From 84314e279e2bc3bb9e87f7bcd5b186545083f3bd Mon Sep 17 00:00:00 2001
From: Mark Paluch <mpaluch@pivotal.io>
Date: Tue, 28 Jun 2016 14:55:26 +0200
Subject: [PATCH] DATAJPA-920 - Add support for exists projection in repository
 query derivation.

We now support exists projections in derived queries. Queries select the primary key using tuple queries limiting the result to the first row.

interface UserRepository extends Repository<User, Long> {
    boolean existsByFirstname(String firstname);
}

Original pull request: #176.
---
 .../jpa/repository/query/JpaQueryCreator.java | 30 ++++++++++--
 .../repository/query/JpaQueryExecution.java   | 14 ++++++
 .../repository/query/PartTreeJpaQuery.java    | 14 +++++-
 .../sample/EmbeddedIdExampleEmployee.java     | 13 ++++-
 .../sample/IdClassExampleDepartment.java      |  3 ++
 .../domain/sample/IdClassExampleEmployee.java | 16 ++++++-
 .../RepositoryWithCompositeKeyTests.java      | 47 ++++++++++++++++++-
 .../jpa/repository/UserRepositoryTests.java   | 12 +++++
 .../PartTreeJpaQueryIntegrationTests.java     | 31 ++++++++++++
 .../EmployeeRepositoryWithEmbeddedId.java     |  8 +++-
 .../sample/EmployeeRepositoryWithIdClass.java |  8 +++-
 .../jpa/repository/sample/UserRepository.java |  5 ++
 12 files changed, 192 insertions(+), 9 deletions(-)

diff --git a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
index 9f808a3ad..e5c98830d 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2015 the original author or authors.
+ * Copyright 2008-2016 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.
@@ -15,6 +15,7 @@
  */
 package org.springframework.data.jpa.repository.query;
 
+import static org.springframework.data.jpa.domain.AbstractPersistable_.*;
 import static org.springframework.data.jpa.repository.query.QueryUtils.*;
 import static org.springframework.data.repository.query.parser.Part.Type.*;
 
@@ -22,6 +23,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 
 import javax.persistence.criteria.CriteriaBuilder;
 import javax.persistence.criteria.CriteriaQuery;
@@ -31,6 +33,7 @@ import javax.persistence.criteria.Path;
 import javax.persistence.criteria.Predicate;
 import javax.persistence.criteria.Root;
 import javax.persistence.criteria.Selection;
+import javax.persistence.metamodel.SingularAttribute;
 
 import org.springframework.data.domain.Sort;
 import org.springframework.data.jpa.repository.query.ParameterMetadataProvider.ParameterMetadata;
@@ -46,6 +49,7 @@ import org.springframework.util.Assert;
  * Query creator to create a {@link CriteriaQuery} from a {@link PartTree}.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extends Object>, Predicate> {
 
@@ -54,6 +58,7 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 	private final CriteriaQuery<? extends Object> query;
 	private final ParameterMetadataProvider provider;
 	private final ReturnedType returnedType;
+	private final PartTree tree;
 
 	/**
 	 * Create a new {@link JpaQueryCreator}.
@@ -67,6 +72,7 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 			ParameterMetadataProvider provider) {
 
 		super(tree);
+		this.tree = tree;
 
 		CriteriaQuery<? extends Object> criteriaQuery = createCriteriaQuery(builder, type);
 
@@ -88,7 +94,7 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 
 		Class<?> typeToRead = type.getTypeToRead();
 
-		return typeToRead == null ? builder.createTupleQuery() : builder.createQuery(typeToRead);
+		return (typeToRead == null || tree.isExistsProjection()) ? builder.createTupleQuery() : builder.createQuery(typeToRead);
 	}
 
 	/**
@@ -163,6 +169,24 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 			}
 
 			query = query.multiselect(selections);
+		} else if (tree.isExistsProjection()) {
+
+			if (root.getModel().hasSingleIdAttribute()) {
+
+				SingularAttribute<?, ?> id = root.getModel().getId(root.getModel().getIdType().getJavaType());
+				query = query.multiselect(root.get((SingularAttribute) id).alias(id.getName()));
+			} else {
+
+				List<Selection<?>> selections = new ArrayList<Selection<?>>();
+
+				Set<SingularAttribute<?, ?>> idClassAttributes = (Set<SingularAttribute<?, ?>>) root.getModel().getIdClassAttributes();
+
+				for (SingularAttribute<?, ?> attribute : idClassAttributes) {
+					selections.add(root.get((SingularAttribute) attribute).alias(attribute.getName()));
+				}
+				selections.add(root.get((SingularAttribute) id).alias(id.getName()));
+				query = query.multiselect(selections);
+			}
 		} else {
 			query = query.select((Root) root);
 		}
@@ -173,7 +197,7 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 
 	/**
 	 * Creates a {@link Predicate} from the given {@link Part}.
-	 * 
+	 *
 	 * @param part
 	 * @param root
 	 * @param iterator
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
index 6a5833df3..6225934dd 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
@@ -276,6 +276,20 @@ public abstract class JpaQueryExecution {
 		}
 	}
 
