JPA pagination examples

Author: eugenp

spring-jpa/src/main/java/org/baeldung/persistence/service/FooService.java

@@ -1,5 +1,7 @@
 package org.baeldung.persistence.service;
 
+import java.util.List;
+
 import org.baeldung.persistence.dao.IFooDao;
 import org.baeldung.persistence.model.Foo;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -27,4 +29,8 @@ public Foo findOne(final long id) {
         return dao.findOne(id);
     }
 
+    public List<Foo> findAll() {
+        return dao.findAll();
+    }
+
 }

spring-jpa/src/test/java/org/baeldung/persistence/service/FooPaginationPersistenceIntegrationTest.java

@@ -0,0 +1,152 @@
+package org.baeldung.persistence.service;
+
+import static org.apache.commons.lang3.RandomStringUtils.randomAlphabetic;
+import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.lessThan;
+import static org.junit.Assert.assertThat;
+
+import java.util.List;
+
+import javax.persistence.EntityManager;
+import javax.persistence.PersistenceContext;
+import javax.persistence.Query;
+import javax.persistence.TypedQuery;
+import javax.persistence.criteria.CriteriaBuilder;
+import javax.persistence.criteria.CriteriaQuery;
+import javax.persistence.criteria.Root;
+
+import org.baeldung.config.PersistenceJPAConfig;
+import org.baeldung.persistence.model.Foo;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = { PersistenceJPAConfig.class }, loader = AnnotationConfigContextLoader.class)
+public class FooPaginationPersistenceIntegrationTest {
+
+    @PersistenceContext
+    private EntityManager entityManager;
+
+    @Autowired
+    private FooService fooService;
+
+    @Before
+    public final void before() {
+        final int minimalNumberOfEntities = 25;
+        if (fooService.findAll().size() <= minimalNumberOfEntities) {
+            for (int i = 0; i < minimalNumberOfEntities; i++) {
+                fooService.create(new Foo(randomAlphabetic(6)));
+            }
+        }
+    }
+
+    // tests
+
+    @Test
+    public final void whenContextIsBootstrapped_thenNoExceptions() {
+        //
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public final void givenEntitiesExist_whenRetrievingFirstPage_thenCorrect() {
+        final int pageSize = 10;
+
+        final Query query = entityManager.createQuery("From Foo");
+        configurePagination(query, 1, pageSize);
+
+        // When
+        final List<Foo> fooList = query.getResultList();
+
+        // Then
+        assertThat(fooList, hasSize(pageSize));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public final void givenEntitiesExist_whenRetrievingLastPage_thenCorrect() {
+        final int pageSize = 10;
+        final Query queryTotal = entityManager.createQuery("Select count(f.id) from Foo f");
+        final long countResult = (long) queryTotal.getSingleResult();
+
+        final Query query = entityManager.createQuery("Select f from Foo as f order by f.id");
+        final int lastPage = (int) ((countResult / pageSize) + 1);
+        configurePagination(query, lastPage, pageSize);
+        final List<Foo> fooList = query.getResultList();
+
+        // Then
+        assertThat(fooList, hasSize(lessThan(pageSize + 1)));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public final void givenEntitiesExist_whenRetrievingPage_thenCorrect() {
+        final int pageSize = 10;
+
+        final Query queryIds = entityManager.createQuery("Select f.id from Foo f order by f.lastName");
+        final List<Integer> fooIds = queryIds.getResultList();
+
+        final Query query = entityManager.createQuery("Select f from Foo e whet f.id in :ids");
+        query.setParameter("ids", fooIds.subList(0, pageSize));
+        final List<Foo> fooList = query.getResultList();
+
+        // Then
+        assertThat(fooList, hasSize(pageSize));
+    }
+
+    @Test
+    public final void givenEntitiesExist_whenRetrievingPageViaCriteria_thenCorrect() {
+        final int pageSize = 10;
+        final CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
+        final CriteriaQuery<Foo> criteriaQuery = criteriaBuilder.createQuery(Foo.class);
+        final Root<Foo> from = criteriaQuery.from(Foo.class);
+        final CriteriaQuery<Foo> select = criteriaQuery.select(from);
+        final TypedQuery<Foo> typedQuery = entityManager.createQuery(select);
+        typedQuery.setFirstResult(0);
+        typedQuery.setMaxResults(pageSize);
+        final List<Foo> fooList = typedQuery.getResultList();
+
+        // Then
+        assertThat(fooList, hasSize(pageSize));
+    }
+
+    @Test
+    public final void givenEntitiesExist_whenRetrievingPageViaCriteria_thenNoExceptions() {
+        int pageNumber = 1;
+        final int pageSize = 10;
+        final CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
+
+        final CriteriaQuery<Long> countQuery = criteriaBuilder.createQuery(Long.class);
+        countQuery.select(criteriaBuilder.count(countQuery.from(Foo.class)));
+        final Long count = entityManager.createQuery(countQuery).getSingleResult();
+
+        final CriteriaQuery<Foo> criteriaQuery = criteriaBuilder.createQuery(Foo.class);
+        final Root<Foo> from = criteriaQuery.from(Foo.class);
+        final CriteriaQuery<Foo> select = criteriaQuery.select(from);
+
+        final TypedQuery<Foo> typedQuery = entityManager.createQuery(select);
+        while (pageNumber < count.intValue()) {
+            typedQuery.setFirstResult(pageNumber - 1);
+            typedQuery.setMaxResults(pageSize);
+            System.out.println("Current page: " + typedQuery.getResultList());
+            pageNumber += pageSize;
+        }
+    }
+
+    // UTIL
+
+    final int determineLastPage(final int pageSize, final long countResult) {
+        return (int) (countResult / pageSize) + 1;
+    }
+
+    final void configurePagination(final Query query, final int pageNumber, final int pageSize) {
+        query.setFirstResult((pageNumber - 1) * pageSize);
+        query.setMaxResults(pageSize);
+    }
+
+}