Review on JPA Based ORM Data Persistence Framework



Abstract—

Large scale application design and development

involve some critical decisions. One of the most important issue

that affects software application design and development is the

technology stack used to develop such large systems. System

response time measures how quickly an interactive system

responds to user input. Programming tools like Object Rela-

tional Mapping (ORM) is used to handle the communication

between object model and data model components which is vital

for such systems. Currently, Hibernate is considered the most

flexible ORM frameworks and has become the de facto

standard for JPA-based data persistent frameworks. This

article reviews the most widely used ORM providers, especially

frameworks that provide support for Java Persistence API

(JPA) like Hibernate JPA, EclipseLink, OpenJPA and Data

Nucleus.

Index Terms—

Hibernate, eclipselink, openjpa, data nucleus.

I. INTRODUCTION

Object/Relational Mapping (ORM) is a technique to

transmute data from an object-oriented model into the

relational database model. Object-Oriented Programming

(OOPs) is based on entities, whereas the relational databases

management system (RDBMS) sordid on relations and fields

to store data. Fig. 1 shows the mapping process between the

java classes and the relations database. Interpretation of the

java entities into the relational database requires

interoperability among the disparate architectures. In order to

obviate mapping worriment, ORM bridges the gap between

the plat- forms and manage the disparity between the object

graphs and the structured query language (SQL). For a

developer, segregated mapping layer deprecates the

complexity of the boilerplate code [1]. ORM wraps the

functionality of an old conventional Java Database

Connectivity (JDBC) programming model [2] into the

persisted databases. A conventional ORM application

propounds a lightweight object-oriented interface called the

Data Access Object (DAO) [2]. A DAO layer determines the

designing pattern that encapsulates the java entities into a

sequence of SQL operations (e.g. Insert, Delete or Update)

through predefined functions. To execute a query and

retrieve the relational data efficiently in the object-oriented

programming, a language called DQL (Doctrine Query

Language) [3] was introduced to reduce the complexity of the

user by simple data definition language (DDL) commands.

DQL is a distinguishable platform to retrieve the java entities

using predefined set of protocols. Apart from the obvious

Manuscript received March 6, 2017; revised June 16, 2017.

Neha Dhingra, Emad Abdelmoghith, and Hussien T. Mouftah are with the

Department of Electrical Engineering and Computer Science, University of

Ottawa, Canada (e-mail:{ndhin017, eabdelmo and mouftah}@uottawa.ca).

programming convention, ORM accelerate the optimization

process through transaction locking and maintain data writes

through defined transactional [3] boundaries. Moreover,

ORM attunes data accessed in a record-based patterns. ORM

standardized the persistence process as through the java

persistence API (JPA) interface. JPA is a java application

programming interface [4] that manages the data between the

java objects and the relational databases. JPA is a

specification, not an implementation to persist data in the

RDBMS. Due to the failure of the enterprise persistence

model and lack of java persistence standard, developers often

materialized JPA implementations as an attempt to optimize

the mapping architecture. JPA implementations increase the

portability and extensibility of the code, by de-coupling the

JPA specifications from the underlying API architecture. The

next couple of sections discuss a comparison based on JPA

and JPA implementation, which would decompose the view

of a developer to formalize the approach while developing an

API [1]-[4].

II. JPA PROVIDERS

Java Persistence API (JPA) is an interface that persists the

java entity to the relational database [5]. A JPA specification

is a set of empty methods and collection of interfaces that

only describe java persistence methodologies and provides

standardized programming through the JPA implementation.

According to Ogheneovo et al. JPA is a standard-compliant

framework defined for mapping plain old java object (POJO)

into the relational databases. Currently, most of the JPA

persistence providers have released several commercial [5]

and open [5] source JPA implementations. For instance

Hibernate by JBOSS and RedHat [6], EclipseLink by Oracle

and sun glassfish project [7], OpenJPA by IBM and Bea [8]

and Data Nucleus by JPOX and Tapestry [9]; are some of the

commercially available and vendor independent providers

that rigorously follow JPA paradigm in order to configure an

API.

Developing an API based on the appropriate JPA

implementation is determined by three potentials prospects.

Firstly, it is the compatibility between the relational database

and the JPA provider, which is based on the complexity of

the SQL operations i.e triggers, indexes, stored procedures.

Second, it is the precipitancy of building a prototype which is

based on the affordance of the API that means the ease at

which a developer of an API performed operations. Finally,

the middlewares [9] adopted, while building the mapping

strategy. For example, JBoss is a middleware software for

Hibernate API. According to Miki Enoki et al. [9]

middleware is software that combines the software

component or enterprise application; it is a layer that lies

between the OS and the API. To map the data into database,

Neha Dhingra, Emad Abdelmoghith, and Hussien T. Mouftah

Review on JPA Based ORM Data Persistence Framework

International Journal of Computer Theory and Engineering, Vol. 9, No. 5, October 2017

318

DOI: 10.7763/IJCTE.2017.V9.1160

JPA performs metadata modeling and schema creation which

then is accomplished by standard annotations by defining

@annotationname or via the XML files using tags.

Annotations are acknowledged as an exemplary alternative to

XML because of the ease of programming. Both mapping

techniques follow similar functionality but due to the high

complexity in the XML, it is not preferred much in the

programming of an API. For example, an annotation/XML

tag to create a primary key column in an entity is defined by

@ID in the annotations and in XML the syntax is

<name=”ID” value=”integer”/>. A typical, JPA API defines

run-time interface objects to persist data and to create a

connection. JPA exemplify boilerplate code at run-time by

instantiation of pre-defined interfaces. To create a connection

between the java objects and the database, JPA defines an

interface object called the EntityManagerFactory [10]. This

object performs allocation and de-allocation of the resources.

