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priyeshmashelkarjzheaux
priyeshmashelkar
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BAEL-2814 Added files for article (eugenp#6968)
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‎persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/projections/Product.java‎

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package com.baeldung.jpa.projections;
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import java.math.BigDecimal;
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import javax.persistence.Entity;
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import javax.persistence.GeneratedValue;
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import javax.persistence.GenerationType;
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import javax.persistence.Id;
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@Entity
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public class Product {
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@Id
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private long id;
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private String name;
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private String description;
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private String category;
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private BigDecimal unitPrice;
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public long getId() {
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return id;
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}
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public void setId(long id) {
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this.id = id;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getDescription() {
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return description;
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}
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public void setDescription(String description) {
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this.description = description;
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}
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public String getCategory() {
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return category;
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}
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public void setCategory(String category) {
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this.category = category;
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}
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public BigDecimal getUnitPrice() {
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return unitPrice;
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}
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public void setUnitPrice(BigDecimal unitPrice) {
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this.unitPrice = unitPrice;
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}
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}

‎persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/projections/ProductRepository.java‎

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package com.baeldung.jpa.projections;
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import java.util.List;
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import javax.persistence.EntityManager;
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import javax.persistence.EntityManagerFactory;
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import javax.persistence.Persistence;
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import javax.persistence.Query;
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import javax.persistence.Tuple;
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import javax.persistence.criteria.CriteriaBuilder;
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import javax.persistence.criteria.CriteriaQuery;
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import javax.persistence.criteria.Root;
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public class ProductRepository {
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private EntityManager entityManager;
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public ProductRepository() {
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EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa-projections");
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entityManager = factory.createEntityManager();
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}
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@SuppressWarnings("unchecked")
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public List<Object> findAllNamesUsingJPQL() {
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Query query = entityManager.createQuery("select name from Product");
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List<Object> resultList = query.getResultList();
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return resultList;
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}
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@SuppressWarnings("unchecked")
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public List<Object> findAllIdsUsingJPQL() {
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Query query = entityManager.createQuery("select id from Product");
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List<Object> resultList = query.getResultList();
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return resultList;
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}
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public List<String> findAllNamesUsingCriteriaBuilder() {
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CriteriaBuilder builder = entityManager.getCriteriaBuilder();
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CriteriaQuery<String> query = builder.createQuery(String.class);
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Root<Product> product = query.from(Product.class);
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query.select(product.get("name"));
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List<String> resultList = entityManager.createQuery(query).getResultList();
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return resultList;
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}
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@SuppressWarnings("unchecked")
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public List<Object[]> findAllIdAndNamesUsingJPQL() {
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Query query = entityManager.createQuery("select id, name from Product");
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List<Object[]> resultList = query.getResultList();
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return resultList;
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}
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public List<Object[]> findAllIdAndNamesUsingCriteriaBuilderArray() {
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CriteriaBuilder builder = entityManager.getCriteriaBuilder();
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CriteriaQuery<Object[]> query = builder.createQuery(Object[].class);
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Root<Product> product = query.from(Product.class);
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query.select(builder.array(product.get("id"), product.get("name")));
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List<Object[]> resultList = entityManager.createQuery(query).getResultList();
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return resultList;
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}
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public List<Object[]> findAllIdNameUnitPriceUsingCriteriaQueryMultiselect() {
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CriteriaBuilder builder = entityManager.getCriteriaBuilder();
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CriteriaQuery<Object[]> query = builder.createQuery(Object[].class);
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Root<Product> product = query.from(Product.class);
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query.multiselect(product.get("id"), product.get("name"), product.get("unitPrice"));
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List<Object[]> resultList = entityManager.createQuery(query).getResultList();
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return resultList;
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}
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public List<Tuple> findAllIdAndNamesUsingCriteriaBuilderTuple() {
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CriteriaBuilder builder = entityManager.getCriteriaBuilder();
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CriteriaQuery<Tuple> query = builder.createQuery(Tuple.class);
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Root<Product> product = query.from(Product.class);
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query.select(builder.tuple(product.get("id"), product.get("name")));
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List<Tuple> resultList = entityManager.createQuery(query).getResultList();
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return resultList;
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}
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public List<Object[]> findCountByCategoryUsingJPQL() {
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Query query = entityManager.createQuery("select p.category, count(p) from Product p group by p.category");
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return query.getResultList();
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}
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public List<Object[]> findCountByCategoryUsingCriteriaBuilder() {
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CriteriaBuilder builder = entityManager.getCriteriaBuilder();
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CriteriaQuery<Object[]> query = builder.createQuery(Object[].class);
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Root<Product> product = query.from(Product.class);
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query.multiselect(product.get("category"), builder.count(product));
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query.groupBy(product.get("category"));
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List<Object[]> resultList = entityManager.createQuery(query).getResultList();
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return resultList;
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}
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}

