Add projection example using PredicateSpecification.

Closes #706

Author: mp911de

jpa/example/src/main/java/example/springdata/jpa/projections/CustomerRepository.java

@@ -1,11 +1,11 @@
 /*
- * Copyright 2015-2021 the original author or authors.
+ * Copyright 2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
- *      https://www.apache.org/licenses/LICENSE-2.0
+ *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -21,13 +21,15 @@
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.CrudRepository;
 
 /**
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
-public interface CustomerRepository extends CrudRepository<Customer, Long> {
+public interface CustomerRepository extends CrudRepository<Customer, Long>, JpaSpecificationExecutor<Customer> {
 
 	/**
 	 * Uses a projection interface to indicate the fields to be returned. As the projection doesn't use any dynamic

jpa/example/src/test/java/example/springdata/jpa/projections/CustomerRepositoryIntegrationTest.java

@@ -1,11 +1,11 @@
 /*
- * Copyright 2015-2021 the original author or authors.
+ * Copyright 2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
- *      https://www.apache.org/licenses/LICENSE-2.0
+ *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -37,8 +37,8 @@
  *
  * @author Oliver Gierke
  * @author Divya Srivastava
+ * @author Mark Paluch
  */
-
 @SpringBootTest
 @Transactional
 class CustomerRepositoryIntegrationTest {
@@ -136,4 +136,14 @@ void supportsProjectionInCombinationWithPagination() {
 	void appliesProjectionToOptional() {
 		assertThat(customers.findOptionalProjectionByLastname("Beauford")).isPresent();
 	}
+
+	@Test
+	void projectsWithSpecification() {
+
+		var result = customers.findBy((query, cb) -> cb.equal(query.get("firstname"), "Dave"),
+				it -> it.as(CustomerDto.class).all());
+
+		assertThat(result).hasSize(1);
+		assertThat(result).extracting(CustomerDto::firstname).containsOnly("Dave");
+	}
 }