Page History

Anchor
Overview Overview

Overview

Service Data Object (SDO) and Service Component Architecture (SCA) are the basic building blocks in Service Oriented Architecture (SOA). SDO is the way of representing data in SCA. As the applications using SOA have back-end data representation in different formats like Database, File System, XML Based Data, etc., there is a need to provide a mapping between these data representations and SDO. Java RDB DAS (Data Access Service for Relational Database) is the effort to suffice this mapping requirement for Relational Database. There is a C++ implementation coming up too.

Anchor
Function Description Function Description

Function Description

RDB DAS provides 2 major capabilities:-
1) Execute SQL Queries and return result as a graph of Data Objects.
2) Reflect changes made to a graph of Data Objects back to the database.
It also supports explicit CUD SQL statements execution against database.
Image Added

Anchor
Architecture Architecture

Architecture

This section describes the overall architecture of Java RDB DAS. The details are elaborated in Design Details. Also, for details of different DAS Configuration settings, refer to Configuration Schema(config.xsd).

DAS functions based on external Configuration. This configuration can be specified using file or can be programmatically build by the caller, using ConfigHelper interface.

Design follows a factory pattern to create DAS instance. DAS instance contains Connection, Config and Commands.

The Connection can either be passed from caller or can be created using the Configuration information. It is used for all the database operations done in that DAS instance and also for controlling transactions. Configuration parameter managedtx decides whether the transaction will be controlled by DAS or by caller.

Commands hold all the commands from Configuration file and also the ones that are created programmatically on the fly. The Command is implemented using different inherited classes like Read/Insert/Update/Delete/StoredProcedure/OptimisticWrite

with

root

parent

class

CommandImpl

.

More

details

on

different

classes

will

be

in

Design

Details

.

Config

holds

the

reference

for

Configuration

associated

with

the

DAS

instance

and

contains

all

details

as

mentioned

in

Configuration

Schema

(config.xsd)

.

Caller has 2 (and some other) main APIs available in DAS instance to use the Commands getCommand(name)

and

applyChanges(Data

Object)

1. getCommand(name)

1. is

1. typically

1. used

1. to

1. retrieve

1. the

1. Command

1. (SQL

1. String)

1. available

1. from

1. Config.

1. SQL

1. String,

1. Connection

1. and

1. Parameters

1. required

1. for

1. the

1. SQL

1. are

1. contained

1. in

1. the

1. Command

1. instance.

1. User

1. also

1. needs

1. to

1. call

1. setParameter()

1. on

1. Command

1. as

1. required

1. by

1. the

1. underlying

1. SQL.

1. User

1. finally

1. calls

1. execute()

1. /executeQuery()

1. on

1. this

1. Command

1. and

1. based

1. on

1. whether

1. it

1. is

1. CUD/Read

1. operation.

1. executeQuery()

1. returns

1. DataObject.

2. applyChanges(Data

1. Object)

1. is

1. the

1. way

1. to

1. process

1. a

1. SDO

1. DataObject

1. and

1. SDO

1. ChangeSummary

1. to

1. create

1. SQL

1. UPDATE

1. statement

1. to

1. be

1. executed

1. against

1. database.

1. More

1. details

1. on

1. SDO

1. integration

1. are

1. in

1. Design

1. Details

1. .

Anchor
User Interface User Interface

User Interface

DAS exposes a set of interfaces to end user. Javadoc is available for all public APIs at https://svn.apache.org/repos/asf/incubator/tuscany/java/javadoc

.

• DASFactory Different options to produce DAS instance using Factory pattern.
  Method Summary

  DAS	createDAS(java.sql.Connection

• connection)

• Creates

• a

• DAS

• based

• on

• the

• provided

• connection

• DAS

• createDAS(java.io.InputStream

• configStream)

• Creates

• a

• DAS

• based

• on

• the

• provided

• config

• file

• stream

• DAS

• createDAS(java.io.InputStream

• configStream,

• java.sql.Connection

• connection)

• Creates

• a

• DAS

• based

• on

• the

• provide

• config

• file

• stream

• and

• connection

• DAS Interface to call APIs for DAS instance.
  Field Summary

  static DASFactory

  FACTORY

  Method Summary

  void	applyChanges(DataObject root)	The change history is scanned and modifications to the graph of data objects are flushed to the database.
  Command	createCommand(java.lang.String sql)	Creates a Command based on the provided SQL statement
  Command	getCommand(java.lang.String name)	Gets the named command from this factory's inventory
  void	releaseResources()	If the CommandGroup is managing connections then this method must be called when the client is done with the instance.

