EclipseLink/Features/JPA

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EclipseLink/Features/JPA

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1 Mapping

1.1 Basic:
DirectToFieldMapping
1.2 Relationship
Mappings
1.3 Relational
Descriptor

1.3.1 Sequencing
Policies
1.3.2 Optimistic
Locking

2 Query
Framework

2.1 Expression
Framework

2.1.1 Transactions

3 EntityManager

3.1 EntityManagerFactory
Properties
3.2 EntityManager
Properties

4 DatabasePlatform

4.1 Oracle
4.2 IBM
Platforms
4.3 Sybase
4.4 Microsoft
Platforms
4.5 Informix
4.6 Other
Database Platforms

5 ServerPlatforms
6 Performance
and Scalability Features

Mapping

Mapping entity classes to relational tables involves configuration of a mapping per persistent field.
For all mapping types there are a common
set of options available:

Read-Only: Specifies that the mapping should populate the value on read and copy. Required when multiple mappings share the same database column.

See Configuring Read-Only
Mappings in the EclipseLink User's Guide for
details.

Converters allow custom data types and data conversions to be used with most mapping types

Annotations: @Converter, @TypeConverter, @ObjectTypeConverter, @StructConverter, @Convert
XML: <converter>, <type-converter>, <object-type-converter>, <struct-converter>, <convert>

See Converters
and Transformers in the EclipseLink User's
Guide for details.

Basic: DirectToFieldMapping

Mappings where a single attribute of the entity class is mapped to a column. EclipseLink's DirectToFieldMapping is
used to represent basic mappings in the metadata model.

Direct Mapping properties

Default Value for Null

See Configuring
a Default Null Value at the Mapping Level in the EclipseLink
User's Guide for details.

Lazy
Loading (Fetch Groups)

Relationship Mappings

Relationship Mapping Features

Private-Owned: Indicates that the mapping forms a tight containment relationship. Used for cascade delete and merging operations

See Configuring
Private or Independent Relationships in the EclipseLink
User's Guide for details.

Collection Types: List, Set, Map, custom container
Transparent Indirection (Lazy Loading)

OneToOne Mapping (includes ManyToOne)

Target Foreign Key

OneToMany
ManyToMany
AggregateObject: Multiple classes within the same row

Nested aggregate object mapping

AggregateCollection
Direct Collection
Direct Map

Common Mapping Features

Converter

Custom
Object-Type
Type Conversion

Relational Descriptor

A relational descriptor allows the mapping from an entity class to one or more tables. It shares all of the capabilities of the Class
Descriptor

Single Table Mapping
Multi-table Policy:

Using primary key fields of the same name (default)
Join using a specified foreign key

Inheritance

Sequencing Policies

EclipseLink allows multiple sequences to be defined which are used to generate sequence values for new objects.

Native Sequencing

Sequence Table

Row per Sequence
Table per Sequence

Custom Sequencing Policy

Pre-allocation offers performance improvements minimizing the number of calls to the database

Optimistic Locking

A descriptor's optimistic locking policy controls how EclipseLink will use values read from the database during the writes to the row to ensure the row has not been modified by another concurrent writer.

Version

Numeric
Timestamp

Fields

All
Selected
Changed

'Note: Pessimistic locking can be configured on a query or by default on the descriptor'

Query Framework

Query Types

Object Read Queries

ReadAllQuery
ReadObjectQuery
ReportQuery: Data project query including aggregate functions and group-by support
DataReadQuery
ValueReadQuery

Object Write Queries

InsertObjectQuery
UpdateObjectQuery
WriteObjectQuery
DeleteObjectQuery

Bulk Write Queries

UpdateAllQuery
DeleteAllQuery

Expression Framework

EclipseLink's expression framework allows developers to define search criteria, ordering, batch/join reading, selective read fields, etc. using expressions based on the object model instead of coding the relational
schema into the application. This not only provides independence between the two models but also simplifies the Java developers work.
See Introduction
to EclipseLink Expressions (ELUG) in the EclipseLink User's
Guide for more information.
The query framework in conjunction with the expressions can define almost any query and can work cooperatively with EJB-QL, SQL, & Stored Procedure queries. Some of the key features include:

