Update Eclipselink grammar to support = & != for null comparison.

Eclipselink transforms = & and != in queries into IS and IS NOT.

Closes #3314
Original pull request: #3316

Author: christophstrobl

spring-data-jpa/src/main/antlr4/org/springframework/data/jpa/repository/query/Eql.g4

@@ -362,7 +362,7 @@ like_expression
     ;
 
 null_comparison_expression
-    : (single_valued_path_expression | input_parameter | nullif_expression) IS (NOT)? NULL
+    : (single_valued_path_expression | input_parameter | nullif_expression) ((IS (NOT)?) | (op=(EQUAL | NOT_EQUAL))) NULL
     ;
 
 empty_collection_comparison_expression

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/EqlQueryRenderer.java

@@ -1315,10 +1315,13 @@ public List<JpaQueryParsingToken> visitNull_comparison_expression(EqlParser.Null
 			tokens.addAll(visit(ctx.nullif_expression()));
 		}
 
-		tokens.add(new JpaQueryParsingToken(ctx.IS()));
-
-		if (ctx.NOT() != null) {
-			tokens.add(new JpaQueryParsingToken(ctx.NOT()));
+		if (ctx.op != null) {
+			tokens.add(new JpaQueryParsingToken(ctx.op.getText()));
+		} else {
+			tokens.add(new JpaQueryParsingToken(ctx.IS()));
+			if (ctx.NOT() != null) {
+				tokens.add(new JpaQueryParsingToken(ctx.NOT()));
+			}
 		}
 		tokens.add(new JpaQueryParsingToken(ctx.NULL()));
 

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/query/EqlComplianceTests.java

@@ -401,4 +401,17 @@ void coalesceFunctions() {
 		assertQuery("SELECT b FROM Bundle b WHERE coalesce(b.deleted, false) AND b.latestImport = true");
 		assertQuery("SELECT b FROM Bundle b WHERE NOT coalesce(b.deleted, false) AND b.latestImport = true");
 	}
+
+	@Test // GH-3314
+	void isNullAndIsNotNull() {
+
+		assertQuery("SELECT e FROM Employee e WHERE (e.active = null OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active = NULL OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active IS null OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active IS NULL OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active != null OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active != NULL OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active IS NOT null OR e.active = true)");
+		assertQuery("SELECT e FROM Employee e WHERE (e.active IS NOT NULL OR e.active = true)");
+	}
 }