【GraphQL Java 源码解析】Execution

Spring boot 执行 GraphQL通过 AbstractGraphQLHttpServlet 执行的

GraphQLSchema schema = GraphQLSchema.newSchema()
                .query(queryType)
                .build();

        ExecutionInput executionInput = ExecutionInput.newExecutionInput().query("query { hero { name } }")
                .build();

        GraphQL graphQL = GraphQL.newGraphQL(schema)
                .build();


        ExecutionResult executionResult = graphQL.execute(executionInput);

        Object data = executionResult.getData();
        List<GraphQLError> errors = executionResult.getErrors();

1.  AbstractGraphQLHttpServlet doGet/doPost 标准的servlet

2. HttpRequestHandlerImpl.handle 构建 GraphQLInvocationInput

3. HttpRequestInvokerImpl.execute 

4.GraphQLInvoker.executeAsync 构建 GraphQL

5. GraphQL.executeAsync 构建Execution

6. Execution.execute 构建ExecutionStrategy 

7.ExecutionStrategy.execute 递归调用每个field，如果有子field，会递归调用，并返回每个field的调用结果。

 

for (String fieldName : fieldNames) {
           
            CompletableFuture<FieldValueInfo> future = resolveFieldWithInfo(executionContext, newParameters);
        }

7.1 构建 DataFetchingEnvironment，查找对应的DataFetcher，调用 dataFetcher的get获取每个field的值。

protected fetchField() {
        
        DataFetchingEnvironment environment = newDataFetchingEnvironment(executionContext)
                .source(parameters.getSource())
                .localContext(parameters.getLocalContext())
                .arguments(argumentValues)
                .fieldDefinition(fieldDef)
                .mergedField(parameters.getField())
                .fieldType(fieldType)
                .executionStepInfo(executionStepInfo)
                .parentType(parentType)
                .selectionSet(fieldCollector)
                .queryDirectives(queryDirectives)
                .build();

        DataFetcher<?> dataFetcher = codeRegistry.getDataFetcher(parentType, fieldDef);

       
            Object fetchedValueRaw = dataFetcher.get(environment);
         }

 7.3 完成一次调用，如果时普通的返回类型，则直接跳出，否则 进入 completeValueForObject，递归调用处理孩子的信息

completeValue()  {
       

        if (result == null) {
            fieldValue = completeValueForNull(parameters);
            return FieldValueInfo.newFieldValueInfo(NULL).fieldValue(fieldValue).build();
        } else if (isList(fieldType)) {
            return completeValueForList(executionContext, parameters, result);
        } else if (isScalar(fieldType)) {
            fieldValue = completeValueForScalar(executionContext, parameters, (GraphQLScalarType) fieldType, result);
            return FieldValueInfo.newFieldValueInfo(SCALAR).fieldValue(fieldValue).build();
        } else if (isEnum(fieldType)) {
            fieldValue = completeValueForEnum(executionContext, parameters, (GraphQLEnumType) fieldType, result);
            return FieldValueInfo.newFieldValueInfo(ENUM).fieldValue(fieldValue).build();
        }

        // when we are here, we have a complex type: Interface, Union or Object
        // and we must go deeper
        //
        GraphQLObjectType resolvedObjectType;
        try {
            resolvedObjectType = resolveType(executionContext, parameters, fieldType);
            fieldValue = completeValueForObject(executionContext, parameters, resolvedObjectType, result);
        } catch (UnresolvedTypeException ex) {
           
        }
        return FieldValueInfo.newFieldValueInfo(OBJECT).fieldValue(fieldValue).build();
    }

 7.4 completeValueForObject调用，构建一个新的ExecutionStrategyParameters参数链，并递归调用7.1的流程

 

protected  completeValueForObject() {
       
        ExecutionStrategyParameters newParameters = parameters.transform(builder ->
                builder.executionStepInfo(newExecutionStepInfo)
                        .fields(subFields)
                        .nonNullFieldValidator(nonNullableFieldValidator)
                        .source(result)
        );

        // Calling this from the executionContext to ensure we shift back from mutation strategy to the query strategy.

        return executionContext.getQueryStrategy().execute(executionContext, newParameters);
    }

7.5 构建 ExecutionResult 并返回最终的输出值。