All comparison operators
Transparent join definition (inner & outer joins)
Pre-defined and custom inline functions (i.e. UPPER)
Sub-selects
Complex Ordering
Aggregate functions (SUM, MIN, MAX, … - ReportQuery)
GROUP BY (ReportQuery)
Re-usable expression fragments to control joining behavior
Definable batch and join reading to any level (reduces N+1 reading)

Native Queries

SQL
Stored Procedure

Query By Example
Cursored streams and Scrollable cursor

Transactions

The UnitOfWork feature is an object-level transaction to simplify development of INSERT, UPDATE, and DELETE logic.

Session Query API
Register API to include objects in TX
Thread isolated changes to object graph
Deferred writing of changes (minimal TX window possible)
Minimal change-set calculation
SQL Call Ordering determined by referential integrity rules and minimize deadlock through consistent table access.
Commit, Commit and Resume
Revert instances and all registered objects
Cache merge only on successful TX commit
PK Assignment for new objects on demand or at commit
Merge API for applying client serialized objects
Un-register instances to remove from TX
Nested & Parallel UnitOfWork support
UnitOfWork begin Early Transaction support

EntityManager

In addition to being a compliant JPA implementation EclipseLink provides advanced features through the usage of JPA's properties for customizing EntityManagerFactory and EntityManager instances.

EntityManagerFactory Properties

EclipseLink offers a number of properties for configuring an EntityManagerFactory that can be specified in either the persistence.xml or in the map passed to Persistence.createEntityManagerFactory. The configuration
of these advanced features is covered in the EclipseLink
User Guide.

JDBC
Configuration Options

JDBC Usage (Applicable to Data Source and EclipseLink's internal JDBC connection pooling)

eclipselink.jdbc.bind-parameters
eclipselink.jdbc.native-sql
eclipselink.jdbc.batch-writing

JDBC
Connection Pooling

eclipselink.jdbc.driver
eclipselink.jdbc.url
eclipselink.jdbc.user
eclipselink.jdbc.password
eclipselink.jdbc.read-connections.max
eclipselink.jdbc.read-connections.min
eclipselink.jdbc.read-connections.shared
eclipselink.jdbc.write-connections.max
eclipselink.jdbc.write-connections.min
eclipselink.jdbc.cache-statements
eclipselink.jdbc.cache-statements.size

Logging

eclipselink.logging.logger
eclipselink.logging.level
eclipselink.logging.timestamp
eclipselink.logging.thread
eclipselink.logging.session
eclipselink.logging.exceptions
eclipselink.logging.file

Caching

eclipselink.cache.type.default
eclipselink.cache.size.default
eclipselink.cache.shared.default
eclipselink.cache.type.<ENTITY>
eclipselink.cache.size.<ENTITY>
eclipselink.cache.shared.<ENTITY>
eclipselink.flush-clear.cache

Environment
Configuration and Customization

eclipselink.target-database - see Database
Platforms
eclipselink.target-server - see ServerPlatforms
Classic Metadata Usage

eclipselink.session-name
eclipselink.sessions-xml
eclipselink.session-event-listener
eclipselink.session.include.descriptor.queries

Schema
Generation

eclipselink.ddl-generation
eclipselink.application-location
eclipselink.create-ddl-jdbc-file-name
eclipselink.drop-ddl-jdbc-file-name
eclipselink.ddl-generation.output-mode

Entity
Change Tracking

eclipselink.weaving.changetracking

Weaving
Configuration

eclipselink.weaving
eclipselink.weaving.lazy
eclipselink.weaving.changetracking
eclipselink.weaving.fetchgroups
eclipselink.weaving.internal
eclipselink.weaving.eager

EntityManager Properties

Reference Mode (eclipselink.persistence.context.reference-mode) with values HARD (default), WEAK, FORCE_WEAK. Defines the reference type used to hold managed objects within a persistence context.
User defined properties: Any property passed in will be accessible from with SessionEventListener callbacks

