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Refine DTO projection rewrite for JPA 4.0 implicit mapping #4151

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Refine DTO projection rewrite for JPA 4.0 implicit mapping #4151

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29aa8af
Refine DTO projection rewrite for JPA 4.0 implicit mapping
Jan 11, 2026
e5908b4
Feat: add author name
Jan 11, 2026
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16 changes: 15 additions & 1 deletion .../java/org/springframework/data/jpa/repository/query/DtoProjectionTransformerDelegate.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@
* </ul>
*
* @author Mark Paluch
* @author HeeHoon Hong
* @since 3.5
*/
class DtoProjectionTransformerDelegate {
Expand All @@ -55,7 +56,20 @@ 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) {
Expand Down
9 changes: 5 additions & 4 deletions ...a/org/springframework/data/jpa/repository/query/AbstractDtoQueryTransformerUnitTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@
* Support class for unit tests for {@link DtoProjectionTransformerDelegate}.
*
* @author Mark Paluch
* @author HeeHoon Hong
*/
abstract class AbstractDtoQueryTransformerUnitTests<P extends JpaQueryEnhancer<? extends QueryInformation>> {

Expand All @@ -56,7 +57,7 @@ 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
Expand Down Expand Up @@ -99,7 +100,7 @@ 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
Expand All @@ -110,7 +111,7 @@ 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
Expand All @@ -122,7 +123,7 @@ 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) {
Expand Down