DATACMNS-636 - Add 'exists' method to QueryDslPredicateExecutor which accepts a querydsl Predicate.

Introduced exists(Predicate) method to QueryDslPredicateExecutor which enables other SD Repository implementations to provide this functionality without users having to manually declare the method on their interfaces.

Author: Thomas Darimont

src/main/java/org/springframework/data/querydsl/QueryDslPredicateExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2014 the original author or authors.
+ * Copyright 2011-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -83,4 +83,12 @@ public interface QueryDslPredicateExecutor<T> {
  * @return the number of instances matching the {@link Predicate}.
  */
 long count(Predicate predicate);
+
+/**
+ * Checks whether the data store contains elements that match the given {@link Predicate}.
+ *
+ * @param predicate the {@link Predicate} to use for the existance check, can be {@literal null}.
+ * @return {@literal true} if the data store contains elements that match the given {@link Predicate}.
+ */
+boolean exists(Predicate predicate);
 }