‎persistence-modules/java-jpa/src/main/resources/META-INF/persistence.xml‎

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<property name="hibernate.temp.use_jdbc_metadata_defaults" value="false" />
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</properties>
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</persistence-unit>
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<persistence-unit name="jpa-entity-definition">
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<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
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<class>com.baeldung.jpa.entity.Student</class>
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<property name="hibernate.temp.use_jdbc_metadata_defaults" value="false" />
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</properties>
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</persistence-unit>
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<persistence-unit name="jpa-projections">
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<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
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<class>com.baeldung.jpa.projections.Product</class>
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<exclude-unlisted-classes>true</exclude-unlisted-classes>
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<properties>
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<property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
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<property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test"/>
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<property name="javax.persistence.jdbc.user" value="sa"/>
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<property name="javax.persistence.jdbc.password" value=""/>
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<property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
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<property name="hibernate.hbm2ddl.auto" value="create-drop"/>
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<property name="show_sql" value="true"/>
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<property name="hibernate.temp.use_jdbc_metadata_defaults" value="false"/>
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<property name="javax.persistence.sql-load-script-source" value="products_jpa.sql"/>
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</properties>
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</persistence-unit>
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</persistence>

‎persistence-modules/java-jpa/src/main/resources/products_jpa.sql‎

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insert into product(id, name, description, category) values (1,'Product Name 1','This is Product 1', 'category1');
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insert into product(id, name, description, category) values (2,'Product Name 2','This is Product 2', 'category1');
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insert into product(id, name, description, category) values (3,'Product Name 3','This is Product 3', 'category2');
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insert into product(id, name, description, category) values (4,'Product Name 4','This is Product 4', 'category3');

‎persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/projections/HibernateProjectionsIntegrationTest.java‎

