org.minijax.data

Class BaseDao

java.lang.Object

org.minijax.data.BaseDao

All Implemented Interfaces:

Closeable, AutoCloseable

public abstract class BaseDao
extends Object
implements Closeable

The Dao class is the interface for all database access.

Field Summary

Fields

Modifier and Type	Field and Description
protected javax.persistence.EntityManager	em

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BaseDao(javax.persistence.EntityManagerFactory emf)

Method Summary

Modifier and Type	Method and Description
void	close()
<T extends BaseEntity> long	countAll(Class<T> entityClass) Counts all rows of a type.
<T extends BaseEntity> T	create(T obj) Inserts a new instance in the database.
<T extends BaseEntity> void	delete(T obj) Soft deletes an object.
protected static <T extends BaseEntity> T	firstOrNull(List<T> list) Returns null if the list is empty.
<T extends BaseEntity> void	purge(T obj) Hard deletes an object.
<T extends BaseEntity> T	read(Class<T> entityClass, UUID id) Retrieves an object by ID.
<T extends NamedEntity> T	readByHandle(Class<T> entityClass, String handle) Finds a user by handle.
<T extends BaseEntity> List<T>	readPage(Class<T> entityClass, int page, int pageSize) Returns a page of objects.
<T extends BaseEntity> T	update(T obj) Updates an object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

em

protected javax.persistence.EntityManager em

Constructor Detail

BaseDao

protected BaseDao(javax.persistence.EntityManagerFactory emf)

Method Detail

create

public <T extends BaseEntity> T create(T obj)

Inserts a new instance in the database.

Parameters:

obj - The object to create.

Returns:

The instance with ID.

read

public <T extends BaseEntity> T read(Class<T> entityClass,
                                     UUID id)

Retrieves an object by ID.

Parameters:

id - The ID.

Returns:

The object if found; null otherwise.

readByHandle

public <T extends NamedEntity> T readByHandle(Class<T> entityClass,
                                              String handle)

Finds a user by handle. Returns the user on success. Returns null on failure.

Parameters:

handle - The user's handle.

Returns:

The user on success; null on failure.

readPage

public <T extends BaseEntity> List<T> readPage(Class<T> entityClass,
                                               int page,
                                               int pageSize)

Returns a page of objects.

Parameters:

entityClass - The entity class.

page - The page index (zero indexed).

pageSize - The page size.

Returns:

A page of objects.

update

public <T extends BaseEntity> T update(T obj)

Updates an object.

Parameters:

obj - The object to update.

delete

public <T extends BaseEntity> void delete(T obj)

Soft deletes an object. The data is still in the database, but with deleted flag.

Parameters:

obj - The object to delete.

purge

public <T extends BaseEntity> void purge(T obj)

Hard deletes an object. This purges the data from the database.

Parameters:

obj - The object to delete.

countAll

public <T extends BaseEntity> long countAll(Class<T> entityClass)

Counts all rows of a type.

Parameters:

entityClass - The entity class.

Returns:

The count of rows.

close

public void close()

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

firstOrNull

protected static <T extends BaseEntity> T firstOrNull(List<T> list)

Returns null if the list is empty. Returns the first element otherwise. JPA getSingleResult() throws an exception if no results, which is an annoying design. So instead you can call getResultList() and wrap it with firstOrNull(), which is the more expected result.

Parameters:

list -

Returns: