {@code serviceName} or {@code null} if not found.
   *
   * @param serviceName either a full class name or a simple name of a service object
   * @param methodName the method name of a service object
   * @throws ServiceException when more than one service is mapped to the same {@code name} or
   *         when the named service does not exist
   */
  public EndpointMethod resolveService(String serviceName, String methodName)
      throws ServiceException {
    return getEndpointNode(serviceName).methods.get(methodName);
  }

  /**
   * Resolves a service name and a method name to the {@link ApiMethodConfig} for the method
   * instance.
   */
  public ApiMethodConfig resolveAndUpdateServiceConfig(String serviceName, String methodName)
      throws ServiceException {
    EndpointNode node = getEndpointNode(serviceName);

    if (configLoader.isStaticConfig(node.config)) {
      return getMethodConfigFromNode(node, methodName);
    }

    ApiConfig newConfig;
    try {
      newConfig =
          configLoader.reloadConfiguration(serviceContext, getServiceClass(node.endpoint),
              node.config);
      validator.validate(newConfig);
    } catch (ApiConfigException e) {
      logger.log(Level.WARNING, "Could not load new endpoint config, defaulting to old.", e);
      return getMethodConfigFromNode(node, methodName);
    }

    if (!newConfig.equals(node.config)) {
      updateEndpointConfig(node.endpoint, newConfig, node);
    }

    return getMethodConfigFromNode(getEndpointNode(serviceName), methodName);
  }

  private ApiMethodConfig getMethodConfigFromNode(EndpointNode node, String methodName) {
    return node.config.getApiClassConfig().getMethods().get(node.methods.get(methodName));
  }

  /**
   * Gets the serialization configuration for the API corresponding to the named service.
   */
  public ApiSerializationConfig getSerializationConfig(String serviceName) {
    return serializationConfigs.get(serviceApiVersions.get(serviceName));
  }

  private EndpointNode getEndpointNode(String serviceName) throws ServiceException {
    Object service = findService(serviceName);
    EndpointNode node = endpoints.get(service);
    if (node == null) {
      throw new ServiceException(404, "service '" + serviceName + "' not found");
    } else {
      return node;
    }
  }

  /**
   * Finds a service object with the {@code name}
   *
   * @throws ServiceException when more than one service is mapped to the same {@code name} or
   *         when the named service does not exist
   */
  public Object findService(String name) throws ServiceException {
    List services = this.servicesByName.get(name);
    if (services == null || services.isEmpty()) {
      throw new ServiceException(404, "service '" + name + "' not found");
    } else if (services.size() > 1) {
      // Build exception for the ambiguous case.
      Class clazz = getServiceClass(services.get(0));
      Preconditions.checkState(name.equals(clazz.getSimpleName()),
          "Only requested simple class names should result in a collision.");
      StringBuilder builder = new StringBuilder(
          "Two or more Endpoint classes are mapped to the same service name (").append(name)
          .append("):");
      for (Object service : services) {
        builder.append(' ').append(getServiceClass(service).getName());
      }
      throw new ServiceException(500, builder.toString());
    } else {
      Object service = services.get(0);
      logger.log(Level.FINE, "{0} => {1}", new Object[]{name, services.get(0)});
      return service;
    }
  }

  /**
   * Finds a method object with the given {@code methodName} on the {@code service} object.
   *
   * @throws ServiceException if method does not exist
   */
  public Method findServiceMethod(Object service, String methodName) throws ServiceException {
    EndpointNode endpointNode = service == null ? null : endpoints.get(service);
    if (endpointNode != null) {
      EndpointMethod method = endpointNode.methods.get(methodName);
      if (method != null) {
        logger.log(Level.FINE, "serviceMethod={0}", method.getMethod());
        return method.getMethod();
      }
    }
    throw new ServiceException(404, "method '" + service + "." + methodName + "' not found");
  }

  /**
   * Invokes a {@code method} on a {@code service} given a {@code paramReader} to read parameters
   * and a {@code resultWriter} to write result.
   */
  public void invokeServiceMethod(Object service, Method method, ParamReader paramReader,
      ResultWriter resultWriter) throws IOException {

    Object[] params;
    try {
      params = paramReader.read();
      logger.log(Level.FINE, "params={0} (String)", Arrays.toString(params));
    } catch (BadRequestException e) {
      resultWriter.writeError(e);
      return;
    }

    Object response;
    try {
      response = method.invoke(service, params);
    } catch (IllegalArgumentException e) {
      logger.log(Level.SEVERE, "exception occurred while calling backend method", e);
      resultWriter.writeError(new BadRequestException(e));
      return;
    } catch (IllegalAccessException e) {
      logger.log(Level.SEVERE, "exception occurred while calling backend method", e);
      resultWriter.writeError(new BadRequestException(e));
      return;
    } catch (InvocationTargetException e) {
      Throwable cause = e.getCause();
      Level level = Level.INFO;

      if (cause instanceof ServiceException) {
        resultWriter.writeError((ServiceException) cause);
      } else if (cause instanceof IllegalArgumentException) {
        // If the backend call is to BackendService, this is an initialization error and needs to
        // be logged at a higher level than info. Otherwise, it could be thrown by the API. It is
        // transformed into a bad request response, so we don't need to log it at a high level.
        if (isIllegalArgumentBackendError
            || BackendService.class.equals(method.getDeclaringClass())) {
          level = Level.SEVERE;
        }
        resultWriter.writeError(
            isIllegalArgumentBackendError
                ? new InternalServerErrorException(cause) : new BadRequestException(cause));
      } else if (cause instanceof OAuthRequestException) {
        resultWriter.writeError(new UnauthorizedException(cause));
      } else if (cause.getCause() != null && cause.getCause() instanceof ServiceException) {
        cause = cause.getCause();
        resultWriter.writeError((ServiceException) cause);
      } else {
        level = Level.SEVERE;
        resultWriter.writeError(new InternalServerErrorException(cause));
      }
      logger.log(level, "exception occurred while calling backend method",
          cause);
      return;
    }

    resultWriter.write(response);
  }

  /**
   * Generates wire-format configuration for all loaded APIs.
   * @return A map from {@link ApiKey}s to wire-formatted configuration strings.
   */
  public Map getApiConfigs() throws ApiConfigException {
    return configWriter.writeConfig(
        FluentIterable.from(endpoints.values())
            .transform(ENDPOINT_NODE_TO_API_CONFIG)
            .filter(NON_INTERNAL_PREDICATE));
  }

  public ImmutableList getEndpoints() {
    return ImmutableList.copyOf(endpoints.values());
  }