DatabasePlatform

EclipseLink's DatabasePlatform encapsulates database specific behavior. While EclipseLink ships with out of the box and extended support for all of the leading database it is also possible to author a custom platform
or extend an existing platform to add custom behavior. The following are the capabilities defined by a database platform:

Field Types: Specifies the mapping from the common Java types to database type names. This is used for schema generation.
Native SQL (boolean, default = false): allows the user to select the usage of the default SQL92 dialect or the usage of the platform specific SQL generation.
ConversionManager
shoudTrimStrings (boolean): Indicates if strings returned form the JDBC result set should be trimed during processing
Server time query
Batch Writing configuration

Mode: Concatenation, JDBC, Native-JDBC
Batching size

Statement caching size (default = 50): controls the number of statements that will be cached per connection. this configuration is only applicable when using internal connection pooling.
Cursor handling
Transaction isolation
shouldOptimizeDataConversion (boolean, default = false): Allow for driver level data conversion optimization to be disabled, required because some drivers can loose precision.
Struct Converters: Allows converters to be set directly on the database platform. This is necessary when the Struct being converted requires the JDBC connection to complete its conversion into a Java type.

See Database
Platforms in the EclipseLink User's Guide for more information.

Oracle

OraclePlatform

Object-relational type mappings
Native Sequencing (SELECT NEXTVAL FROM DUAL)
Stored Procedure
Hints

Oracle8Platform

Hierarchical Queries
Custom LOB Support for Oracle JDBC

Oracle9Platform

Oracle Spatial

Oracle10Platform
Oracle11Platform
TimesTenPlatform

IBM Platforms

DB2

Native SQL Support (BLOB, Date, Timestamp, Time)
Custom Operators (UCASE, LCASE, CONCAT)
Server Time
Ignore no data found/modified exceptions

Mainframe DB2

Sybase

Native Sequencing (@@IDENTITY)
Native SQL (BLOB, Date, Timestamp, Time)
Stored Procedures
Server Time

Microsoft Platforms

SQL Server

Native Sequencing (@@IDENTITY)
Native SQL (BLOB, Date, Timestamp, Time)
Stored Procedures
Server Time

MS Access

Informix

Native Sequencing ("SELECT DISTINCT(DBINFO('sqlca.sqlerrd1')) FROM systables")
Native SQL (Date, Timestamp, Time)
Outer Joins

Other Database Platforms

MySQL
Derby
Cloudscape
HSQL
JavaDB
PointBase
PostgreSQL
SQLAnyWhere

ServerPlatforms

Oracle

OC4J
WebLogic Server (9, 10, 10.3)

JBoss
Tomcat 6 (EJB3 standalone)
SunAS9
IBM WebSphere (generic & 6.1)
SAP NetWeaver

Performance and Scalability Features

EclipseLink offers numerous performance tuning capabilities that allow a developer to get the optimal performance and scalability characteristics for a specific application.

EclipseLink/Features/Core#Caching
Entity Caching: Allows EclipseLink to minimize database calls and avoids unnecessary object creation

Mapping

Indirection:
Allows relationships to be lazily loaded form the database
Fetch
Groups: Allows developer to control when the attributes of a class are loaded

Query

Batch
Reading (optimized SQL generation for data retrieval)
Join
Reading (optimized SQL generation for data retrieval)
Report & Partial Attribute Queries
Stored
Procedure support
In-Memory
Querying

Transactions
(UnitOfWork)

Minimal change-sets: Only modify what has changed
Batch Writing

SQL Concatenation
JDBC batch writing
Native JDBC batching

Bulk Operations

Bulk Update: Issue a single query to update the database and invalidate cached objects effected
Bulk Delete

JDBC

Prepared
Statement Caching (when using EclipseLink's connection pooling)
Parameter
Binding (Strings, LOBs, or ALL)

Sequence
pre-allocation: Reduce quantity of database calls by retrieving PK chunks

This page was last modified 07:05, 27 May 2011 by Jon
Lee. Based on work by Sabine
Heider, Michael OBrien and Doug
Clarke and others.
This page has been accessed 49,492 times.