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"); 
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