• Command Used to execute read / write (CRUD) on database.
  Method Summary

  void	execute()	Performs the function defined by the command
  DataObject	executeQuery()	Performs the function defined by the command and return the results in the root DataObject
  int	getGeneratedKey()	Returns the value of the database-generated key.
  java.lang.Object	getParameter(int index)	Returns the value of the associated Parameter
  void	setParameter(int index, java.lang.Object value)	Sets the value of the associated Parameter

• ConfigHelper It is used as an aid in programmatic construction of Config instances. This is an
  alternative to providing needed configuration information in an XML file.
  Constructor Summary

  ConfigHelper()

  ConfigHelper(Config config)

  Method Summary

  Column	addColumn(Table table, java.lang.String columnName, java.lang.String propertyName)
  void	addConnectionInfo(java.lang.String dataSourceName)
  void	addConnectionInfo(java.lang.String dataSourceName, boolean managedtx)
  void	addConnectionInfo(java.lang.String driverClass, java.lang.String databaseURL, java.lang.String user, java.lang.String password, int loginTimeout)
  void	addCreateStatement(Table table, java.lang.String statement, java.lang.String parameters)
  Command	addDeleteCommand(java.lang.String name, java.lang.String sql)
  void	addDeleteStatement(Table table, java.lang.String statement, java.lang.String parameters)
  Command	addInsertCommand(java.lang.String name, java.lang.String sql)
  void	addPrimaryKey(java.lang.String columnName)
  Relationship	addRelationship(java.lang.String parentName, java.lang.String childName)
  Relationship	addRelationship(java.util.Vector parentNames, java.util.Vector childNames)
  Command	addSelectCommand(java.lang.String name, java.lang.String sql)
  Table	addTable(java.lang.String name, java.lang.String typeName)
  Command	addUpdateCommand(java.lang.String name, java.lang.String sql)
  void	addUpdateStatement(Table table, java.lang.String statement, java.lang.String parameters)
  Config	getConfig()
  void	setDataObjectModel(java.lang.String dataObjectModel)

• Converter A lightweight Table-column <--> DataObject-property converter framework. Converters allow a user to insert a transformation between a column's value and its destination DataObject property's value. For example, by default, a VARCHAR column will be represented as a String in its corresponding DataObject property. A user could insert a converter that transforms the VARCHAR value to an Integer. If this is done then although the column returns character data, the DataObject property will be an Integer
  Method Summary

  java.lang.Object	getColumnValue(java.lang.Object propertyData)	Transform the columnData object to a new value and possibly new type
  java.lang.Object	getPropertyValue(java.lang.Object columnData)	Transform the columnData object to a new value and possibly new type.

• Pager An iterator-like interface to conveniently move through chunks of data. The idea is that a Pager works with a read Command. The read command returns a large amount of data and the client wants to work with chunks of it at a time. So the Pager is created on the command and each call to next returns the next chunk of data.
  Method Summary

  DataObject	getPage(int page)	Return a specific identified page
  DataObject	next()	Get the next page of data
  DataObject	previous()	Get the page prior to the last page returned

• GraphMerger is utility class implementation (no interface), to provide functions for flexibly managing DataObjects.
  Constructor Summary

  GraphMerger()

  Method Summary

  void	addPrimaryKey(java.lang.String key)
  DataObject	emptyGraph(Config config)
  DataObject	merge(DataObject primary, DataObject secondary)
  DataObject	merge(java.util.List graphs)

Anchor
Class Diagram Class Diagram

Class Diagram

Image Added

Anchor
Design Details Design Details

Design Details

Major classes are described here at high level to show how these fit in the complete picture. For methods/members details please refer to https://svn.apache.org/repos/asf/incubator/tuscany/java/javadoc

.

DASFactoryImpl

Expose

methods

to

create

DAS

instance

from

Config

or

Connection

or

both.

DASImpl

The

sole

instance

of

DAS

existing

for

one

DAS

runtime.

It

contains

MappingWrapper,

JDBC

Connection

and

a

Map

of

all

DAS

Commands.

To

create

appropriate

instances

of

CommandImpl,

DASImpl,

scan's

each

Config

Command

for

attribute

kind,

and

based

on

that

required

instance

of

CommandImpl

is

added

to

the

map.

Connection

from

DataSource

or

Database

Driver

Manager

both

are

supported.

releaseResources()

method

allows

external

caller

to

close

JDBC

Connection

when

it

is

supplied

by

the

caller.Provides

methods

to

get/create

DAS

Commands

and

applyChanges(changed

DataObject)

to

reflect

DataObject

changes

to

Database.

MappingWrapper

Wrapper

over

DAS

Config.

Provides

various

get/set

methods

for

all

different

elements

in

DAS

Config.

ConnectionImpl

Contains

JDBC

Connection,

and

whether

it

is

managed

by

DAS/caller

and

also

whether

Database

platform

support

auto-generated

key

column

values.

BaseCommandImpl

Parent

class

for

all

other

CommandImpl

classes.

Contains

MappingWrapper.

setConnection()

method

to

associate

ConnectionImpl

with

each

DAS

Command.

ApplyChangesCommandImpl Extends BaseCommandImpl.

Contains

ChangeSummarizer.

It

is

used

to

load

DataObject's

ChangeSummary

and

for

each

change,

Generator

classes

(UpdateGenerator,

DeleteGenerator)

are

called

to

form

appropriate

SQL

Statement

with

parameters,

which

is

executed

against

the

Database.

CommandImpl Extends BaseCommandImpl and implements DAS Config's

<Command>.

So,

in

effect

it

is

parent

class

for

all

explicit

CRUD

Commands.

It

contains

Statement,

Parameters

and

ResultSetShape.

WriteCommandImpl Extends CommandImpl.

Parent

for

CUD.

If

SELECT(Read)

is

attempted,

exception

is

thrown.

DeleteCommandImpl

Extends

WriteCommandImpl.

InsertCommandImpl Extends WriteCommandImpl.

Supports

Database

generated

keys.

UpdateCommandImpl

Extends

WriteCommandImpl.

OptimisticWriteCommandImpl

Extends

UpdateCommandImpl.

Supports

OCC

feature.

Here

by

design

when

a

CollisionParameter's

value

is

attempted

to

change

more

than

once,

the

CollisionParameter

does

not

allow

its

value

change

(as

during

first

setValue(),

flag

indicating

that

value

is

changed

is

set).

So,

the

attempt

results

in

no

database

rows

getting

changes.

On

this

condition

exception

is

thrown

as

Update

Collision

is

occurred.

ReadCommandImpl Extends CommandImpl.

Used

for

explicit

SELECT.

Support's

DAS

feature,

ResultDescriptor.

If

CUD

is

attempted,

exception

is

thrown.

Supports

paging.

When

Query

is

executed

(executeQuery()),

the

JDBC

ResultSet

is

converted

into

DataObject

Graph

and

returned

to

caller.

SPCommandImpl Extends ReadCommandImpl for StoredProcedure call. Method executeQuery()

is

used

when

the

stored

procedure

returns

ResultSet

and

method

execute()

is

used

when

the

stored

procedure

does

not

have

any

return

ResultSet.

Parameters

hold

both

IN

and

OUT

parameters.

PagerImpl

Holds

ReadCommandImpl,

page

size

and

current

page

index.

Implements

next(),

previous(),

getPage(index)

methods.

In

each

based

on

current

page

index

and

page

size,

the

ReadCommandImpl

is

executed

with

start

and

end

boundaries

set.

ChangeFactory This class is used during DAS.applyChanges().

With

changed

DataObject

and

ChangeSummary,

required

type

of

ChangeOperation

instance

is

created

(like

DeleteOperation,

UpdateOperation).

This

instance

of

ChangeOperation

holds

appropriate

CommandImpl,

which

in

itself

holds

the

Parameters.

