title: Tutorial_2_The_Queries —
Queries
In these example, the variable “em” is an entity manger initialized just like it was in the first tutorial.
Empty String
Setup: None required
em.createQuery(""); Unknown Class
Setup: None required
em.createQuery("from IncorrectClassName"); Minimal “Get All”
Setup: None required
em.createQuery("from Person").getResultList(); Successfully Get a Single Object
Setup: Insert exactly 1 Person entity in the database
final Person p = (Person) em.createQuery("from Person").getSingleResult(); Unsuccessfully Try to get a Single Object When There Are None
Setup: Make sure there are no Person entities in the database
em.createQuery("from Person").getSingleResult(); Unsuccessfully Try to get a Single Object With Too Many
Setup: Insert two or more Person entities in the database
em.createQuery("from Person").getSingleResult(); Find By Primary Key
Setup: Insert a Person in the database, make sure to get the key of the object inserted
final Person p = em.find(Person.class, personKey);Unsuccessfully Find by Primary Key
Setup: None required
final Person p = em.find(Person.class, -42);Search Using Query Parameter and Storing Result as List<?>
Setup: Insert one person record where the Person’s first name = “Brett”.
final List<?> list = em.createQuery("from Person where p.firstName = ?1")
.setParameter(1, "Brett").getResultList();Search Using Query Parameter and Storing Result as List
Setup: Insert one person record where the Person’s first name = “Brett”.
final List<Person> list = em.createQuery(
"from Person where firstName = ?1").setParameter(1, "Brett")
.getResultList();Do Find by Primary Key and Queries Return == Objects
Setup: Insert one person record and store the primary key. Also make sure the first name of the person equals “Brett”.
final Person pByKey = em.find(Person.class, personKey);
final Person pByWhere = (Person) em.createQuery(
"SELECT p from Person p where firstName='Brett'")
.getSingleResult();Use Wrong Class Name
Setup: None required
em.createQuery("from PERSON").getSingleResult(); Use Wrong Field Name
Setup: None required
em.createQuery("from Person p where p.FirstName='Brett'"); Use Column Name Instead of Field Name
Setup: None required, but maybe insert a single person whose first name = “Brett”.
em.createQuery("from Person p where p.firstName='Brett'").getResultList(); Use a Parameter but Provide Wrong Index
Setup: None required
em.createQuery("from Person p where p.firstName=?1").setParameter(0, "Brett"); Set Parameter Where There are None: Version 1
Setup: None required
em.createQuery("from Person p where p.firstName='Brett'").setParameter(1, "Brett"); Set Parameter When There Are None: Version 2
Setup: None required
em.createQuery("from Person p where p.firstName='?1'").setParameter(1, "Brett"); title: Tutorial_2_The_First_Example —
Test Setup
We have a bit of setup/initialization code we need to do before we can get started. We have seen all of this code before in Tutorial 1. The difference here is that we are going to work though some refactorings to get to where we were in tutorial 1. Here are the various parts:
Configure the Logger
BasicConfigurator.configure();
Logger.getLogger("org").setLevel(Level.ERROR);Create the Entity Manager Factory
final EntityManagerFactory emf = Persistence
.createEntityManagerFactory("examplePersistenceUnit");Create the Entity Manager
final EntityManager em = emf.createEntityManager();Create Entities
final Address a1 = new Address("A Rd.", "", "Dallas", "TX", "75001");
final Person p1 = new Person("Brett", 'L', "Schuchert", a1);
final Address a2 = new Address("B Rd.", "S2", "OkC", "OK", "73116");
final Person p2 = new Person("FirstName" + System.currentTimeMillis(),
'K', "LastName", a2);Use the Entity Manager
em.getTransaction().begin();
em.persist(p1);
em.persist(p2);
em.flush();Perform a Query and Verify it Works
final int numberFound = em.createQuery("Select p from Person p")
.getResultList().size();
assertEquals(2, numberFound);The Whole Thing
Here’s all of this put together. Note that we’re going to refactor this heavily coming up.
package entity;
import static org.junit.Assert.assertEquals;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.junit.Test;
public class JpaApiTests {
@Test
public void example1InsertTwoPeople() {
BasicConfigurator.configure();
Logger.getLogger("org").setLevel(Level.ERROR);
final EntityManagerFactory emf = Persistence
.createEntityManagerFactory("examplePersistenceUnit");
final EntityManager em = emf.createEntityManager();
final Address a1 = new Address("A Rd.", "", "Dallas", "TX", "75001");
final Person p1 = new Person("Brett", 'L', "Schuchert", a1);
final Address a2 = new Address("B Rd.", "S2", "OkC", "OK", "73116");
final Person p2 = new Person("FirstName" + System.currentTimeMillis(),
'K', "LastName", a2);
em.getTransaction().begin();
em.persist(p1);
em.persist(p2);
em.flush();
final int numberFound = em.createQuery("Select p from Person p")
.getResultList().size();
assertEquals(2, numberFound);
}
}Get it Running
After creating your Test Class, verify that it runs and that this test passes:
- Right-click anywhere in your class’ editor pane.
- Select Run As:JUnit Test
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