Allow configuring execution strategy

Author: yrashk

src/main/java/graphql/servlet/EnhancedExecutionStrategyProvider.java

@@ -0,0 +1,25 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * 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
+ */
+package graphql.servlet;
+
+import graphql.annotations.EnhancedExecutionStrategy;
+import graphql.execution.ExecutionStrategy;
+
+public class EnhancedExecutionStrategyProvider implements ExecutionStrategyProvider {
+    @Override
+    public ExecutionStrategy getExecutionStrategy() {
+        return new EnhancedExecutionStrategy();
+    }
+}

src/main/java/graphql/servlet/ExecutionStrategyProvider.java

@@ -0,0 +1,21 @@
+/**
+ * Copyright 2016 Yurii Rashkovskii
+ *
+ * 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
+ */
+package graphql.servlet;
+
+import graphql.execution.ExecutionStrategy;
+
+public interface ExecutionStrategyProvider {
+    ExecutionStrategy getExecutionStrategy();
+}

src/main/java/graphql/servlet/GraphQLServlet.java

@@ -17,7 +17,6 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.io.CharStreams;
 import graphql.*;
-import graphql.annotations.EnhancedExecutionStrategy;
 import graphql.schema.GraphQLFieldDefinition;
 import graphql.schema.GraphQLObjectType;
 import graphql.schema.GraphQLSchema;
@@ -118,6 +117,7 @@ public String[] getMutations() {
     }
 
     private GraphQLContextBuilder contextBuilder = new DefaultGraphQLContextBuilder();
+    private ExecutionStrategyProvider executionStrategyProvider = new EnhancedExecutionStrategyProvider();
 
     @Reference
     public void setContextProvider(GraphQLContextBuilder contextBuilder) {
@@ -127,6 +127,14 @@ public void unsetContextProvider(GraphQLContextBuilder contextBuilder) {
         this.contextBuilder = new DefaultGraphQLContextBuilder();
     }
 
+    @Reference
+    public void setExecutionStrategyProvider(ExecutionStrategyProvider provider) {
+        executionStrategyProvider = provider;
+    }
+    public void unsetExecutionStrategyProvider(ExecutionStrategyProvider provider) {
+        executionStrategyProvider = new EnhancedExecutionStrategyProvider();
+    }
+
     protected GraphQLContext createContext(Optional<HttpServletRequest> req, Optional<HttpServletResponse> resp) {
         return contextBuilder.build(req, resp);
     }
@@ -180,7 +188,7 @@ public Void run() {
                 }
             });
         } else {
-            ExecutionResult result = new GraphQL(schema, new EnhancedExecutionStrategy()).execute(query, context, variables);
+            ExecutionResult result = new GraphQL(schema, executionStrategyProvider.getExecutionStrategy()).execute(query, context, variables);
             resp.setContentType("application/json");
             if (result.getErrors().isEmpty()) {
                 Map<String, Object> dict = new HashMap<>();