Once the mapping process is completed, the manager is

destroyed and the resources are detached. An

EntityManagerFactory object is invoked by the object of an

EntityManager interface. The EntityManager then interact

within a persistence context to perform create, read, update

and delete (CRUD) operations on the entities.

The persistence process in JPA manages the SQL

operation through the transaction and query objects to

retrieve and execute data definition language (DDL)

operations. Fig. 2 outlined a three layers high-level

architecture where the top-most layer is the graphical user

interface (GUI) that communicates with the client and server

in order to perform operations on the front-end. The middle

layer is the JPA Layer; it is divided into the service layer

using controllers, data access objects (DAO), repositories

and service implementation, the second layer in the JPA layer

is called the data persistence layer. The persistence layer

defines the mapping procedure between the relational

database and the java entities. The bottom layer determines

the type of RDBMS in order to persist data in the tabular

format. According to [10] a typical JPA implementation also

support spatial and geographical data storage for persistence

[5]-[10].

A. Hibernate

Hibernate is a vendor independent ORM framework; it

maps the java object-oriented model into the relational

database by directly persisting access between the plain old

java objects and the relational database. According to [11];

hibernate manages to provides high performance, feature rich

mapping technology to persist java data types into the

underlying structured query language (SQL) data types. For

example, an integer field in java class is converted into int

(integer) column in the Microsoft SQL Server. Hibernate

being a comprehensive solution accomplish persistence by

not only taking responsibility for mapping the java entities to

the database tables but also overcoming the development

time contrarily wasted on binding a java API through java

database connectivity (JDBC). In a study by Bhushan S.

Sapre et al. in discussed that Hibernate’s mapping process

utilize run-time persistence properties to create an association

between the java classes and the relational fields, in order to

avoid impedance mismatch problem.

Because hibernate is a free software it is distributed under

the GNU Lesser General Public License 2.1 [12]; it is an

optimal solution for resource-oriented APIs. The mapping

process in Hibernate is based on the lazy load, which means

all the necessary information about the generating the schema,

creating a sub for a java source file creating primary-foreign

key relationships between the entities. In the same study

Bhushan S. Sapre et al. in [12] also stated that hibernate

follows high- level abstraction by encapsulating the

underlying architecture of the API from the developer, which

diminishes the complexity of the code to fewer methods and

interfaces. The process increases the extensibility of the code

but constrains the knowledge of the developer to abstract

methodologies. Another study by Nisha Sharma et al. in [13]

on Hibernate manages to provide a details assessment on

queries to the database through Hibernate Query Language

(HQL) [13]. HQL is an advanced query language to retrieve

objects from the java classes and execute complex SQL

operation.

Fig. 1. Java ORM architecture.

Fig. 2. JPA architecture.

In another study by B.vasavi et al. [14]; stated that

configuration object in Hibernate is the first object, which

comprises of the properties about the connection to be

configured. The configuration object addresses and

authenticates the properties of Hibernate by creating a

connection to the database. A configuration file is used by the

SessionFactoryManager to start the persistence process and

create the connection between the java entities and the

database tables. The ses- sionFactoryManager object is

invoked then by the session instance to execute SQL

operation. In this process the session, object maintains the

cache and needs an explicit close() method in order to avoid

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memory leaks. To perform transactions on the database, a

session object is used to invoke the transaction object. The

transaction objects in Hibernate execute operations in a

particular session through transaction manager and the

underlying query. In another study by B.Vasavi et al. [14]

also stated that Hibernate allows developers to create an

efficient business application either using annotations or

XML files. In annotations, the functionalities are injected to

map the java entities into the relational tables whereas in

XML the same operation is performed through complex tags.

Because of the flexibility in practicing annotations, Hibernate

manages to override the existing mapping scenarios by

mapping enum into the columns of the database and also

outline a single property in the java entity to multiple

columns in the back- end (RDBMS). In order to standardized

Hibernate API, JPA created standard interfaces to implement

programming that is platform independent. Hibernate API is

a fully complaisant with Technology Compatibility Kit (TCK)

[15] to accomplish database modeling in JPA. According to

[14] with the rapid advancement of the web application,

Hibernate has been receiving a great consideration as a

platform independent portable language along with the

spring framework; it pro- vides a persistence layer for a

complex enterprise application with spring that act as a

template to encapsulate Hibernate sessions into the template

methods [15]. According to Jorge Edison Lascano, Hibernate

comprehend Persistence.XML configuration file to initialize

the properties of a JPA project, using the

org.hibernate.ejb.Hibernate Persistence provider. A typical

Java Platform, Standard Edition (Java SE) through [16] JPA

persist databases using the Entity Manager Factory object; it

is a static method to initialize the persistence process. An

Entity Manager Factory object is similar to the Session

Factory Object in Hibernate. In an API, requests are made to

invoke the java entities for persistence because the

EntityManager performs the basic CRUD operations by

invoking the object of Entity Factory Manager instance. The

following Fig. 3 and Fig. 4 describes Hibernates high-level

architecture to describe ORM mapping using the session or

Entity Manager Object. After which Hibernate configures

connection management using the Entity Manager Factory or

Session Manager Factory object. However, the transaction

and query management objects in Hibernate provides the

capabilities to perform run-time data retrieval operations to

execute queries, but being an over ambitious process this

creates memory overheads. According to the several studies

and books on JPA 2.1, Hibernate JPA facilitates additional

functionality to a native API through advanced

object-oriented programming. These OOPS concepts

enhanced the functionality of a conventional API by handling

inheritance and polymorphism through the implicit super

class mapping and platform independent Java Persistence

Query Language (JPQL) [11]-[16].