Thus

for

a

given

DAS

Config

and

Connection,

ChangeFactory

is

used

to

propagate

DataObject

changes

to

Database

via

CommandImpl.

ChangeSummarizer

Main

function

of

this

class

is

load

Changes

based

on

root

DataObject

of

applyChanges()

Command

MappingWrapper

is

used

to

sort

the

ChangeOperations

in

Changes.

Changes

Contains

DeleteList,

InsertList,

Update

List

pertaining

to

one

applyChanges()

command.

DeleteList

Maintains

ordered/unordered

list

of

DeleteOperations.

If

DAS

Config

defines

any

Relationships,

MappingWrapper

aids

in

forming

Delete

Order

for

all

the

Tables

undergoing

DeleteOperation,

based

on

Parent-Child

relationships.

If

Delete

Order

is

available,

DeleteList

forms

a

List

following

appropriate

Referential

Integrity.

Otherwise

no

order

is

maintained.

InsertList

Maintains

ordered/unordered

list

of

CreateOperations.

If

DAS

Config

defines

any

Relationships,

MappingWrapper

aids

in

forming

Insert

Order

for

all

the

Tables

undergoing

InsertOperation,

based

on

Parent-Child

relationships.

If

Insert

Order

is

available,

InsertList

forms

a

List

following

appropriate

Referential

Integrity.

Otherwise

no

order

is

maintained.

UpdateList

As

UpdateOperation

happens

on

single

Table,

there

is

no

reason

for

sorting

based

on

any

Referntial

Relationships.

So,

this

class

is

just

a

wrapper

on

ArrayList.

BaseGenerator

Parent

class

for

Delete/Update/InsertGenerator.

If

in

DAS

Config,

any

Table

Column

specifies

a

ColumnConverter

class,

BaseGenerator,

returns

a

new

instance

of

this

class.

DeleteGenerator

Extends

BaseGenerator.

Based

on

Table

and

DAS

Config,

DELETE

statement

is

generated

with

Primary

Keys

in

WHERE

clause.

Using

this,

DeleteCommandImpl

is

instantiated.

For

Parameters

in

DeleteCommandImpl

ColumnConverter

is

considered

if

present.

InsertGenerator

Same

as

DeleteGenerator.

Here

Database

Key

value

generation

is

also

considered.

UpdateGenerator

Extends

BaseGenerator.

In

UPDATE

statement

WHERE

clause

Primary

Keys

are

considered

as

well

as

Default

OCC

policy

is

considered.

Also

check

is

implemented

for

any

violation

for

Foreign

Key

relationships.

Parameters

in

UpdateCommandImpl

consider

ColumnConvert

as

appropriate.

OCC

attributes

in

DAS

Config

for

<Column>,

viz.

managed

and

collision

are

considered

in

SET

and

WHERE

clause

formation

respectively.

ChangeOperation

Abstract

parent

class

for

Create/Delete/UpdateOperation.

It

contains

WriteCommand,

DatabaseObject

and

any

generated

ID.

DeleteOperation Extends ChangeOperation.

Uses

SDO's

ChangeSummary

based

OldValues

as

in

the

DataGraph

,

deleted

objects

have

lost

their

settings

.

CreateOperation

Extends

ChangeOperation,

makes

use

of

Generated

ID.

UpdateOperation

Extends

ChangeOperation

and

makes

use

of

generated

ID.

DatabaseObject

Wraps

DataObject.

If

a

field

is

FK,

it

will

return

value

from

parent.

It

also

sets

the

Database

generated

value

in

primary

key

property

of

DataObject.

RowObjects

Holds

a

Map

of

TableName->DataObject.

It

uses

relationship

information

to

associate

these

DataObjects

to

form

DataGraph

.

GraphBuilderMetadata

Class

that

form

Metadata

for

forming

DataObjects

based

on

MetaData

available

in

JDBC

ResultSet.

It

uses

DAS

Config,

ResultSet

and

ResultSetShape

to

form

a

Collection

of

ResultMetaData.

It

is

used

in

ResultSetProcessor

and

thus

further

in

RowObjects.

ResultSetProcessor

This

class

is

used

to

transform

data

in

ResultSet

into

set

of

inter-related

DataObjects.

