more queries using QueryDSL

querydsl/src/main/java/org/baeldung/dao/PersonDaoImpl.java

@@ -1,13 +1,18 @@
 package org.baeldung.dao;
 
+import com.mysema.query.group.GroupBy;
 import com.mysema.query.jpa.impl.JPAQuery;
+import com.mysema.query.jpa.impl.JPAQueryFactory;
 import org.baeldung.entity.Person;
 import org.baeldung.entity.QPerson;
 import org.springframework.stereotype.Repository;
 
+import javax.inject.Provider;
 import javax.persistence.EntityManager;
 import javax.persistence.PersistenceContext;
+import javax.persistence.Tuple;
 import java.util.List;
+import java.util.Map;
 
 @Repository
 public class PersonDaoImpl implements PersonDao {
@@ -20,6 +25,7 @@ public class PersonDaoImpl implements PersonDao {
         return person;
     }
 
+    @Override
     public List<Person> findPersonsByFirstnameQueryDSL(String firstname) {
         JPAQuery query = new JPAQuery(em);
         QPerson person = QPerson.person;
@@ -27,4 +33,38 @@ public class PersonDaoImpl implements PersonDao {
         return query.from(person).where(person.firstname.eq(firstname)).list(person);
     }
 
+    @Override
+    public List<Person> findPersonsByFirstnameAndSurnameQueryDSL(String firstname, String surname) {
+        JPAQuery query = new JPAQuery(em);
+        QPerson person = QPerson.person;
+
+        return query.from(person).where(person.firstname.eq(firstname).and(
+                person.surname.eq(surname))).list(person);
+    }
+
+    @Override
+    public List<Person> findPersonsByFirstnameInDescendingOrderQueryDSL(String firstname) {
+        JPAQuery query = new JPAQuery(em);
+        QPerson person = QPerson.person;
+
+        return query.from(person).where(person.firstname.eq(firstname)).orderBy(
+                person.surname.desc()).list(person);
+    }
+
+    @Override
+    public int findMaxAge() {
+        JPAQuery query = new JPAQuery(em);
+        QPerson person = QPerson.person;
+
+        return query.from(person).list(person.age.max()).get(0);
+    }
+
+    @Override
+    public Map<String, Integer> findMaxAgeByName() {
+        JPAQuery query = new JPAQuery(em);
+        QPerson person = QPerson.person;
+
+        return query.from(person).transform(GroupBy.groupBy(person.firstname).as(GroupBy.max(person.age)));
+    }
+
 }

querydsl/src/main/java/org/baeldung/entity/Person.java

@@ -15,6 +15,9 @@ public class Person {
     @Column
     private String surname;
 
+    @Column
+    private int age;
+
     Person() {
     }
 
@@ -23,6 +26,11 @@ public class Person {
         this.surname = surname;
     }
 
+    public Person(String firstname, String surname, int age) {
+        this(firstname, surname);
+        this.age = age;
+    }
+
     public Long getId() {
         return id;
     }
@@ -47,4 +55,11 @@ public class Person {
         this.surname = surname;
     }
 
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
 }

querydsl/src/test/java/org/baeldung/dao/PersonDaoTest.java

@@ -10,6 +10,8 @@ import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 import org.springframework.test.context.transaction.TransactionConfiguration;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.util.Map;
+
 
 @ContextConfiguration("/test-context.xml")
 @RunWith(SpringJUnit4ClassRunner.class)
@@ -30,4 +32,48 @@ public class PersonDaoTest {
         Person personFromDb = personDao.findPersonsByFirstnameQueryDSL("Kent").get(0);
         Assert.assertEquals(person.getId(), personFromDb.getId());
     }
+
+    @Test
+    public void testMultipleFilter() {
+        personDao.save(new Person("Erich", "Gamma"));
+        Person person = personDao.save(new Person("Ralph", "Beck"));
+        Person person2 = personDao.save(new Person("Ralph", "Johnson"));
+
+        Person personFromDb = personDao.findPersonsByFirstnameAndSurnameQueryDSL("Ralph", "Johnson").get(0);
+        Assert.assertNotSame(person.getId(), personFromDb.getId());
+        Assert.assertEquals(person2.getId(), personFromDb.getId());
+    }
+
+    @Test
+    public void testOrdering() {
+        Person person = personDao.save(new Person("Kent", "Gamma"));
+        personDao.save(new Person("Ralph", "Johnson"));
+        Person person2 = personDao.save(new Person("Kent", "Zivago"));
+
+        Person personFromDb = personDao.findPersonsByFirstnameInDescendingOrderQueryDSL("Kent").get(0);
+        Assert.assertNotSame(person.getId(), personFromDb.getId());
+        Assert.assertEquals(person2.getId(), personFromDb.getId());
+    }
+
+    @Test
+    public void testMaxAge() {
+        personDao.save(new Person("Kent", "Gamma", 20));
+        personDao.save(new Person("Ralph", "Johnson", 35));
+        personDao.save(new Person("Kent", "Zivago", 30));
+
+        int maxAge = personDao.findMaxAge();
+        Assert.assertTrue(maxAge == 35);
+    }
+
+    @Test
+    public void testMaxAgeByName() {
+        personDao.save(new Person("Kent", "Gamma", 20));
+        personDao.save(new Person("Ralph", "Johnson", 35));
+        personDao.save(new Person("Kent", "Zivago", 30));
+
+        Map<String, Integer> maxAge = personDao.findMaxAgeByName();
+        Assert.assertTrue(maxAge.size() == 2);
+        Assert.assertSame(35, maxAge.get("Ralph"));
+        Assert.assertSame(30, maxAge.get("Kent"));
+    }
 }