Implementing a JPA Dynamic Query

Using EntityManager methods createQuery or createNativeQuery, you can create a Query object dynamically at run time (see "Using Java"). Using the Query methods getResultList, getSingleResult, or executeUpdate you can execute the query (see "Executing a Query").

Optionally, you can configure your named query with query hints to use JPA persistence provider vendor extensions (see "Configuring TopLink Query Hints in a JPA Query").

For more information, see the following:

• "Acquiring an EntityManager"

• "Creating a Dynamic Java Persistence Query Language Query With the Entity Manager"

• "Creating a Dynamic TopLink Expression Query With the EntityManager"

• "Creating a Dynamic Native SQL Query With the EntityManager"

• "Executing a Query"

Using Java

Example 8-4 shows how to create a dynamic EJB QL query with parameters and how to execute the query. In this example, the query returns multiple results so Query method getResultList is used.

Example 8-4 Implementing and Executing a Dynamic Query

Query queryEmployeeByFirstName = entityManager.createQuery(
    "SELECT OBJECT(emp) FROM Employee emp WHERE emp.firstName = :firstname"
);

queryEmployeeByFirstName.setParameter("firstName", "Joan");

Collection employees = queryEmployeeByFirstName.getResultList();