It

contains

TableRegistry,

GraphBuilderMetadata

and

DataObjectMaker.

Using

GrapbBuilderMetadata

and

the

JDBC

ResultSet,

it

forms

ResultSetRow

,

then

form

RowObjects

and

connects

related

DataObjects

using

Relationship

information

from

RowObjects

to

form

the

completed

DataGraph.

DataObjectMaker

Forms

DataObject

based

on

TableData.

It

is

used

in

ResultSetProcessor

for

this.

TableRegistry

Base

Interface

for

Single/MultiTableRegistry.

SingleTableRegistry No functionality.

MultiTableRegistry Implements TableRegistry. Used when converting JDBC ResultSet of SQL SELECT into DataObjects.

DefaultConverter Implements Converter. In case of Blob database column type, returns byte[] for the column value when mapping from database data to property value.

ResultMetaData Holds complete ResultSet related metadata of the Query result- ResultSet, ColumnConverters, MappingWrapper, SDO Type Names, SDO Property Names, ResultSetShape for the ResultSet, Map containing Table Type > Column Property (equivalent to Database Table>Column). It provides various get methods on these members.

ResultSetRow A ResultSetRow is used to transform a single row of ResultSet into a set of DataObjects. It uses TableData as a intermediate place to keep Database Data for a Row , which is later used to form DataObject. It holds a List of all Table Data for the current row. This class is used in ResultSetProcessor.

TableData Holds single JDBC row for a Table and its Columns - tableName, list of PKs, Map of ColumnName->Data, if table has PK. Is used by DataObjectMaker to form DataObject based on Table Row.

ResultSetTypeMap Provides mapping from sql.Types to SDO Type. Used in ResultSetShape to populate SDO Type[] for all columns present in ResultSet.

FactoryRegistry Maintains registry of ChangeFactory. There is one FactoryRegistry for on DAS Config and Connection. It maintains a Map with entries of each SDO Type against ChangeFactory for current DAS Config+Connection.

ParameterImpl Holds values required for representing SQL statement/StoredProcedure parameter like name, index, value, SDO Type and columnConverter. Can have direction IN/OUT/IN-OUT.

IN

is

default.

OUT/IN-OUT

is

only

in

case

of

Stored

Procedure.

ManagedParameterImpl Extends ParameterImpl.

Expected

to

be

integer

or

BigDecimal

type,

else

exception

is

thrown.

setValue()

returns

oldValue+1.

CollisionParameter

Extends

ParameterImpl.

Design

restricts

setting

value

in

CollisionParameter

only

once.

Parameters Maintains lists of parameters (used in SQL statements),

IN/OUT

parameters

(used

in

stored

procedures).

ResultSetShape

This

is

an

alternative

to

use

ResultSetMetaData

of

the

Query

result.

It

can

be

used

when

some

platforms

like

Oracle

do

not

fully

support

MetaData.

For

a

given

SQL

Query,

this

holds

schemaName,

tableName,

columnName,

SDO

Column

Type

for

each

column

in

ResultSet.

It

has

2

constructors,

one

uses

JDBC's

ResultSetMetaData

to

form

ResultSetShape

and

another

uses

DAS

Config

supplied

ResultDescriptor

to

form

ResultSetShape.

Statement

Holds

SQL

String,

JDBC

connection,

JDBC

PreparedStatement

and

also

state

information

whether

the

current

statement

is

used

by

Pager.

SDODataTypeHelper

Provides

mapping

between

SDO's

Type

and

JDBC's

sql.Types.

SDODataTypes

Uses

SDO's

TypeHelper

to

get

SDO

Type

for

given

string.

QualifiedColumn Maintains schemaName,

tableName

and

columnName

for

a

Table's

Column.

RelationshipWrapper

Wrapper

for

DAS

Config's

<Relationship>.

Only

one

method

to

return

Collection

of

all

FKColumns

in

a

Relationship.

TableWrapper

Wrapper

on

DAS

Config's

<Table>.

Provides

various

get

methods

to

get

values

of

different

elements

and

attributes

within

<Table>.

ConfigUtil

Uses

SDO's

XMLHelper

to

load

DAS

Config

Data

Model

in

memory.

