Compare And Contrast Persistence Frameworks Computer Science

Compare And Contrast Persistence Frameworks Computer Science

Compare And Contrast Persistence Frameworks Computer Science

Compare and contrast the following persistence frameworks: Java Persistence API (JPA), Hibernate and Java Database Connectivity. What improvements were made in EJB3.1 and JPA2? Include topics of scalability, security, connection pools, connection factories, entity management, transactional context, query languages, ORM, JCA, JNDI, the DAO-VO design pattern and specifically persistence layer(s) on a distributed n-tier enterprise platform in your discussion.

HQL is a language for talking about "sets of objects." It unifies relational operations with object models. It makes SQL be object oriented. It uses classes and properties instead of tables and columns. It supports polymorphism, associations, and is much less verbose than SQL.Other features include: Full support for relational operations, Inner/outer/full joins, cartesian products, Projection, Aggregation (max, avg) and grouping, Ordering, Subqueries, SQL function calls[7]

We need to create a DTO class which represents a single row of the table of the database. It must be a class which follows the Javabean specifications. That is, having a (implicit) no-arg constructor, having private properties which are exposed by public getters and setters, having the Object#equals() implemented and finally the class must also be able to implement java.io.Serializable.[14]. JDBC drivers report all error situations by raising the SQLException. SQLException is a checked exception, therefore developers are forced to handle it-even though it isn’t possible to recover from the majority of these exceptions, which results in cluttering the code. Moreover, the error code and message obtained from the SQLException object are database vendor-specific, so it’s not possible to write portable DAO error messaging code.

Hibernate and JPA

The first step to using the DAO classes is to obtain the specific DAO factory we will need to use in storing and loading objects. The purpose of the specific DAO factories is to implement the abstract methods defined in the abstract DAO class, which will return the DAO objects for each type we need to persist. Most users of the DAO pattern agree that the best option is to do as little exception handling as possible in the DAO class and instead allow the business object to handle errors. Thus, you might just rethrow any exception that occurs in the DAO class.

What improvements were made in EJB3.1 and JPA2

Improvements in EJB 3.1

With EJB 3.1, there is no need to define home/local interfaces. Now EJB can be defined simple with an annotation.

Singleton beans were introduced with EJB 3.1. Singleton beans can be used for shared data at application level.

Asynchronous EJB calls are now supported with @Asynchronous method-level annotation.

Packaging and deployment can be directly done in a war file.

Session beans with a local view can be accessed without a separate local business interface.

EJB Timer Service enhancements are also included to support cron-like scheduling, deployment-time timer creation, and Stateful Session Bean timed objects.

Embedded container: A new embeddable API is available for executing EJB components within a Java SE environment (for unit testing, batch processing, etc.).

EJB Lite: This definition of a lightweight subset of functionalities can be provided within Java EE Profiles (such as the Java EE Web Profile).

Portable JNDI name: The syntax for looking up EJB components is now specified.

Improvements in JPA 2.0

Collections of basic types.

Collections of embeddable.

Maintaining a persistent ordering is now possible with the @OrderColumn annotation.

Orphan removal that allows removal of child object when parent object is removed.

Pessimistic locking has also been introduced along with optimistic locking.

JPA 2.0 also introduced foreign key mappings for unidirectional one-to-many relationships.

Improved support for maps. Maps can now have keys and values of basic types,

entities, or embeddables.

Criteria query API which allows queries to constructed in an object-oriented manner.

Improvements in JPQL syntax.

Embeddable objects can now be nested into other embeddable objects and have relationships to entities.

The dot (.) navigation syntax has been extended to handle embeddables with relationships and embeddables of embeddables.

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