B. EclipseLink

In a study by Lukas Sembera [2] on JPA implementation, it

was reviewed that EclipseLink’s advanced database

extensions through the SQL compliant features such as

stored procedures, native SQL queries, and indexes improved

the efficiency of the API. EclipseLink or Eclipse Persistence

Service project [14] is a vendor independent performance

oriented ORM solution. EclipseLink being a sophisticated

JPA provider started as Oracle’s TopLink product and was

adopted by java community as an API. The evolution of

EclipseLink as an open source solution has been enabling the

developers to build an efficient application. In [15] Doug

Clarke asserted that currently EclipseLink provides ORM

mapping solution with JPA, by binding Object-XML Moxy

(with support for JAXB) and SDO (Service Data Objects)

methods and interfaces. These mapping process increases the

reliability of the API by allowing the developer to learn one

language and perform tasks in every implementation based

on the same platform. Therefore, EclipseLink JPA performs

persistence process through extended annotations or XML

files, using org.eclipse.persistence.annotations [15] packages.

In a similar study in [15] it was stated that EclipseLink also

delivers not one but a set of runtime API services through the

EntityManager class, which persist in the Javax.persistence

[16] package. The persistence process in EclipseLink is

based on built-in libraries in Eclipse IDE, which decreases

the complexity to manage JAR files explicitly and also

diminishes the compatibility issues in the API. EclipseLink

being defined as a comprehensive JPA ORM solution which

as stated in [16] delivers persistence services to the

developers through an efficient applications that access the

data in a variety of formats and data sources. Because

EclipseLink has been an experienced advanced ORM

mapping technique EclipseLink JPA manages the complex

relational databases operations progressively. In a similar

study Doug Clarke also added that mapping techniques have

evolved over the period of 12 years in EclipseLink resulting

in a domain model to create a detailed schema sordid on

cloud. EclipseLink being a commercial as well as

open-source framework sup- port advanced tools which are

independent of the under- lying implementation.

Furthermore, EclipseLink also sup- ports extended runtime

API through command-line with packages like org.eclipses.

persistence.pa [16]. Apart from existing features,

EclipseLink JPA also supports advanced functionalities such

as coordinated shared cache, clustered databases on RDBMS

or Non-relational database. Weaving not only added an

enhancement process in the API to enhance the java entities

in order to retrieve data from and into the database, but it also

configures the enhancements of the java classes to track for

lazy loads and changes in the fetch data groups to perform

internal optimization [16]. By Default, EclipseLink supports

run-time enhancement because it allows the entities to

efficiently enforce primary key-foreign key [16]

relationships and manage joins among two or more entities.

In another study on EclipseLink in [17]; developers managed

coordinated shared caching in EclipseLink, which allowed

consistency among distributed APIs with multiple

persistence units. The mapping process in EclipseLink

according to [17] is divided into following classes; A Project

class: It is a container to persists mapping and configures

metadata. In addition, to existing JPA interface support,

EclipseLink weaving technique simplified the manipulation

process by using bytecode [18] which were processed at

run-time or compile time. A Descriptor: It contains mapping

information for each data member that EclipseLink should

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persist to or transform to. A Map file: It includes a

project.XML file, and is associated with sessions that

EclipseLink can use at run-time [17] for bytecode

enhancement. Being a standard JPA implementation

EclipseLink uses the EntityManagerFactory Object to create

connection and the EntityManager object to map the java

entities to the relational database for CRUD operation. Fig. 5

describes an EclipseLink JPA high-level architecture.

Fig. 3. Hibernate JPA ORM architecture.

Fig. 4. Hibernate ORM architecture.

The persistence in EclipseLink configures the connection

with the EntityManager object which is then invoked by the

EntityManagerFactory object. Configuring a connection in

EclipseLink is a straightforward process wherein the objects

of Transaction and Query interfaces are used to retrieve and

execute complex SQL operations based on the

EntityManager object. EclipseLink also includes additional

capability called weaving while persisting data into the

database. This technique manages schema creation and map

the java classes into the relational databases to increase the

efficiency of the API [2], [15]-[18].

OpenJPA

In a study by Lukas Sembera in [2] it was stated that

OpenJPA allows developers to generate user de- fined

sequences by implementing seq interface. These Sequence

generator interfaces are used as primary key columns in an

entity. OpenJPA is an open source light-weighted JPA

implementation that is integrated with Apache server [17].

While caching in OpenJPA lack generality it has two level;

data cache that retrieves the entities loaded from the

databases and query cache that stores the primary-key

column returned in the transaction for reference [17].

Developing an OpenJPA API automates the mapping

procedure and the schema creation using

SynchronizeMapping [17] in the persistence.XML file. The

generator interfaces also in-clude additional capabilities to

store time in the primary key through the TimeseededSeq [18]

and random hex string using the UUIDHexSeq [18].

Fig. 5. EclipseLink JPA architecture.

In [19] it was asserted that by default, OpenJPA domain

model is incompetent in handling the entity constraints.

However, OpenJPA’s explicitly reconstruct constraints using

the SchemaFactory [19] property. According to OpenJPA’s

designers, a standard JPA imple- mentation essentially

depends on the monitoring of java entities, but the

specification does not define how to im plement these

monitoring [19]. However, some OpenJPA providers

auto-generate innovative sub-classes or proxy objects [20] to

improve the monitoring process explicitly, which are created

on the entity objects at the run-time. While other JPA

providers utilize byte-code weaving technologies to enhance

the actual entity class objects automatically. OpenJPA

manages run-time enhancements, by creating sub-classes,

which works subtle with the small sized API but degrades

performance and create functionality defects in a real-time

production environment. Another problem in OpenJPA was

stated in a study by Miki Enoki et al., in which it was

proposed that caching in OpenJPA is coarse- grained level

which results in a low cache hit rate [19]. An improved

caching strategy was introduced in [19] that adjusted indexes

with the fixed size at the granular level. The process

improved the performance of the cache by referencing

objects dynamically [19]. But due to some defects, in the

creating dynamic and automatic index where the frequency

of updates were high this approach failed. Thus, researchers

are still working in the OpenJPA’s cache management to

create fixed size index in the persistence layer. The process

has dividing the cache into levels and increased the cache

coordination between the java entities. However, when the

frequency of search queries are high to the database caching

manages CRUD operations before flushing the content of the

database. The second level caching supplements an extra

layer in OpenJPA by getting an overview of a particular

cache object and then eliminating the need to explicitly

handle developer’s request.

According to [18] an OpenJPA implementation persist

java classes either using annotations with property

declarations including @column, @id and @version [19] or

using XML files. The @column indicates the name of the

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column, @id defines the unique identifier similar to primary

key and @ver- sion annotation is common practice to ensures

the data integrity during merges and acts as an optimistic

concur- rency control [20]. Apart from the API, a developer

has to configure jar files such as Java. OpenJPA.All [20] and

Javax.persistence [20] packages. The persistence process

also instantiates the objects of EntityFactoryManager and

EntityManager to complete the persistence process. Entity-

FactoryManager Object is a JPA standard implementation, to

create a one-time connection while the EntityManager wraps

dynamic transactions for persistence. The diagram in Fig. 6

reviews a high-level architecture of OpenJPA by defining the

persistence process using the JPA standard specifications

through the EntityManger and the EntityFactoryManager

Object. The diagram also incorporates two-level cache

strategies in OpenJPA mainly the Query Cache and the Data

Cache to optimize the API efficiency [2], [17]-[20].

Fig. 6. OpenJPA architecture.

D. Data Nucleus

Data Nucleus is an open source java persistent framework

that the saves state [21] of the java Object into the relational

database. But entity graphs in data nucleus cache data

through generic compilation [21]; they are an initial step in

the Data Nucleus caching strategy because they are

independent of the underlying data source and create

expression tree [21]. The next process to cache the java

entities creates a ”compiled expression tree” [21], which is

then are converted into the native language of the relational

database. Finally, the executed query returns the object

cached with the ”resultant” objects According to the Data

Nucleus designing community, Data Nucleus is a fully

complaisant JPA implementation [21] providing transparent

data persistence and byte- code enhancement to persist data

in the database. Through transparent data persistence, Data

Nucleus directly manipulate data stored in the relational

database using the java entities. In Data Nucleus, the

persistence process is divided into two stages. In the first

phase enhancement process utilizes the common technique of

bytecode manipulation to create persisted java class [21].

Data Nucleus manages the enhancement using” Data Nucleus

Enhancer”; it performs manipulation on the java classes by

creating metadata [21]. In the second phase the persistence

process performs a schema formulation through the “schema

tool”; which generates a metadata file and use annotations to

persist the java entities. Data Nucleus Schema tool

accomplishes persistence through the “data

nucleus.autocreateSchema” property that is defined in the

persistence.XML file. The schema genera- tion process in

Data Nucleus is dependent on the”enhancer” to create

metadata for every class and sub-class in the API. In Data

Nucleus, a metadata file contains information about all the

persistable units of the API. Thus, increasing the efficiency

of the mapping process and allowing the developer to

perform abstract process by simple method calling. This

programming style is useful in distributed environment

although it is complicated in the centralized architecture.

A major distinction between the other JPA

implementations and Data Nucleus is the built-in support for

schema creation. Data Nucleus provides flexibility to

entreated schema manually, through the command prompt or

through java programming using annotations or XML files.

The entire pro-cess is highly sensitive along with the addition

of duplicate jar files. The compatibility issues in Data nucleus

could restrain the creation of metadata, in order to avoid

problems in metadata creation and managing schema a

developer usually configure the enhancements manually.

According to the data nucleus designer, a data nucleus API

must includes following jar files to complete the persistence

process i.e. datanucleus-core-2.1.1.jar, data

nucleus-enhancer- 2.1.0-release.jar, data nucleus-JPA

2.1.0-release.jar*, datanu-cleusrdbms2.1.1.jar and

asm-3.1.jar * [21] respectively. In a study by Miroslav

Nachev [21] on JPA implementations; it was stated that Data

Nucleus manages persistence process in an incremental

fashion, which mean not all fields are retrieved immediately.

The process is evolved into step as to improve the efficiency

of the overall application through the lazy loading process

called the entity graph. These graphs are further managed by

standard JPA interfaces called the EntityManagerFactory

objects and the EntityManger. All the SQL operation such as

create, delete update and select are managed by the

EntityManager.

Fig. 7. DataNucleus JPA architecture.

Fig. 7 shows a high-level DataNucleus architecture with

EntityManager objects to perform persistence. A typical JPA

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implementations persist classes defined via metadata [21].

This metadata is defined in the form of traditional XML files

or annotations. The XML files are a highly preferred mode of

object map- ping because it involves invincibly less

deployment time to retrieve and store data into the database.

Although data nucleus doesn’t define a mechanism to cache a

query [21].

III. COMPARISON OF JPA PROVIDERS

A. Connection and Configuration

Configuring a Connection in a JPA is accomplished by

setting few properties in the persistence.XML file and using

the objects of the EntityManager and the Hibernate with its

built- in and customized connection pool setup through

advanced protocols

TABLE I: CONNECTION AND CONFIGURATION FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

Connection

Pool

Build-in + Third party

Open source (c3p0,

proxool)

Not Default ,Build-in

(max/min 32 with

initial 1 connection)

Need Third party+

Plug-in support.

Not Default but third party data source

DBCP, C3P0, Proxool, Bone CP,

JNDI, and lookup connection Data

Source.

Configure

connection

Appropriately

Need to set up hibernate.

cfg.xml file with

properties.

Configure connection

Property Add-on

Connection Retry option.

Default: on-demand

Three auto start options at

classes, xml, schema table .

Detached State

Manager

Supports Transient,

Persistent and Detached

Objects in Hibernate.

Explicit Detach, cascade

Detach ,Bulk Detach

Off By Default, pros needs

enhanced persistent classes

and the OpenJPA libraries

at client tier.

Data Nucleus fetch groups to control

the specific fields to detach.

Always Close

Resources

Session need explicit

closing, Bean close

automatically.

Need to close explicitly or

will create Memory Leak

Problem.

Garbage collection+

application level cleaning.

Auto managed by Data Nucleus

Such as C3P0 [8] and protocol [8] provides the most

optimized connection. Alternatively, EclipseLink, Open-JPA,

and Data Nucleus are dependent on a third party tool.

Configuring the state of an API is a complex task. JPA

implementation such as Data nucleus’s advance functionality

fetches groups of data to control fields at the granular level.

EntityManagerFactory interfaces. According to Jorge Edison

Lascano [10], a java persistence API exfoliates adequately in

any environment, no matter whether it is an in-house intranet

that serves a few number of users or for developing a

demanding API that attends thousands of users. JPA

manages the connection implicitly through the

EntityManagerFactory which handles the bottleneck to open,

close a connection and detached or attach the allocated

resources. In the similar study, Jorge Edison Lascano [10]

also asserted that JDBC executes a cache pool in order for the

application to avoid opening connections to the database

respectively. To save time a connection pool executes the

query in data cache to implement persistence in the JPA

providers. This means that resources such as memory, cache,

and hard disk fetches the data in the persistence process as a

single persistence unit at runtime. Every JPA implementation

is assigned a set of connection protocols and fetching

strategies to optimize the resource utilization process. Table I

compares connectivity and configuration protocols and

default values in all four JPA-implementations; it deter-

mines, which JPA implementation provides the most

flexibility by customizing connection or by setting properties

and also include information about the default values that are

designated on a particular API. Other implementation i.e.

Hibernate and EclipseLink inefficiently complicate the task

by creating complex decoupling in de-allocation process [8],

[10].

B. Cache

Caching process in JPA enhances the performance of the

API during inflow and outflow of data or to execute SQL

operations on the database. According to Jorge Edison

Lascano in [10], it is stated that caching in JPA is

implemented through a series of constant updates, and the

developers do not have to bother about the refreshing the

cache or any comparable activities related to caching or

flushing. JPA manages cache through distributed cache

frameworks [10] i.e. ecache, memcached, cacheman [10] or

other JPA implementations; therefore a developer does not

have to allocate time in completing the cache services.

According to [10], caching process is divided into levels in

JPA; the first level or L1 cache is described in the persistence

context (for a session or EntityManger) while the second

level or L2 cache is called the coordinated or shared cache

[22]. To improve the performance of the cache, strategies

defined in [22] to create adjustable indexes that would

improve caching technique in JPA but the problem

nevertheless exist where the frequency of updated were high

in the API. And the third level is implemented in Data

Nucleus only in the form of a result tree [23] to generate the

query in the persistence layer. In a study by Miki Enoki et al.

caching in JPA implementation are, managed through a

flushing technique that re-initialize the internal SQL cache

and executes the command creating cache invalidation

problem. In Hibernate query cache is responsible for caching

the output of SQL queries through the primary keys [23]. In

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EclipseLink entity cache [23] require a third party assistance

to cache data. Similarly, for openJPA and data nucleus query

optimizer explicitly manages the cache when the query

executes. Table II below on Caching in JPA differentiate

between all four JPA specification by comparing various

caching features [10], [22], [23].

TABLE II: CACHING FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

Flushing

Auto by default, Other mode

Commit, manual, never,

Always

Default (off) flush

clear.cache+Drop, DropInvalide,

Merge

Automatically flush before

queries involving dirty

objects will ensure that this

never happens.

flush.mode to AUTO (default)

but allow manual handling of

"n" objects.

Data Cache(2

level)

clustered cache, JVMlevel

(SessionFactorylevel)

cache on a class-by-class

and collection- by-

collection, using any

strategy : read-write cache,

non strict-read-write,

transactional cache

Cache with no locking, no cache

refresh. -session cache(default)+

query + cache (size , .invalidation)

By default, + Eclipse Link caches

objects read from a data source

Data and Query caching

(optional cache).

-Not related to the Entity

Manager cache.

- Data cache can operate in

both single- JVM and

multi-JVM environments.

By default the Level 2 Cache

is enabled + mode of operation of

the L2 cache default

UNSPECIFIED , others include

ENABLE _ SELECTIVE ,

DISABLE _SELECTIVE, ALL,

NONE.

Utilize the

EntityManager

cache

Default 1st level cache

Add-on 2nd level and Query

cache.

Default is not shared (Entity

manager)+ shared object cache

option in EclipseLink.

RetainState configuration

option to true, using build in

cache.

Need to explicitly close

connection detachOnClose to set

to True.

Query Cache

Default Disabled, To

Turn set Property to

values=True

No Option Need to be configured

Default Disabled, To

Turn set Property to

values=True +supports

Concurrent Query Cache.

Generic Compilation Include a

tree which is database

independent.

