Entity Manager Operations

Use

Basic Operations

Type	Method and operation
Basic Operations
`void`	`persist(Object entity)` Make an entity instance managed and persistent.
`<T> T`	`find(Class<T> entityClass, Object primaryKey)` Find by primary key.
`<T> T`	`merge(T entity)` Merge the state of the entity with the current persistence context.
`void`	`remove(Object entity)` Remove the entity instance.
Basic Query Operations
`Query`	`createNamedQuery(String name)` Create an instance of Query for executing a named query (in JPQL or Native SQL).
`Query`	`createQuery(String qlString)` Create an instance of Query for executing a JPQL statement.
Advanced Query Operations
`Query`	`createNativeQuery(String sqlString, Class resultClass)` Create an instance of Query for executing a Native SQL query.
`Query`	`createNativeQuery(String sqlString, String resultSetMapping)` Create an instance of Query for executing a Native SQL query.
`Query`	`createNativeQuery(String sqlString)` Create an instance of Query for executing a Native SQL statement, for example, for update or delete.
`FlushModeType`	`getFlushMode()` Get the flush mode that applies to all objects within the persistence context.
`void`	`setFlushMode(FlushModeType flushMode)` Set the flush mode that applies to all objects within the persistence context.
Synchronization with the Database
`void`	`flush()` Synchronize the persistence context with the underlying database.
`void`	`refresh(Object entity)` Refresh the state of the instance from the database, overwriting any changes made to the entity.
Contents of the Persistence Context
`boolean`	`contains(Object entity)` Check if the entity instance belongs to the current persistence context.
`void`	`clear()` Clear the persistence context, causing all managed entities to become detached.
Life Cycle of the Entity Manager
`void`	`close()` Close an application-managed Entity Manager.
`boolean`	`isOpen()` Determine whether the Entity Manager is open.
Concurrency Control
`void`	`lock(Object entity, LockModeType lockMode)` Set the lock mode for an entity object within the persistence context.
Transactions
`EntityTransaction`	`getTransaction()` Returns the resource-level transaction object.
`void`	`joinTransaction()` Indicate to the Entity Manager that a JTA transaction is active.
Other
`<T> T`	`getReference(Class<T> entityClass, Object primaryKey)` Get an instance which allows lazy fetching of its state.
`Object`	`getDelegate()` Return the underlying provider object for the Entity Manager, if available.