  @SuppressWarnings("unchecked")
  private static  Class getServiceClass(T service) {
    Class clazz = service.getClass();
    Enhancers[] enhancers = Enhancers.values();
    for (int i = 0; i < enhancers.length; ++i) {
      if (enhancers[i].matches(clazz)) {
        clazz = clazz.getSuperclass();
        i = 0;
      }
    }
    return (Class) clazz;
  }

  private enum Enhancers {
    GUICE("$$EnhancerByGuice$$"),
    NONE(null);

    private final String enhancerSubstring;

    Enhancers(String enhancerSubstring) {
      this.enhancerSubstring = enhancerSubstring;
    }

    public boolean matches(Class clazz) {
      return enhancerSubstring != null && clazz.getSimpleName().contains(enhancerSubstring);
    }
  }

  public static Builder builder() {
    return new Builder();
  }

  /**
   * A {@link SystemService} builder which encapsulates common logic for building its dependencies.
   */
  public static class Builder {
    private ApiConfigLoader configLoader;
    private ApiConfigValidator configValidator;
    private String appName;
    private ApiConfigWriter configWriter;
    private boolean isIllegalArgumentBackendError;
    private boolean enableBackendService;
    private boolean enableDiscoveryService;
    private Map, Object> services = Maps.newLinkedHashMap();

    public Builder withDefaults(ClassLoader classLoader) throws ClassNotFoundException {
      setStandardConfigLoader(classLoader, true);
      setConfigValidator(new ApiConfigValidator());
      setAppName(new BackendProperties().getApplicationId());
      setConfigWriter(new JsonConfigWriter(classLoader, configValidator));
      isIllegalArgumentBackendError = false;
      enableBackendService = true;
      enableDiscoveryService = false;
      return this;
    }

    public Builder setStandardConfigLoader(ClassLoader classLoader, boolean enableDatastoreReader)
        throws ClassNotFoundException {
      TypeLoader typeLoader = new TypeLoader(classLoader);
      ApiConfigAnnotationReader annotationReader =
          new ApiConfigAnnotationReader(typeLoader.getAnnotationTypes());

      if (EnvUtil.isRunningOnAppEngine() && enableDatastoreReader) {
        ApiConfigSource datastoreReader = new ApiConfigDatastoreReader();
        this.configLoader = new ApiConfigLoader(new ApiConfig.Factory(), typeLoader,
            annotationReader, datastoreReader);
      } else {
        this.configLoader = new ApiConfigLoader(new ApiConfig.Factory(), typeLoader,
            annotationReader);
      }
      return this;
    }

    public Builder setConfigValidator(ApiConfigValidator configValidator) {
      this.configValidator = configValidator;
      return this;
    }

    public Builder setAppName(String appName) {
      this.appName = appName;
      return this;
    }

    public Builder setConfigWriter(ApiConfigWriter configWriter) {
      this.configWriter = configWriter;
      return this;
    }

    public Builder setIllegalArgumentIsBackendError(boolean isIllegalArgumentBackendError) {
      this.isIllegalArgumentBackendError = isIllegalArgumentBackendError;
      return this;
    }

    public Builder setBackendServiceEnabled(boolean enableBackendService) {
      this.enableBackendService = enableBackendService;
      return this;
    }

    public Builder setDiscoveryServiceEnabled(boolean enableDiscoveryService) {
      this.enableDiscoveryService = enableDiscoveryService;
      return this;
    }

    public Builder addService(Class serviceClass, Object service) {
      this.services.put(serviceClass, service);
      return this;
    }

    public SystemService build() throws ApiConfigException {
      Preconditions.checkNotNull(configLoader, "configLoader");
      Preconditions.checkNotNull(configValidator, "configValidator");
      Preconditions.checkNotNull(configWriter, "configWriter");
      SystemService systemService = new SystemService(configLoader, configValidator, appName,
          configWriter, isIllegalArgumentBackendError, enableBackendService);
      for (Entry, Object> entry : services.entrySet()) {
        systemService.registerService(entry.getKey(), entry.getValue());
      }
      // Discovery must come last so it can initialize correctly.
      if (enableDiscoveryService) {
        ProxyingDiscoveryService discoveryService = new ProxyingDiscoveryService();
        systemService.registerService(discoveryService);
        discoveryService.initialize(new CachingDiscoveryProvider(
            new ProxyingDiscoveryProvider(getApiConfigs(systemService), configWriter)));
      }
      return systemService;
    }

    private ImmutableList getApiConfigs(SystemService systemService) {
      ApiConfig.Factory factory = new ApiConfig.Factory();
      ImmutableList.Builder builder =
          ImmutableList.builder();
      for (EndpointNode node : systemService.getEndpoints()) {
        if (node.isExternalEndpoint()) {
          builder.add(factory.copy(node.getConfig()));
        }
      }
      return builder.build();
    }
  }
}

    
    
    
    

    




    
    
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