DataObjectUtil

Provides

utility

methods

for

SDO

DataObject

like

copying

one

DataObject

into

another,

restoring

Old

Values

of

a

DataObject

using

its

SDO's

ChangeSummary.

Anchor
Configuration Schema(config.xsd) Configuration Schema(config.xsd)

Configuration

Schema(config.xsd)

Complete

DAS

Configuration

follows.

Convention

No Format
_+Element_+ {attribute}<attribute> [_Child Element] {noformat} _Config_-> {uri} Not used {dataObjectModel} Needs a valid value when creating static DataObjects. {databaseSchemaNameSupported} when true, multiple database schema under same database are supported [Command]_

Config->
<uri> Not used
<dataObjectModel> Needs a valid value when creating static DataObjects.
<databaseSchemaNameSupported> when true, multiple database schema under
same database are supported
Command-0..n

[

Table

]

-0..n

[

Relationship

]

-0..n

[

ConnectionInfo

]

-0..1

_

ConnectionInfo

_

->

{dataSource}complete URL of data source {managedtx}if true, DAS manages database transaction [ConnectionProperties]

<dataSource>complete URL of data source
<managedtx>if true, DAS manages database transaction
ConnectionProperties-0..1

_

ConnectionProperties

_

->

{driverClass}complete qualified class name {databaseURL}database URL {username} authentic database user {password} password for the user {loginTimeout}in milliseconds _Command_-> {name} {SQL kind}Select

<driverClass>complete qualified class name
<databaseURL>database URL
<username> authentic database user
<password> password for the user
<loginTimeout>in milliseconds

Command->
<name>
<SQL kind>Select/Update/Delete/Insert/procedure

[

Parameter

]

-0..n

[

ResultDescriptor

]

-0..n

_

Parameter

_

->

{columnName} database table column name (no meaning when Command kind is procedure) {direction}IN/OUT (OUT makes sense when Command kind is "procedure") {index}used in

<columnName> database table column name (no meaning when Command kind is
procedure)
<direction>IN/OUT (OUT makes sense when Command kind is "procedure")
<index>used in set/getParameter()

on

Command

based

on

direction

(used

when

Command

kind

is

procedure).

_

ResultDescriptor

_

->

Used

as

alternative

to

database

result

set

metadata.

{columnName} database table column name {tableName} database table name {schemaName} used when databaseSchemaNameSupported=true {columnType}SDO mapped data type _Relationship_-> {name} {primaryKeyTable} {foreignKeyTable} {many} =true allows for 1:n relationship. If it is false, it's 1:1 relationship. {keyRestricted} In case of 1:1 relationship, if keyRestricted is not specified, the link (relationship) between the parent and child rows can be broken, by setting the parentKeyTable's row to null/deleting the row. Also, a different parent row can be associated to the child row, which has one pre-existing parent row association. If keyRestricted=true, this kind on change in existing relationship is not allowed, user will get exception 'Can not modify a one to one relationship that is key restricted'. [KeyPair]-0..n _KeyPair_-> {PrimaryKeyColumn}database table column name {ForeignKeyColumn}database table column name _Table_-> {tableName}Database table name {typeName}Data Object type name {schemaName} used when databaseSchemaNameSupported=true [Column]-0..n [Create]-0..1 [Update]-0..1 [Delete]-0..1 _Create_-> {sql} INSERT statement in PreparedStement format {parameters}space separated column names used in explicit INSERT _Update_-> {sql} UPDATE statement in PreparedStement format {parameters} space separated column names used in explicit UPDATE _Delete_-> {sql} DELETE statement in PreparedStement format {parameters} space separated column names used in explicit DELETE _Column_-> {columnName} database table column name {propertyName} SDO data object's property name {converterClassName} if converter is used, this needs a valid class name {primaryKey}true if column is PK {generated} true if column value is database generated {collision} when true, during UPDATE statement generation, that column is included in the WHERE clause.(OCC feature) {managed} when true, during UPDATE statement generation, that column (needs to be BigDecimal) value is incremented by 1 and used in the SET clause in UPDATE. managed=true, is effective only when collision=true, else managed attribute value is ignored. {noformat} h3. {anchor:Scalability Aspects} Scalability Aspects Java RDB DAS has exposed [User Interface|#User Interface] for end user. Other than that, from design perspective, many major DAS classes do not have associated interfaces and by design are tightly coupled with SDO and Database. It needs further enhancement on this line, especially when more DAS flavors are coming up as mentioned in [Future|#Future]. As DAS is a bridge between SOA based applications and backend Data Sources, the interfaces with SOA and Data Source need to be flexible. E.g. SDO/Some Other mechanism should be pluggable when using DAS as well as different technologies based Data Sources can be supported like XML files, LDAP based file system and so forth. Work is in-progress on this front. h3. {anchor:Future} Future DAS is implemented in Java and C++ and both are integrated with SDO and support Relational Database based Data Source. There are other flavors of DAS coming up like LDAP DAS, XQuery DAS etc. These implementations will provide different ways to interface with the backend data source as their names suggest. h3. {anchor:Samples} Samples There are a couple of samples distributed to demonstrate working examples of using different DAS features. See User Guide/Samples for more details. h3. {anchor:Terminology and Useful Links} Terminology and Useful Links | 1 | User Guide | [|

