INT-1639 Externalize SpEL Evaluation Context

Allow modification of context property accessors and
functions.

Polishing

- Fix tests to ensure the EvaluationContextFactoryBean is
available when necessary.

Polishing - Use Utility for ALL EvaluationContexts

Add Test Showing Custom Function

See SpelTransformerIntegrationTests-context.xml

Polishing

Polishing -fix Remote Sync

Polishing - Emit WARN if No BeanFactory

Polishing - Do Not Override ConversionService

Kludge to Prevent Warning When No BeanFactory

Expressions for method invoking in the MessagingMethodInvokerHelper
don't need a BeanFactory - suppress the warning.

Polishing - PR Comments - Invert Boolean

spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/inbound/MongoDbMessageSource.java

@@ -168,13 +168,8 @@ public class MongoDbMessageSource extends IntegrationObjectSupport
 
 	@Override
 	protected void onInit() throws Exception {
-		if (this.getBeanFactory() != null){
-			this.evaluationContext =
+		this.evaluationContext =
 					ExpressionUtils.createStandardEvaluationContext(this.getBeanFactory());
-		}
-		else {
-			this.evaluationContext = ExpressionUtils.createStandardEvaluationContext();
-		}
 
 		if (this.mongoTemplate == null){
 			this.mongoTemplate = new MongoTemplate(this.mongoDbFactory, this.mongoConverter);

spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/outbound/MongoDbStoringMessageHandler.java

@@ -99,13 +99,8 @@ public class MongoDbStoringMessageHandler extends AbstractMessageHandler {
 
 	@Override
 	protected void onInit() throws Exception {
-		if (this.getBeanFactory() != null) {
-			this.evaluationContext =
+		this.evaluationContext =
 					ExpressionUtils.createStandardEvaluationContext(this.getBeanFactory());
-		}
-		else {
-			this.evaluationContext = ExpressionUtils.createStandardEvaluationContext();
-		}
 		if (this.mongoTemplate == null){
 			this.mongoTemplate = new MongoTemplate(this.mongoDbFactory, this.mongoConverter);
 		}