DEPRECATED ch19 JPAContainer

Since Vaadin 8 DataProvider is to be used instead of container

Overview

Implements Container interface

Supports especially EclipseLink implementation of JPA and Hibernate

JPA:

• EntityManager is the main interface
• JPQL the query language
• or native SQL
• or Criteria API (JPA 2.0)

Apache License 2.0 (free for non-commercial use)

JPAContainer concepts

• EntityProvider interface - data access is handled, different entity providers provided
• by default unbuffered - changes are written immediately when setValue() is called or user edits a bound field
• batchable containers can be set as buffered, changes are written on calling commit()
  • item level buffering : when updating item property values
  • container level : when adding or deleting items
  • OptimisticLockException can be thrown
• documentation
  • API documentation
  • tutorial
  • AddressBook demo
  • demo

Installing

• download and install, or
• as Maven dependency, or
• create as Maven archetype

Defining domain model

• Entity
  • implements Serializable interface
  • default constructor
• Metadata (by javax.persistence annotation or XML)
  • more, see JPA

Basic usage

• Create JPAContainer
  • JPAContainerFactory provides various make...() methods, takes class type of entity class as first parameter, and second class being a persistence unit name (persistence context) or an EntityManager instance
    • make() - uses CachingMutableLocalEntityProvider
    • makeReadOnly() - CachingLocalEntityProvider
    • makeBatchable() - BatchableLocalEntityProvider
    • makeNonCached() - MutableLocalEntityProvider
    • makeNonCachedReadOnly() - LocalEntityProvider
  • obtain EntityManager - JPAContainerFactory.createEntityManagerForPersistenceUnit("book-examples")
  • create manually (not normally do this, but when need to use a custom entity provider or extend JPAContainer)
• Creating and accessing entities
  • addEntity() returns a new ID; then getItem(itemId)
  • Item
    • getItem() - gets the Item
    • getEntity() - gets the entity object
    • states:
      • persistent : is it actually persistent, i.e. fetched from a database
      • modified (item buffering) : has changed and not yet committed, only when setBuffered(true) for item
      • dirty (container buffering) : has been modified after fetched, possible only when buffering enabled for container
      • deleted (container buffering) : been marked for deletion
  • Refreshing
    • if item changed outside container (directly through EntityManager) or changed in database, need to refresh
    • refresh() : discards all caches and buffers, refreshes all loaded items, changes discarded
    • refreshItem() : refresh single item
• Nested Properties
  • can do with one-to-one or many-to-one relationship
  • addNestedContainerProperty() with dot-separated path
• Hierarchical Container (JPAContainer implements Container.Hierarchical)
  • needs a parent ID column in database

Entity providers

• they are essentially wrappers over JPA entity manager with optimizations and other features for different scenarios
• if uses factory make...() methods, the choice is largely invisible
• built-ins
  • overview
    • caching : better performance, more memory usage, makes provider stateful
    • batching : running updates in larger batches, enhance performance and used with caching
    • read-only : preferable when only read
    • CachingMutableLocalEntityProvider (make()) : first choice for read-write
    • CachingLocalEntityProvider (makeReadOnly) : first choice for read only
  • LocalEntityProvider (makeNonCachedReadOnly) - read-only, laze loading, no caching, read directly from entity manager
  • MutableLocalEntityProvider - extend LocalEntityProvider with write support; all changes send to entity manager directly
    • provider handle transaction - default
    • container handle transaction - extend the clas and annotate it
    • change event can be listened
  • BatchableLocalEntityProvider : non-caching implementation of BatchableEntityProvider
  • CachingLocalEntityProvider (makeReadOnly) : read-only, lazy loading, caches entities and query results, cache size can be configured, can be manually flushed
  • CachingMutableLocalEntityProvider : like above but writable, when an entity is added or updated, cache is flushed; when entity is removed, affected caches flushed; perhaps most commonly used
  • CachingBatchableLocalEntityProvider : supports batch updates; need to implement a BatchUpdateCallback that does all updates, an extension of the above; work properly if entities do not contain any references to other entities that are managed by the same container
• built-ins for JEE environment
  • Entity providers in com.vaadin.addon.jpacontainer.provider.jndijta works mostly the same but use JNDI lookups to get EntityManager and JTA transaction
• Entity providers as enterprise (session) beans
  • usage
    • allow server injection
    • use JTA (java transaction API)
    • just extend and annotate
    • stateless (no caching) or stateful (if extends a caching entity provider)
    • see an example

Filtering

Query

Automatic form generation

Use with Hibernate