<columnName> database table column name
<tableName> database table name
<schemaName> used when databaseSchemaNameSupported=true
<columnType>SDO mapped data type

Relationship->
<name>
<primaryKeyTable>
<foreignKeyTable>
<many> =true allows for 1:n relationship. If it is false, it's 1:1 relationship.
<keyRestricted> In case of 1:1 relationship, if keyRestricted is not specified, the
link (relationship) between the parent and child rows can be broken, by setting the
parentKeyTable's row to null/deleting the row. Also, a different parent row can
be associated to the child row, which has one pre-existing parent row association.
If keyRestricted=true, this kind on change in existing relationship is not allowed,
user will get exception 'Can not modify a one to one relationship that is key
restricted'.
KeyPair-0..n

KeyPair->
<PrimaryKeyColumn>database table column name
<ForeignKeyColumn>database table column name

Table->
<tableName>Database table name
<typeName>Data Object type name
<schemaName> used when databaseSchemaNameSupported=true
Column-0..n
Create-0..1
Update-0..1
Delete-0..1

Create->
<sql> INSERT statement in PreparedStement format
<parameters>space separated column names used in explicit INSERT

Update->
<sql> UPDATE statement in PreparedStement format
<parameters> space separated column names used in explicit UPDATE

Delete->
<sql> DELETE statement in PreparedStement format
<parameters> space separated column names used in explicit DELETE

Column->
<columnName> database table column name
<propertyName> SDO data object's property name
<converterClassName> if converter is used, this needs a valid class name
<primaryKey>true if column is PK
<generated> true if column value is database generated
<collision> when true, during UPDATE statement generation, that column is
included in the WHERE clause.(OCC feature)
<managed> when true, during UPDATE statement generation, that column (needs
to be BigDecimal) value is incremented by 1 and used in the SET clause in
UPDATE.
managed=true, is effective only when collision=true, else managed attribute value
is ignored.

Anchor
Scalability Aspects Scalability Aspects

Scalability Aspects

Java RDB DAS has exposed User Interface for end user. Other than that, from design perspective, many major DAS classes do not have associated interfaces and by design are tightly coupled with SDO and Database. It needs further enhancement on this line, especially when more DAS flavors are coming up as mentioned in Future. As DAS is a bridge between SOA based applications and backend Data Sources, the interfaces with SOA and Data Source need to be flexible. E.g. SDO/Some Other mechanism should be pluggable when using DAS as well as different technologies based Data Sources can be supported like XML files, LDAP based file system and so forth. Work is in-progress on this front.

Anchor
Future Future

Future

DAS is implemented in Java and C++ and both are integrated with SDO and support Relational Database based Data Source. There are other flavors of DAS coming up like LDAP DAS, XQuery DAS etc. These implementations will provide different ways to interface with the backend data source as their names suggest.

Anchor
Samples Samples

Samples

There are a couple of samples distributed to demonstrate working examples of using different DAS features. See User Guide/Samples for more details.

Anchor
Terminology and Useful Links Terminology and Useful Links

Terminology and Useful Links