C. Query and Transaction

According to Jorge Edison Lascano in [10] every

Transaction either retrieve or send data to the database

independent of the underlying data source. In JPA to query

entities through the java object, we use the Java Persistence

Query Language (JPQL). JPQL is a case sensitive language

queries which ex- ecute the SQL operations using the java

objects. In [10] Jorge Edison Lascano also stated, that JPA

manages large data-set optimally by reducing the SQL code

and thus avoid the SQL injections by executing the code at

runtime. Every JPA implementation follows a build-in

default fetching strategy or customized databases extraction

strategies thus eliminating the need to manage and build

fetching models. A Transaction signifies as a unit of work

performed within the relational database management system

(RDMBS) [24], following the basic relational reliable

policies called ACID property [24] (atomicity, consistency,

isolation, and durability). A JPA specification identifies

every transaction as an integral part of mapping process and

executes the queries on the entities to retrieve data from the

database. In order to understand the

Complex features in JPA implementation and compare

transactional factors to help developers understand the

functionality and perform SQL operations Table III provides

complete detailed analysis. The comparison indicates that

OpenJPA provides a wide range of options for querying

databases, but due to high bug issues in the language, other

JPA implementation such as hibernate and EclipseLink are

more preferred in terms of optimized result [10], [21], [24].

TABLE III: QUERY AND TRANSACTION FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

Transactions

Optimization

Fetch optimization techniques

and patterns. with checkpoints.

Change Tracking for

Transactions.

Aggregates and projections.

JPQL, NativeSQL +JDO Query.

Use Fetching

Lazy by default, can be set to

eager. EAGER: Convenient, but

slow. LAZY: More coding, but

much more efficient.

Lazy Default but can

make it eager.

Eager default fetch can be changed to

Lazy. Strategy could be

None, join , parallel.

JDO provides fetch groups,

whereas JPA2.1 now provides

EntityGraphs (A subset of fetch

groups).

Query Parameters

for encoding

search data in

filter Strings

Named parameters

Need help!!

PERSISTENCE_UNIT_D

EFAULT (which is

true by default)

OpenJPA Aggressive caching of

query compilation data, and the

effectiveness of this cache is

diminished if multiple query filters

are used where a single is used.

All dirty objects are

Flushed.

Large Data set

Handling

Hibernate Pagination Hibernate

ScrollableResultsNative SQL

Each has its own advantage and

disadvantage.

Pagination is one technique

used in handling data sets.

By default, OpenJPA uses

standard forward-only JDBC

result sets, and completely

instantiates the results of database

queries on execution.

Native SQL, JPQL, JDOQL

Allowing extensions for Query

handling in large data set.

Query and

Transaction

Management

Manual Transaction

Management. Can be automated

with transaction Manager.

PROPAGATION_ REQUIRED

or Use HQL.

Work in unit of work

from a session with

isolation level. To Query

use executeQuery

•Nested Unit of Work

•Parallel Unit of Work

JPQL +Extensions

Work in unit of work

With Local transactions,

JTA transactions, container

managed transactions, spring

managed transactions.

Tune fetch groups

Uses lazy select fetching for

collections and lazy proxy

fetching for single-valued.

Pre-defined fetch groups

at the Entity+ Dynamic

(use case) fetch groups at

the query level Load all

data and leave large fields

(binary, additional join)

Load all data and leave large

fields(binary, additional join)

Fetching objects with manual

control to fetch.

Database indexes

Support Indexing

@Index annotation

Manual +Build-in

IndexMetaData+ optimization

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D. Auto-Insert

Marking a field with the @GeneratedValue annotation

confines the value of the field in the relational database to

auto increment [25]. In a JPA implementation defining a

primary key to uniquely identify a row in a relation uses auto,

identity, sequence and table values. Every value specifies a

behavioral pattern, wherein an auto adds special global

number generator [25] in the ID column for every java entity.

And an incrementor called the identity which auto generate

values with an exception. The whole process is automated so

its optimal and efficient to add a primary key column into the

database. Table IV on JPA auto insert man- ages to compares

all four implementations based one major factor called

sequence increment; it depicts a comparison of the JPA

implementations based on that increment factor for auto

generation in the ID column [25].

TABLE IV: AUTO-INSERT FEATURES

JPAProviders

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

Sequence

Increment

SequenceStyleGenerator With

increment more then 1. With

following options IDENTITY

SEQUENCE (best option not

much restriction) TABLE

(SEQUENCE).

Sequence number pre-

allocation enables a batch of

ids to be queried from the

database simultaneously in

order to avoid accessing the

database for an id on every

insert. Default Value: 50.

Large bulk inserts

Sequence overhead. own

sequence factory can

further optimize sequence

number retrieval.

+Need to Set validate with

Cache property to false. +auto

identity generator is

recommended. + sequence

default can be non- optimum set

key _ cache _ size= 10.

E. JPA Object

Java Persistence API has a collection utility packages with

a wide range of embedded interfaces to create a list, set,

collection, maps, tree maps [12] and many other calculative

operations. A list and set are the most widely used utilities in

order to perform the basic data retrieval task from the object

model into the database model. Every JPA implementation

supports certain default option while retrieval of the

information from the database. Hibernate, Eclipselink, and

Data Nucleus accomplish data retrieval through Set classes.

Alternatively, OpenJPA operates on collections with an over-

head in performance while retrieving the data. While sets are

not considered an optimized solution in java method calling

because of equals and hashCode methods in entities do not

have the immutable functional key [12]. In [12] Doug Clarke

stated that a list, without an index, in hibernate and

eclipseLink is handled as a bag which degrades the

performances of the API when the load increases. Table V

shows a comparative difference among all 4 JPA

implementations based on the list and set [25] and also

differentiate which API utilize a set to execute the SQL

operations [12], [25] .

