Consistently type check analysis server request parameters.

pkg/analysis_server/lib/src/domain_server.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library domain.server;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
@@ skipping 74 matching lines @@
     }
     return null;
   }
 
   /**
    * Create a new context in which analysis can be performed. The context that
    * is created will persist until server.deleteContext is used to delete it.
    * Clients, therefore, are responsible for managing the lifetime of contexts.
    */
   Response createContext(Request request) {
-    String sdkDirectory = request.getRequiredParameter(SDK_DIRECTORY_PARAM);
-    Map<String, String> packageMap = request.getParameter(PACKAGE_MAP_PARAM);
+    String sdkDirectory = request.getRequiredParameter(SDK_DIRECTORY_PARAM).asString();
+    Map<String, String> packageMap = request.getParameter(PACKAGE_MAP_PARAM, {}).asStringMap();
 
-    String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM);
+    String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM).asString();
     if (server.contextMap.containsKey(contextId)) {
       return new Response.contextAlreadyExists(request);
     }
     AnalysisContext context = AnalysisEngine.instance.createAnalysisContext();
     // TODO(brianwilkerson) Use the information from the request to set the
     // source factory in the context.
     DirectoryBasedDartSdk sdk;
     try {
       sdk = new DirectoryBasedDartSdk(new JavaFile(sdkDirectory));
     } on Exception catch (e) {
@@ skipping 10 matching lines @@
 
     Response response = new Response(request.id);
     return response;
   }
 
   /**
    * Delete the context with the given id. Future attempts to use the context id
    * will result in an error being returned.
    */
   Response deleteContext(Request request) {
-    String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM);
+    String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM).asString();
 
     AnalysisContext removedContext = server.contextMap.remove(contextId);
     if (removedContext == null) {
       return new Response.contextDoesNotExist(request);
     }
     Response response = new Response(request.id);
     return response;
   }
 
   /**
    * Cleanly shutdown the analysis server.
    */
   Response shutdown(Request request) {
     server.running = false;
     Response response = new Response(request.id);
     return response;
   }
 
   /**
    * Return the version number of the analysis server.
    */
   Response version(Request request) {
     Response response = new Response(request.id);
     response.setResult(VERSION_RESULT, '0.0.1');
     return response;
   }
 }