JPA's EntityManager createQuery() vs createNamedQuery() vs createNativeQuery()

Question

Can anyone please explain me the differences between following methods of JPA's EntityManager:

• createQuery()
• createNamedQuery()
• createNativeQuery()

And also explain to me in which cases we should use which method?

Answer 1

• The createQuery method is used to create dynamic queries, which are queries defined directly within an application’s business logic. Example:

  public List findWithName(String name) { return em.createQuery( "SELECT c FROM Customer c WHERE c.name LIKE :custName") .setParameter("custName", name) .setMaxResults(10) .getResultList(); } 

• The createNamedQuery method is used to create static queries, or queries that are defined in metadata by using the javax.persistence.NamedQuery annotation. The name element of @NamedQuery specifies the name of the query that will be used with the createNamedQuery method. The query element of @NamedQuery is the query:

  @NamedQuery( name="findAllCustomersWithName", query="SELECT c FROM Customer c WHERE c.name LIKE :custName" ) 

Here’s an example of createNamedQuery, which uses the @NamedQuery:

    @PersistenceContext     public EntityManager em;     ...     customers = em.createNamedQuery("findAllCustomersWithName")     .setParameter("custName", "Smith")     .getResultList(); 

• The createNativeQuery Create an instance of Query for executing a native SQL statement. here are some reasons to choice createNativeQuery:

  • Low level access, which means that you can optimize and handle the mapping by yourself; with SQL you actually access the database table while with JPQL you access the entity objects;
  • Maybe you do not want to learn JPQL if you already know SQL
  • You already have the queries written in SQL, and do not have resources/time to port them to JPQL

For more details visit those links:

Creating Queries Using the Java Persistence Query Language

JPA why use createNamedQuery

Why do we need to create native query?