TABLE V: JPA OBJECT CLASS FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

use set instead

of List /

collections

Default used SET recommended by

Hibernate creators. But option include

List, Array, Map, bag and ibag.

Use set default

but can add JPA

class.

Default collection cause overhead, use

Set, SortedSet, HashSet, or TreeSet.

Set is default for collection

of data . can Use any other

List, Set, Array, Map.

F. Threading

A multi-threaded standalone application persists data into

the database and manages the threading issues to perform

CRUD operations (create, read, update and delete). Table VI

shows a comparison among difference JPA specification to

manage threads in the multi-database environment. Every

JPA implementation has an Entity Manager object to execute

Query and an Entity Factory Manager to handle boilerplate

code. However, Entity Manager is not threaded safe [26],

which means we cannot create an object of the Entity

Manager and perform transactions from the same instance.

Entity Factory Manager, on the other hand, is synchronized

which means that one object for EntityFactoryManager is

managed throughout the API for de-allocation and allocation

of the resources. Table VI show a comparison of all four JPA

implementation. However, it also includes a comparison

among JPA implementation based on distributed transaction

(XA) in different APIs. Many blogs, tutorial, and prior

research have discussed threading in detail and way to

improve the performance of an API but JPA manages to

achieve the accepted performance level [26].

TABLE VI: THREADING FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

Multi-threading

Do not use hibernate managed

objects in multiple threads.

Settle for ID column

Handle but

time

consuming.

Single-thread default can

be set using the

openjpa.Multithreaded

Persistence Manager

multithreaded. Default value

is false.

XAtransaction

XA(distributed

transaction)

Hibernate Transaction Manager

(searching)

Time out problem.

XA slower than standard

transaction, but support

non-xa and XA

transaction.

Nothing available.

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G. Mapping and Distributed Transactions

An Entity is an essential part of an API. In JPA

objectmodeling is performed on objects called entities. These

entities have relationships [27] defined among them.

Mapping is an association between two or more entity where

each onehas a role defined to create a relation. In an entity

cardinality of the relation defines the constraint specially to

the number of relationship. The JPA model maps a typical

java class to the relational database sordid on the subclass

and super-class relationship. In this paper, Table VII shows a

comparison of all 4 JPA implementation with several

optimization features and techniques such as; garbage

collection, pagination, batch processing, auditing and

logging to track relationships and manage the

cardinality/ordinarily of the entity to improve the mapping

process. Every implementation intuitively follows a rational

approach. But because the relation between the entities has a

bolder effect compared to the other factors it is important to

tune the entities before the intricacy occurs. However,

Hibernate support for OOPs concepts includes advanced

features to accomplish mapping efficiently relation between

the relation between the entities has a bolder-effect [28]

compared to the other factors it is important to tune the

entities before the intricacy occurs. However, Hibernate

support for OOPs concepts includes advanced features to

accomplish mapping efficiently. Whereas Open JPA and

Data nucleus inherit single table operation, compared to join

among table or a table per class strategies [27], [28].

TABLE VII: MAPPING AND DISTRIBUTED TRANSACTIONS FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

Inheritance

Hibernate supports the three basic

inheritance mapping strategies; table

per class hierarchy, table per

subclass, table per concrete class,

concrete class strategy, concrete

class using implicit polymorphism

ConcretePolymorphism doesn't

support join fetch.

Type of inheritance:

Single Table

Inheritance, Joined

Table, Table per

Concrete.

Mapping inheritance

hierarchies to a single

database table is faster for

most operations than other

Strategies employing

multiple tables. Strategy

SINGLE _TABLE,

JOINED, or TABLE _

PER_CL ASS.

Need to must specify the identity

of objects in the root persistable

class of the inheritance hierarchy.

You cannot redefine it down the

inheritance tree. Default: single _

table . Other options: Joined,

Table per class.

Composite

Persistence

Hibernate+Jboss+sprig+

JPA will work.

Composite

Persistence unit for

relational and non

relational database+

clustering.

No working 2013

Allow Run time persistence unit

using JDO or JPA use the same

persistence unit . Can't Find for

Composite.

TABLE VIII: PERFORMANCE OPTIMIZATION FEATURES

JPA Providers

Features

Hibernate

EclipseLink

OpenJPA

DataNucleus

JVM optimization

Garbage Collection

Java performance test suite.

Hotspot compilation

modes and the maximum

memory.

linked hashmap save 4%

CPU time. And Hotspot is

another option.

Preload Meta Data

Repository

Doesn't have the option

(search how it performs

the same operation in

hibernate).

MetadataSourceAdapter.

By default, the

MetaDataRepository is

lazily loaded which

means fair amounts of

locking. This option

load metadata upfront

and remove locking.

DataNucleus use JPA with

Maven in pom.xml for

Repository.

Enhancer

Bytecode enhancer(run

and compile time)

Maven, Ant , Gradle.

Weaving (run +compile time)

build-time or deploytime

enhancement. post -

compilation bytecode

enhancer.

Default enhancement before

runtime. Support Transparent

Persistence -Run +Compile

Time.

Enable

logging/Disable

Enable for performance

analysis Log4jjdbc +

jbosslogging (warn,

error and fatal).

(eclipselink.logging.level) Values

(Off, severe, warning , info,

config ,

fine, finer, finest, all) This is an

optimization feature that lets you

tune the way EclipseLink detects

changes in an Entity. Default

Value: AttributeLevel if using

weaving (Java EE default),

otherwise Deferred.

verbose logging affects

performance.

