implement requested changes

issue spring-projects#3501

Author: dmfrey

spring-integration-graphql/src/main/java/org/springframework/integration/graphql/outbound/GraphQlMessageHandler.java

@@ -61,6 +61,7 @@ public GraphQlMessageHandler(final GraphQlService graphQlService) {
 	 * @param query the GraphQL query to use.
 	 */
 	public void setQuery(String query) {
+		Assert.hasText(query, "'query' must not be empty");
 		setQueryExpression(new LiteralExpression(query));
 	}
 
@@ -107,20 +108,23 @@ protected final void doInit() {
 
 	@Override
 	protected Object handleRequestMessage(Message<?> requestMessage) {
+		RequestInput requestInput = null;
 
 		if (requestMessage.getPayload() instanceof RequestInput) {
 
-			return this.graphQlService
-					.execute((RequestInput) requestMessage.getPayload());
+			requestInput = (RequestInput) requestMessage.getPayload();
 		}
 		else  {
 			Assert.notNull(this.queryExpression, "'queryExpression' must not be null");
 			String query = evaluateQueryExpression(requestMessage);
 			String operationName = evaluateOperationNameExpression(requestMessage);
 			Map<String, Object> variables = evaluateVariablesExpression(requestMessage);
-			return this.graphQlService
-					.execute(new RequestInput(query, operationName, variables));
+			requestInput = new RequestInput(query, operationName, variables);
 		}
+
+		return this.graphQlService
+				.execute(requestInput);
+
 	}
 
 	private String evaluateQueryExpression(Message<?> message) {

spring-integration-graphql/src/main/java/org/springframework/integration/graphql/outbound/package-info.java

@@ -1 +1,4 @@
+/**
+ * Provides classes for outbound channel adapters over GraphQL.
+ */
 package org.springframework.integration.graphql.outbound;

src/reference/asciidoc/graphql.adoc

@@ -6,18 +6,17 @@ Spring Integration provides support for GraphQL.
 You need to include this dependency into your project:
 
 ====
+[source, xml, subs="normal", role="primary"]
 .Maven
-[source, xml, subs="normal"]
 ----
 <dependency>
     <groupId>org.springframework.integration</groupId>
     <artifactId>spring-integration-graphql</artifactId>
     <version>{project-version}</version>
 </dependency>
 ----
-
+[source, groovy, subs="normal", role="secondary"]
 .Gradle
-[source, groovy, subs="normal"]
 ----
 compile "org.springframework.integration:spring-integration-graphql:{project-version}"
 ----