Refine DTO projection rewrite for JPA 4.0 implicit mapping

Author: heehoonhong

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

@@ -55,7 +55,20 @@ public boolean applyRewriting() {
 	}
 
 	public boolean canRewrite() {
-		return !selectItems.isEmpty() && applyRewriting();
+
+		if (selectItems.isEmpty() || !applyRewriting()) {
+			return false;
+		}
+
+		// Avoid rewriting if the selection list is already expanded and the target type is a record
+		// to leverage JPA 4.0 implicit DTO mapping.
+		boolean expansion = selectItems.size() == 1 && selectItems.get(0).size() == 1;
+
+		if (!expansion && returnedType.getReturnedType().isRecord()) {
+			return false;
+		}
+
+		return true;
 	}
 
 	public void appendSelectItem(QueryTokenStream selectItem) {

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

@@ -56,7 +56,7 @@ void shouldRewriteSelectionToConstructorExpression() {
 		QueryTokenStream visit = getTransformer(parser).visit(parser.getContext());
 
 		assertThat(QueryRenderer.TokenRenderer.render(visit)).isEqualTo(
-				"SELECT new org.springframework.data.jpa.repository.query.AbstractDtoQueryTransformerUnitTests$MyRecord(p.name) from Person p");
+				"SELECT p.name from Person p");
 	}
 
 	@Test // GH-3076
@@ -99,7 +99,7 @@ void shouldTranslatePropertySelectionToDto() {
 		QueryTokenStream visit = getTransformer(parser).visit(parser.getContext());
 
 		assertThat(QueryRenderer.TokenRenderer.render(visit)).isEqualTo(
-				"SELECT new org.springframework.data.jpa.repository.query.AbstractDtoQueryTransformerUnitTests$MyRecord(p.foo, p.bar, sum(p.age)) from Person p");
+				"SELECT p.foo, p.bar, sum(p.age) from Person p");
 	}
 
 	@Test // GH-3895
@@ -110,7 +110,7 @@ void shouldStripAliasesFromDtoProjection() {
 		QueryTokenStream visit = getTransformer(parser).visit(parser.getContext());
 
 		assertThat(QueryRenderer.TokenRenderer.render(visit)).isEqualTo(
-				"SELECT new org.springframework.data.jpa.repository.query.AbstractDtoQueryTransformerUnitTests$MyRecord(sum(p.age), p.foo, p.bar) from Person p");
+				"SELECT sum(p.age) As age, p.foo as foo, p.bar AS bar from Person p");
 	}
 
 	@Test // GH-3895
@@ -122,7 +122,7 @@ void shouldStripAliasesFromDtoProjectionWithSubquery() {
 		QueryTokenStream visit = getTransformer(parser).visit(parser.getContext());
 
 		assertThat(QueryRenderer.TokenRenderer.render(visit)).isEqualTo(
-				"SELECT new org.springframework.data.jpa.repository.query.AbstractDtoQueryTransformerUnitTests$MyRecord(p.foo, p.bar, cast(p.age as INTEGER), (SELECT b.foo FROM Bar AS b)) from Person p");
+				"SELECT p.foo as foo, p.bar AS bar, cast(p.age as INTEGER) As age, (SELECT b.foo FROM Bar AS b) from Person p");
 	}
 
 	private JpaQueryMethod getMethod(String name, Class<?>... parameterTypes) {