Log4J +set categories :

Persistence Transaction

Connection Query

Cache, Metadata, Data- Source,

schema native Schema-tool, JPA

IDE Value Generation

Recommended: DataNucleus

category to OFF.

Logging

Performance

Tracking/Auditing

Default Envers for

tracking old version,

individual Entity

properties (New).

ChangeTrackingType;

ATTRIBUTE, OBJECT or

DEFERRED+ Auditing

Ways. AUDIT_USER and

AUDIT_TIMESTAMP column.

Full history support.

JDBC performance

tracker(set to false).

MBeans internally to track

changes via JMX at runtime Or It

own API for Monitoring.

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H. Performance Optimization

Performance Optimization in JPA implementation

contributes some of the major criterion’s to develop an API;

it includes an optimizer, fetch strategies, indexes and

parameterized searching options [28]. To bridge different

implementations, JPA includes pre-loaded metadata

repositories. Performance Optimization in JPA

implementation contributes some of the major criterion's to

develop an API; it includes an optimizer, fetch strategies,

indexes and parameterized searching options. To bridge

different implementations, JPA includes pre-loaded metadata

repositories. These repositories are useful in order to perform

tasks, such as metadata mapping and improving query

response time. JPA implementations support pre-compiled

mapping through MetedataAdpters [28]. These adapters are

pre-loaded in the API to automate the metadata creation [28].

EclipseLink JPA includes a MetadataSourceAdapter [29] to

implement the mapping process, whereas other

implementations such as OpenJPA and Hibernate are

inefficient in loading the repositories. These repositories are

useful in order to perform tasks, such as metadata mapping

and improving query response time. JPA implementations

support pre-compiled mapping through MetedataAdpters

[30

]. Table VIII compares JPA implementations comparing

features affecting performance [28]-[30].

IV. CONCLUSION

JPA implementations acknowledge the programmers to

build extensible APIs by reducing and reusing the code to

accomplish data persistence. Furthermore, JPA also

diminishes the disk overhead and network resource

consumption because ORM maps the binding between

dissimilar modeling architectures. Moreover, applications

developed in JPA reduces the load of handling complex task

but it is not preferred in distributed databases. The high-level

abstraction, however, is seldom complex for an unfamiliar

developer. But JPA reliably manages the prospective user to

create an efficient API with a standardized interfaces. The

prospective of the paper was to consolidate the benefits and

features in the four JPA implementation i.e. Hibernate,

Eclispelink, Open-JPA and Data Nucleus. A literature review

on the JPAs would be advantageous for an unfamiliar

developer. In con- clusion, the JPA persistence providers [30]

can develop efficient API and performance oriented. But the

question resides which implementation is well suited to

which environment. This paper concretely established an

interpretation by analyzing four distinct JPA implementation

and generating a comparative summary sordid on the

specialties and etiquette of the API. Hibernate being the most

exceptional JPA standard in terms of the documentation

support and libraries to manage complicated responsibilities.

For future, an optimal solution to improve the scalability of

the API through proper documentations of the complex task

along with improving the cache mechanism in OpenJPA

[30].

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in Proc. the 2007 ACM SIGMOD International

research (NIER track),” in Proc. of the 33rd International Conference

on Software Engineering, ACM, 2011.

Neha Dhingra received the B.Sc degree in computer

and information science and the pursing second

masters in M.Sc. (Thesis) degree from University Of

Ottawa, Ottawa, Canada. She worked as a database

administrator and database developer in various IT

companies. Her research area is database and cloud

management. She has been awarded the best paper in

the Montreal conference held at University of De

Quebec Montreal, 2016. She is a certified database

administrator and developer with certifications in oracle and microsoft.

Being a certified OCA (Oracle Certified Associate) in Oracle 12 c she has

four years’ IT industry experience with hand on working expertise of

production environment. Currently, she is involved in the field Java

persistence in cloud databases.

Emad Abdelmoghith received the M.S. degree in

computer and information science and the Ph.D.

degree in information technology from Cairo

university, Cairo, Egypt in 2003 and 2008

respectively. His research interests include network

security and software engineering. He worked as

assistant professor at king Saud University, Riyadh,

KSA. He has completed his research work at

university of Ottawa, Ottawa, Canada.

Hussein Mouftah joined the School of Information

Technology and Engineering (now School of

Electrical Engineering and Computer Science) of the

University of Ottawa in 2002 as a Tier 1 Canada

research chair professor, where he became

distinguished university professor in 2006. He has

been with the ECE Dept. at Queen's University

(1979-2002), where he was prior to his departure a full

professor and the department associate head. He has

six years’ industrial experience mainly at Bell Northern Research of Ottawa

(Nortel Networks). He served as editor-in-chief of the IEEE

Communications Magazine (1995-97) and IEEE ComSoc director of

magazines (1998-99), chair of the awards committee (2002-03), director of

education (2006-07), and member of the board of governors (1997-99 and

2006-07). He has been a distinguished speaker of the IEEE communications

society (2000-2007). He is the author or coauthor of 10 books, 72 book

chapters and more than 1400 technical papers, 14 patents, 6 invention

disclosures and 144 industrial reports. He is the joint holder of 20

best/outstanding paper awards. He has received numerous prestigious

awards, such as the 2016 R.A. Fessenden Medal in telecommunications

engineering of IEEE Canada, the 2015 IEEE Ottawa section outstanding

educator award, the 2014 Engineering Institute of Canada K. Y. Lo Medal,

the 2014 technical achievement award of the IEEE Communications Society

Technical Committee on wireless Ad Hoc and sensor networks, and the

Royal Society of Canada RSC Academy of Science (2008).

International Journal of Computer Theory and Engineering, Vol. 9, No. 5, October 2017

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