+	/**
+	 * {@link Execution} performing an exists check on the query.
+	 *
+	 * @author Mark Paluch
+	 * @since 1.11
+	 */
+	static class ExistsExecution extends JpaQueryExecution {
+
+		@Override
+		protected Object doExecute(AbstractJpaQuery query, Object[] values) {
+			return !query.createQuery(values).getResultList().isEmpty();
+		}
+	}
+
 	/**
 	 * {@link Execution} executing a stored procedure.
 	 * 
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/PartTreeJpaQuery.java b/src/main/java/org/springframework/data/jpa/repository/query/PartTreeJpaQuery.java
index 501269d14..d780d0a9a 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/PartTreeJpaQuery.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/PartTreeJpaQuery.java
@@ -26,6 +26,7 @@ import javax.persistence.criteria.CriteriaQuery;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.jpa.provider.PersistenceProvider;
 import org.springframework.data.jpa.repository.query.JpaQueryExecution.DeleteExecution;
+import org.springframework.data.jpa.repository.query.JpaQueryExecution.ExistsExecution;
 import org.springframework.data.jpa.repository.query.ParameterMetadataProvider.ParameterMetadata;
 import org.springframework.data.repository.query.ParametersParameterAccessor;
 import org.springframework.data.repository.query.ResultProcessor;
@@ -94,7 +95,14 @@ public class PartTreeJpaQuery extends AbstractJpaQuery {
 	 */
 	@Override
 	protected JpaQueryExecution getExecution() {
-		return this.tree.isDelete() ? new DeleteExecution(em) : super.getExecution();
+
+		if(this.tree.isDelete()) {
+			return new DeleteExecution(em);
+		} else if(this.tree.isExistsProjection()) {
+			return new ExistsExecution();
+		}
+
+		return super.getExecution();
 	}
 
 	/**
@@ -168,6 +176,10 @@ public class PartTreeJpaQuery extends AbstractJpaQuery {
 				query.setMaxResults(tree.getMaxResults());
 			}
 
+			if(tree.isExistsProjection()) {
+				query.setMaxResults(1);
+			}
+
 			return query;
 		}
 
diff --git a/src/test/java/org/springframework/data/jpa/domain/sample/EmbeddedIdExampleEmployee.java b/src/test/java/org/springframework/data/jpa/domain/sample/EmbeddedIdExampleEmployee.java
index d56ce2aa0..b09fd5ead 100644
--- a/src/test/java/org/springframework/data/jpa/domain/sample/EmbeddedIdExampleEmployee.java
+++ b/src/test/java/org/springframework/data/jpa/domain/sample/EmbeddedIdExampleEmployee.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2104 the original author or authors.
+ * Copyright 2013-2016 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.
@@ -23,6 +23,7 @@ import javax.persistence.MapsId;
 
 /**
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 @Entity
 public class EmbeddedIdExampleEmployee {
@@ -33,6 +34,8 @@ public class EmbeddedIdExampleEmployee {
 	@ManyToOne(cascade = CascadeType.ALL)//
 	EmbeddedIdExampleDepartment department;
 
+	String name;
+
 	public EmbeddedIdExampleEmployeePK getEmployeePk() {
 		return employeePk;
 	}
@@ -48,4 +51,12 @@ public class EmbeddedIdExampleEmployee {
 	public void setDepartment(EmbeddedIdExampleDepartment department) {
 		this.department = department;
 	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
 }
diff --git a/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleDepartment.java b/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleDepartment.java
index c040b23fe..f7dba2b2d 100644
--- a/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleDepartment.java
+++ b/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleDepartment.java
@@ -18,6 +18,9 @@ package org.springframework.data.jpa.domain.sample;
 import javax.persistence.Entity;
 import javax.persistence.Id;
 
