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;
+    }
 }