Use COALESCE for LIKE with wildcards.

To handle potential NULL values when LIKE is combined with wildcards, insert a COALESCE function.

See #3041

Author: gregturn

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

@@ -362,7 +362,7 @@ private static String potentiallyWrapWithWildcards(String replacement, String su
 				concatWrapper.append("'%',");
 			}
 
-			concatWrapper.append(replacement);
+			concatWrapper.append("COALESCE(" + replacement + ",'')");
 
 			if (substring.endsWith("%")) {
 				concatWrapper.append(",'%'");

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

@@ -99,7 +99,8 @@ void customQueryWithNullMatch() {
 
 		List<EmployeeWithName> Employees = repository.customQueryWithNullableParam(null);
 
-		assertThat(Employees).extracting(EmployeeWithName::getName).isEmpty();
+		assertThat(Employees).extracting(EmployeeWithName::getName).containsExactlyInAnyOrder("Frodo Baggins",
+				"Bilbo Baggins");
 	}
 
 	@Test // GH-2939
@@ -133,7 +134,8 @@ void customQueryWithNullMatchInNative() {
 
 		List<EmployeeWithName> Employees = repository.customQueryWithNullableParamInNative(null);
 
-		assertThat(Employees).extracting(EmployeeWithName::getName).isEmpty();
+		assertThat(Employees).extracting(EmployeeWithName::getName).containsExactlyInAnyOrder("Frodo Baggins",
+				"Bilbo Baggins");
 	}
 
 	@Test

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

@@ -64,8 +64,8 @@ void detectsPositionalLikeBindings() {
 				true);
 
 		assertThat(query.hasParameterBindings()).isTrue();
-		assertThat(query.getQueryString())
-				.isEqualTo("select u from User u where u.firstname like CONCAT('%',?1,'%') or u.lastname like CONCAT('%',?2)");
+		assertThat(query.getQueryString()).isEqualTo(
+				"select u from User u where u.firstname like CONCAT('%',COALESCE(?1,''),'%') or u.lastname like CONCAT('%',COALESCE(?2,''))");
 
 		List<ParameterBinding> bindings = query.getParameterBindings();
 		assertThat(bindings).hasSize(2);
@@ -87,7 +87,8 @@ void detectsNamedLikeBindings() {
 		StringQuery query = new StringQuery("select u from User u where u.firstname like %:firstname", true);
 
 		assertThat(query.hasParameterBindings()).isTrue();
-		assertThat(query.getQueryString()).isEqualTo("select u from User u where u.firstname like CONCAT('%',:firstname)");
+		assertThat(query.getQueryString())
+				.isEqualTo("select u from User u where u.firstname like CONCAT('%',COALESCE(:firstname,''))");
 
 		List<ParameterBinding> bindings = query.getParameterBindings();
 		assertThat(bindings).hasSize(1);
@@ -200,8 +201,8 @@ void removesLikeBindingsFromQueryIfQueryContainsSimpleBinding() {
 		assertNamedBinding(ParameterBinding.class, "word", bindings.get(1));
 
 		assertThat(query.getQueryString())
-				.isEqualTo("SELECT a FROM Article a WHERE a.overview LIKE CONCAT('%',:escapedWord,'%') ESCAPE '~'"
-						+ " OR a.content LIKE CONCAT('%',:escapedWord,'%') ESCAPE '~' OR a.title = :word ORDER BY a.articleId DESC");
+				.isEqualTo("SELECT a FROM Article a WHERE a.overview LIKE CONCAT('%',COALESCE(:escapedWord,''),'%') ESCAPE '~'"
+						+ " OR a.content LIKE CONCAT('%',COALESCE(:escapedWord,''),'%') ESCAPE '~' OR a.title = :word ORDER BY a.articleId DESC");
 	}
 
 	@Test // DATAJPA-483