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package com.baeldung.jpa.projections;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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import java.util.List;
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import org.hibernate.Criteria;
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import org.hibernate.Session;
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import org.hibernate.SessionFactory;
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import org.hibernate.Transaction;
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import org.hibernate.cfg.AvailableSettings;
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import org.hibernate.cfg.Configuration;
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import org.hibernate.criterion.Order;
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import org.hibernate.criterion.Projections;
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import org.junit.After;
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import org.junit.Before;
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import org.junit.BeforeClass;
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import org.junit.Test;
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public class HibernateProjectionsIntegrationTest {
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private static Session session;
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private static SessionFactory sessionFactory;
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private Transaction transaction;
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@BeforeClass
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public static void init() {
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Configuration configuration = getConfiguration();
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configuration.addAnnotatedClass(Product.class);
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sessionFactory = configuration.buildSessionFactory();
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}
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@Before
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public void before() {
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session = sessionFactory.getCurrentSession();
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transaction = session.beginTransaction();
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}
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@After
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public void after() {
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if(transaction.isActive()) {
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transaction.rollback();
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}
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}
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private static Configuration getConfiguration() {
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Configuration cfg = new Configuration();
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cfg.setProperty(AvailableSettings.DIALECT,
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"org.hibernate.dialect.H2Dialect");
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cfg.setProperty(AvailableSettings.HBM2DDL_AUTO, "none");
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cfg.setProperty(AvailableSettings.DRIVER, "org.h2.Driver");
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cfg.setProperty(AvailableSettings.URL,
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"jdbc:h2:mem:myexceptiondb2;DB_CLOSE_DELAY=-1;;INIT=RUNSCRIPT FROM 'src/test/resources/products.sql'");
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cfg.setProperty(AvailableSettings.USER, "sa");
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cfg.setProperty(AvailableSettings.PASS, "");
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cfg.setProperty(AvailableSettings.CURRENT_SESSION_CONTEXT_CLASS, "thread");
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return cfg;
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}
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@SuppressWarnings("deprecation")
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@Test
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public void givenProductData_whenIdAndNameProjectionUsingCriteria_thenListOfObjectArrayReturned() {
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Criteria criteria = session.createCriteria(Product.class);
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criteria = criteria.setProjection(Projections.projectionList()
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.add(Projections.id())
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.add(Projections.property("name")));
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List<Object[]> resultList = criteria.list();
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assertNotNull(resultList);
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assertEquals(4, resultList.size());
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assertEquals(1L, resultList.get(0)[0]);
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assertEquals("Product Name 1", resultList.get(0)[1]);
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assertEquals(2L, resultList.get(1)[0]);
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assertEquals("Product Name 2", resultList.get(1)[1]);
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assertEquals(3L, resultList.get(2)[0]);
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assertEquals("Product Name 3", resultList.get(2)[1]);
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assertEquals(4L, resultList.get(3)[0]);
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assertEquals("Product Name 4", resultList.get(3)[1]);
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}
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@Test
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public void givenProductData_whenNameProjectionUsingCriteria_thenListOfStringReturned() {
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Criteria criteria = session.createCriteria(Product.class);
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criteria = criteria.setProjection(Projections.property("name"));
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List resultList = criteria.list();
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assertNotNull(resultList);
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assertEquals(4, resultList.size());
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assertEquals("Product Name 1", resultList.get(0));
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assertEquals("Product Name 2", resultList.get(1));
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assertEquals("Product Name 3", resultList.get(2));
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assertEquals("Product Name 4", resultList.get(3));
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}
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@Test
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public void givenProductData_whenCountByCategoryUsingCriteria_thenOK() {
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Criteria criteria = session.createCriteria(Product.class);
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criteria = criteria.setProjection(Projections.projectionList()
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.add(Projections.groupProperty("category"))
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.add(Projections.rowCount()));
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List<Object[]> resultList = criteria.list();
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assertNotNull(resultList);
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assertEquals(3, resultList.size());
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assertEquals("category1", resultList.get(0)[0]);
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assertEquals(2L, resultList.get(0)[1]);
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assertEquals("category2", resultList.get(1)[0]);
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assertEquals(1L, resultList.get(1)[1]);
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assertEquals("category3", resultList.get(2)[0]);
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assertEquals(1L, resultList.get(2)[1]);
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}
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@Test
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public void givenProductData_whenCountByCategoryWithAliasUsingCriteria_thenOK() {
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Criteria criteria = session.createCriteria(Product.class);
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criteria = criteria.setProjection(Projections.projectionList()
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.add(Projections.groupProperty("category"))
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.add(Projections.alias(Projections.rowCount(), "count")));
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criteria.addOrder(Order.asc("count"));
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List<Object[]> resultList = criteria.list();
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assertNotNull(resultList);
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assertEquals(3, resultList.size());
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assertEquals("category2", resultList.get(0)[0]);
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assertEquals(1L, resultList.get(0)[1]);
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assertEquals("category3", resultList.get(1)[0]);
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assertEquals(1L, resultList.get(1)[1]);
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assertEquals("category1", resultList.get(2)[0]);
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assertEquals(2L, resultList.get(2)[1]);
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}
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}

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