Avoid DTO Constructor Expression rewriting for selection of nested properties.

We back off from rewriting String-based queries to use DTO Constructor expressions if the query selects a property that is assignable to the return type.

Closes #3862

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

@@ -161,7 +161,7 @@ abstract class AbstractStringBasedJpaQuery extends AbstractJpaQuery {
 		Class<?> returnedJavaType = processor.getReturnedType().getReturnedType();
 
 		if (query.isDefaultProjection() || !returnedType.isProjecting() || returnedJavaType.isInterface()
-				|| query.isNativeQuery()) {
+				|| query.isNative()) {
 			return returnedType;
 		}
 
@@ -178,23 +178,23 @@ abstract class AbstractStringBasedJpaQuery extends AbstractJpaQuery {
 			return new NonProjectingReturnedType(returnedType);
 		}
 
-		String alias = query.getAlias();
-		String projection = query.getProjection();
+		String projectionToUse = query.<@Nullable String> doWithEnhancer(queryEnhancer -> {
 
-		// we can handle single-column and no function projections here only
-		if (StringUtils.hasText(projection) && (projection.indexOf(',') != -1 || projection.indexOf('(') != -1)) {
-			return returnedType;
-		}
+			String alias = queryEnhancer.detectAlias();
+			String projection = queryEnhancer.getProjection();
 
-		if (StringUtils.hasText(alias) && StringUtils.hasText(projection)) {
-			alias = alias.trim();
-			projection = projection.trim();
-			if (projection.startsWith(alias + ".")) {
-				projection = projection.substring(alias.length() + 1);
+			// we can handle single-column and no function projections here only
+			if (StringUtils.hasText(projection) && (projection.indexOf(',') != -1 || projection.indexOf('(') != -1)) {
+				return null;
 			}
-		}
 
-		if (StringUtils.hasText(projection)) {
+			if (StringUtils.hasText(alias) && StringUtils.hasText(projection)) {
+				alias = alias.trim();
+				projection = projection.trim();
+				if (projection.startsWith(alias + ".")) {
+					projection = projection.substring(alias.length() + 1);
+				}
+			}
 
 			int space = projection.indexOf(' ');
 
@@ -202,10 +202,15 @@ abstract class AbstractStringBasedJpaQuery extends AbstractJpaQuery {
 				projection = projection.substring(0, space);
 			}
 
+			return projection;
+		});
+
+		if (StringUtils.hasText(projectionToUse)) {
+
 			Class<?> propertyType;
 
 			try {
-				PropertyPath from = PropertyPath.from(projection, getQueryMethod().getEntityInformation().getJavaType());
+				PropertyPath from = PropertyPath.from(projectionToUse, getQueryMethod().getEntityInformation().getJavaType());
 				propertyType = from.getLeafType();
 			} catch (PropertyReferenceException ignored) {
 				propertyType = null;
@@ -223,7 +228,7 @@ abstract class AbstractStringBasedJpaQuery extends AbstractJpaQuery {
 		return returnedType;
 	}
 
-	String getSortedQueryString(Sort sort, ReturnedType returnedType) {
+	QueryProvider getSortedQuery(Sort sort, ReturnedType returnedType) {
 		return querySortRewriter.getSorted(query, sort, returnedType);
 	}
 

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

@@ -16,6 +16,7 @@
 package org.springframework.data.jpa.repository.query;
 
 import java.util.List;
+import java.util.function.Function;
 
 import org.jspecify.annotations.Nullable;
 
@@ -46,6 +47,11 @@ class DefaultEntityQuery implements EntityQuery, DeclaredQuery {
 		this.queryEnhancer = queryEnhancerFactory.create(query);
 	}
 
+	@Override
+	public <T> T doWithEnhancer(Function<QueryEnhancer, T> function) {
+		return function.apply(queryEnhancer);
+	}
+
 	@Override
 	public boolean isNative() {
 		return query.isNative();

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

@@ -17,6 +17,7 @@ package org.springframework.data.jpa.repository.query;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Function;
 
 import org.jspecify.annotations.Nullable;
 
@@ -33,6 +34,8 @@ enum EmptyIntrospectedQuery implements EntityQuery {
 
 	EmptyIntrospectedQuery() {}
 
+
+
 	@Override
 	public boolean hasParameterBindings() {
 		return false;
@@ -57,11 +60,21 @@ enum EmptyIntrospectedQuery implements EntityQuery {
 		return null;
 	}
 
+	@Override
+	public <T> T doWithEnhancer(Function<QueryEnhancer, T> function) {
+		return null;
+	}
+
 	@Override
 	public boolean hasConstructorExpression() {
 		return false;
 	}
 
+	@Override
+	public boolean isNative() {
+		return false;
+	}
+
 	@Override
 	public boolean isDefaultProjection() {
 		return false;

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

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.jpa.repository.query;
 
+import java.util.function.Function;
+
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -45,6 +47,15 @@ public interface EntityQuery extends ParametrizedQuery {
 		return new DefaultEntityQuery(preparsed, enhancerFactory);
 	}
 
+	/**
+	 * Apply a {@link Function} to the query enhancer used by this query.
+	 *
+	 * @param function the callback function.
+	 * @return
+	 * @param <T>
+	 */
+	<T extends @Nullable Object> T doWithEnhancer(Function<QueryEnhancer, T> function);
+
 	/**
 	 * Returns whether the query is using a constructor expression.
 	 *
@@ -52,6 +63,11 @@ public interface EntityQuery extends ParametrizedQuery {
 	 */
 	boolean hasConstructorExpression();
 
+	/**
+	 * @return whether the underlying query has at least one named parameter.
+	 */
+	boolean isNative();
+
 	/**
 	 * Returns whether the query uses the default projection, i.e. returns the main alias defined for the query.
 	 */

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

@@ -30,7 +30,7 @@ import java.util.List;
  * @see EntityQuery#create(DeclaredQuery, QueryEnhancerSelector)
  * @see TemplatedQuery#create(String, JpaQueryMethod, JpaQueryConfiguration)
  */
-interface ParametrizedQuery extends QueryProvider {
+public interface ParametrizedQuery extends QueryProvider {
 
 	/**
 	 * @return whether the underlying query has at least one parameter.