+/**
+ * @author Thomas Darimont
+ */
 @Entity
 public class IdClassExampleDepartment {
 
diff --git a/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleEmployee.java b/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleEmployee.java
index bf5be5e35..8ab1136d6 100644
--- a/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleEmployee.java
+++ b/src/test/java/org/springframework/data/jpa/domain/sample/IdClassExampleEmployee.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2016 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.
@@ -20,6 +20,10 @@ import javax.persistence.Id;
 import javax.persistence.IdClass;
 import javax.persistence.ManyToOne;
 
+/**
+ * @author Thomas Darimont
+ * @author Mark Paluch
+ */
 @IdClass(IdClassExampleEmployeePK.class)
 @Entity
 public class IdClassExampleEmployee {
@@ -27,6 +31,8 @@ public class IdClassExampleEmployee {
 	@Id long empId;
 	@Id @ManyToOne IdClassExampleDepartment department;
 
+	String name;
+
 	public long getEmpId() {
 		return empId;
 	}
@@ -42,4 +48,12 @@ public class IdClassExampleEmployee {
 	public void setDepartment(IdClassExampleDepartment department) {
 		this.department = department;
 	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
 }
diff --git a/src/test/java/org/springframework/data/jpa/repository/RepositoryWithCompositeKeyTests.java b/src/test/java/org/springframework/data/jpa/repository/RepositoryWithCompositeKeyTests.java
index 3416f27ca..e70db179b 100644
--- a/src/test/java/org/springframework/data/jpa/repository/RepositoryWithCompositeKeyTests.java
+++ b/src/test/java/org/springframework/data/jpa/repository/RepositoryWithCompositeKeyTests.java
@@ -46,7 +46,7 @@ import org.springframework.transaction.annotation.Transactional;
 
 /**
  * Tests some usage variants of composite keys with spring data jpa.
- * 
+ *
  * @author Thomas Darimont
  * @author Mark Paluch
  */
@@ -303,4 +303,49 @@ public class RepositoryWithCompositeKeyTests {
 
 		assertThat(result, hasSize(2));
 	}
+
+	/**
+	 * @see DATAJPA-920
+	 */
+	@Test
+	public void shouldExecuteExistsQueryForEntitiesWithEmbeddedId() {
+
+		EmbeddedIdExampleDepartment dep1 = new EmbeddedIdExampleDepartment();
+		dep1.setDepartmentId(1L);
+		dep1.setName("Dep1");
+
+		EmbeddedIdExampleEmployeePK key = new EmbeddedIdExampleEmployeePK();
+		key.setDepartmentId(1L);
+		key.setEmployeeId(1L);
+
+		EmbeddedIdExampleEmployee emp = new EmbeddedIdExampleEmployee();
+		emp.setDepartment(dep1);
+		emp.setEmployeePk(key);
+		emp.setName("White");
+
+		employeeRepositoryWithEmbeddedId.save(emp);
+
+		assertThat(employeeRepositoryWithEmbeddedId.existsByName(emp.getName()), is(true));
+	}
+
+	/**
+	 * @see DATAJPA-920
+	 */
+	@Test
+	public void shouldExecuteExistsQueryForEntitiesWithCompoundIdClassKeys() {
+
+		IdClassExampleDepartment dep2 = new IdClassExampleDepartment();
+		dep2.setDepartmentId(2L);
+		dep2.setName("Dep2");
+
+		IdClassExampleEmployee emp1 = new IdClassExampleEmployee();
+		emp1.setEmpId(3L);
+		emp1.setDepartment(dep2);
+		emp1.setName("White");
+
+		employeeRepositoryWithIdClass.save(emp1);
+
+		assertThat(employeeRepositoryWithIdClass.existsByName(emp1.getName()), is(true));
+		assertThat(employeeRepositoryWithIdClass.existsByName("Walter"), is(false));
+	}
 }
diff --git a/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java b/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java
index da24758bd..3a2ee4253 100644
--- a/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java
+++ b/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java
@@ -1096,6 +1096,18 @@ public class UserRepositoryTests {
 		assertThat(repository.countUsersByFirstname("Dave"), is(1));
 	}
 
+	/**
+	 * @see DATAJPA-231
+	 */
+	@Test
+	public void executesDerivedExistsQuery() {
+
+		flushTestUsers();
+
+		assertThat(repository.existsByLastname("Matthews"), is(true));
+		assertThat(repository.existsByLastname("Hans Peter"), is(false));
+	}
+
 	/**
 	 * @see DATAJPA-332
 	 */
diff --git a/src/test/java/org/springframework/data/jpa/repository/query/PartTreeJpaQueryIntegrationTests.java b/src/test/java/org/springframework/data/jpa/repository/query/PartTreeJpaQueryIntegrationTests.java
index 0ea336ef3..ebb09dae6 100644
--- a/src/test/java/org/springframework/data/jpa/repository/query/PartTreeJpaQueryIntegrationTests.java
+++ b/src/test/java/org/springframework/data/jpa/repository/query/PartTreeJpaQueryIntegrationTests.java
@@ -56,6 +56,7 @@ import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
  * Integration tests for {@link PartTreeJpaQuery}.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration("classpath:infrastructure.xml")
@@ -120,6 +121,34 @@ public class PartTreeJpaQueryIntegrationTests {
 		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY)), endsWith("firstname is null"));
 	}
 
+	/**
+	 * @see DATAJPA-920
+	 */
+	@Test
+	public void shouldLimitExistsProjectionQueries() throws Exception {
+
+		JpaQueryMethod queryMethod = getQueryMethod("existsByFirstname", String.class);
+		PartTreeJpaQuery jpaQuery = new PartTreeJpaQuery(queryMethod, entityManager, provider);
+
+		Query query = jpaQuery.createQuery(new Object[]{"Matthews"});
+
+		assertThat(query.getMaxResults(), is(1));
+	}
+
+	/**
+	 * @see DATAJPA-920
+	 */
+	@Test
+	public void shouldSelectAliasedIdForExistsProjectionQueries() throws Exception {
+
+		JpaQueryMethod queryMethod = getQueryMethod("existsByFirstname", String.class);
+		PartTreeJpaQuery jpaQuery = new PartTreeJpaQuery(queryMethod, entityManager, provider);
+
+		Query query = jpaQuery.createQuery(new Object[]{"Matthews"});
+
+		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY)), containsString(".id from User as"));
+	}
+
 	private void testIgnoreCase(String methodName, Object... values) throws Exception {
 
 		Class<?>[] parameterTypes = new Class[values.length];
@@ -173,6 +202,8 @@ public class PartTreeJpaQueryIntegrationTests {
 
 		User findByIdAllIgnoringCase(Integer id);
 
+		boolean existsByFirstname(String firstname);
+
 		List<User> findByCreatedAtAfter(@Temporal(TemporalType.TIMESTAMP) @Param("refDate") Date refDate);
 	}
 }
diff --git a/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithEmbeddedId.java b/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithEmbeddedId.java
index edf15484f..3454815fe 100644
--- a/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithEmbeddedId.java
+++ b/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithEmbeddedId.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2015 the original author or authors.
+ * Copyright 2013-2016 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.
@@ -30,6 +30,7 @@ import com.querydsl.core.types.Predicate;
  * Demonstrates the support for composite primary keys with {@code @EmbeddedId}.
  * 
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 @Lazy
 public interface EmployeeRepositoryWithEmbeddedId
@@ -37,4 +38,9 @@ public interface EmployeeRepositoryWithEmbeddedId
 		QueryDslPredicateExecutor<EmbeddedIdExampleEmployee> {
 
 	List<EmbeddedIdExampleEmployee> findAll(Predicate predicate, OrderSpecifier<?>... orders);
+
+	/**
+	 * @see DATAJPA-920
+	 */
+	boolean existsByName(String name);
 }
diff --git a/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithIdClass.java b/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithIdClass.java
index f5439053e..a5228e523 100644
--- a/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithIdClass.java
+++ b/src/test/java/org/springframework/data/jpa/repository/sample/EmployeeRepositoryWithIdClass.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2015 the original author or authors.
+ * Copyright 2013-2016 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.
@@ -30,10 +30,16 @@ import com.querydsl.core.types.Predicate;
  * Demonstrates the support for composite primary keys with {@code @IdClass}.
  * 
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 @Lazy
 public interface EmployeeRepositoryWithIdClass extends JpaRepository<IdClassExampleEmployee, IdClassExampleEmployeePK>,
 		QueryDslPredicateExecutor<IdClassExampleEmployee> {
 
 	List<IdClassExampleEmployee> findAll(Predicate predicate, OrderSpecifier<?>... orders);
+
+	/**
+	 * @see DATAJPA-920
+	 */
+	boolean existsByName(String name);
 }
diff --git a/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java b/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java
index b01d19ee1..e9f7c2c5f 100644
--- a/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java
+++ b/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java
@@ -282,6 +282,11 @@ public interface UserRepository
 	 */
 	int countUsersByFirstname(String firstname);
 
+	/**
+	 * @see DATAJPA-920
+	 */
+	boolean existsByLastname(String lastname);
+
 	/**
 	 * @see DATAJPA-391
 	 */