Telosys DAL v1.8

8/8/2019 Telosys DAL v1.8

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Telosys 1

Data Access Layer

( Telosys-DAL )

Laurent Gurin / V 1.8 / 2008 November

( for Telosys 1.0.0 and + )

Telosys framework - D.A.L. ( Laurent Gurin / ver 1.8 ) 2

Telosys-DAL : The big principles

Telosys-DAL goals : Provide an easy way to write and use standard CRUD

DAOs ( for single Value Objects and Lists )

Let the programmer see the SQL code and control allthe operations

Keep the SQL code and the O/R mapping in the Javaclasses (when the code runs, it cannot be altered byexternal files)

Increase the productivity by providing a set of classes to encapsulate all the JDBC complexity

external tools to generate the specific Java code required toaccess a table

you dont have to write code to create DAO and ValueObjects !


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Telosys 2


Telosys-DAL : Overview

Data Access Layer

Value Objects

ConnectionManager

SqlConnection

SqlConnection

SqlConnection

SqlConnectionPool

SqlConnectionPool

SqlConnectionFactory

SqlConnectionProvider

AgencyVO

EmployeeVO

EmployeeVOList

DAO

AgencyDAO

EmployeeDAO

Application

init()

getConnection()

AgencyVOList

SQLDataSourceDataSource

Telosys

J2EE Server

dbconfig.xml


Configuration file dbconfig.xml

dbconfig.xml example :


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Telosys 3


Telosys-DAL : Initialization

Telosys-DAL stand-alone :

Telosys-DAL with Telosys framework : Define the dbconfig file in the telosys.properties

Init Telosys framework, then Telosys-DAL

//--- Telosys DAL initialization with dbconfig file path

private static final String DB_CONFIG = CONF_DIR + "dbconfig.xml" ;

TelosysDAL.init(DB_CONFIG);

//--- 1) Telosys global initialization

Telosys.init(..., ...);

//--- 2) Telosys DAL initialization

TelosysDAL.init();

DbConfFile = C:/Eclipse301/workspace/Telosys/conf/dbconfig.xml

DbConfFile = ./dbconfig.xml


Telosys-DAL : Connections management

SqlConnectionProvider

. getConnection()

. getName()

ConnectionProvider>

*

. init ( String dbconfigFile )

. getDefaultDatabase()

. getNumberOfDatabases()

. getConnection()

. getConnection(int base)

. getSession()

. getSession(int base)

ConnectionManager>

SqlConnectionFactory

SqlConnectionPool

SqlDataSource

javax.sql.DataSource

SqlConnection>

java.sql.Connection

>

Pool( Vector )

getConnection :create a newconnection

getConnection :get from pool

getConnection :get from DataSource

*

1


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Telosys 4


Telosys-DAL : Connections management

How to get a Connection :

How to release a Connection :

if the connection comes from

a pool

it is recycled ( in the Telosys pool ) a factory it is closed

a datasource managed by the DataSource

//--- Connection fromDefault Database

Connection c1 = ConnectionManager.getConnection();

//--- Connection fromDatabase 1

Connection c2 = ConnectionManager.getConnection(1);

Connection c1 = ConnectionManager.getConnection();

c1.close();


DAL V.O. ( Value Objects )

The data exchange between the Data AccessLayer and the other layers is done withVO ( Value Object ), also knownas DTO ( Data Transfer Object )

For each VO, 2 Java classes are required :

TheVO itself A specific list of this type of VO (with strong type

checkingmethods )

Example : to managed Employees we need EmployeeVO.java ( the VO )

EmployeeVOList.java ( the list of EmployeeVO )


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Telosys 5


DAL V.O. ( Value Objects )

. getXxxx()

. setXxxx(). isXxxx()

. toString()

EmployeeVO

. EmployeeVO add()

. add( EmployeeVO ). insert ( index, EmployeeVO )

. replace ( index, EmployeeVO )

. remove ( index )

. remove (EmployeeVO )

. EmployeeVO get( index )

. EmployeeVO getFirst()

. EmployeeVO getNext()

EmployeeVOList

. getList()

. size()

. isEmpty()

. clear()

GenericVOList

LinkedList

List of EmployeeVO

Value Object

for entity Employee

Employee example :

no inheritance

Standard DataList providedby Telosys

extends GenericVOList

Specific mthods toencapsulate the

generic methods ofDataList

Standard template,but no interfaceimplementationbecause of the strongtype methods

Standard accessors,for each attribute

T

e

los

y

s


DAL D.A.O. ( Data Access Objects )

The DAO provides methods to manipulate A single entity : theValue Object

A list of entity corresponding to a specific Query TheValue Objects List

The DAO works with other classes :

1 Value Object ( VO ) 1 Value Objects List ( VOList )

0 .. N Query (providing aVOList )


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The DAO operations to manipulate a single V.O.

load (try to load a VO using its primary key)

save (save a VO by SQL insert or update )

delete (delete a VO using its primary key )

insert ( try to insert the VO )

insertKeyGen ( insert with key generation )

update ( try to update the VO )

exists ( check if the VO exists in the database )



The DAO operations to manipulate SQL QueriesandV.O. lists createQuery ( create a SQL query to be used afterwards )

loadList ( load a list as the result of a Query )

saveList ( save a list by a SQL delete using the Query criteria& n SQL insert for all the items of the list)

deleteList ( delete the list using the Query criteria )

count ( do a select count(*) .. using the Query criteria )

List elements management ( without Query ) : updateList ( update all the items of the list )

insertList ( insert all the items of the list )

deleteList ( delete all the items of the list )

VOListor

List


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DAO with or without Connections ?Each operation of a DAO has 4 signaturesExamples :

dao.save( myVO );works with the default database ID ( cfdbconfig.xml )

dao.save( myVO, base_id );works with the given database ID ( int )

dao.save( myVO, connection );

works with the given standard JDBC Connection dao.save( myVO, database_session );

works with the given DatabaseSession object( a DatabaseSession is a Telosys object which encapsulate aconnection, useful for Screen Managers )

DB

id

Connectio

n



With logical DB id ( without Connection ) The DAO uses the ConnectionManager

to get a connection ( ConnectionManager.getConnection(); )

Each insert, update or delete is commited automatically

The connection is closed (recycled if it belongs to apool ) after each operation

The programmer never see the Connection object

With Connection or DatabaseSession The connection management is the programmers

responsibility

The DAO doesnt commit anything

And doesnt close the connection


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Telosys 8

How to use D.A.O.


How to get a DAO instance

A DAO is thread-safe=> its instance can be shared an reused

1/ Using the default DAO constructor

2/ Using a DAO provider if any (since v 1.0.0)Employee bean = new Employee();

DAOProvider provider = TelosysDAL.getDAOProvider();

EmployeeDAO dao ;

dao = (EmployeeDAO)provider.getDAO(bean); // by bean instance

dao = (EmployeeDAO)provider.getDAO(bean,3); // same but for DB 3

dao = (EmployeeDAO)provider.getDAO(Employee.class); // by bean class

dao = (EmployeeDAO)provider.getDAO(Employee.class,3); // same for DB 3

( the dynamic DAO registries can be defined in thefiles dbconfig.xml and telosys.properties )

EmployeeDAO dao = new EmployeeDAO();


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Telosys 9


DAO management

DAO description : String s = dao.describe()

The returned string contains the DAO Java Class

the DAO target TABLE

the set of SQL requests for standard operations :SELECT, INSERT, UPDATE, DELETE

Other methods String dao.getTableName()

Class dao.getEntityBeanClass()

SqlRequests dao.getSqlRequests()

DAO & Entities (VO)


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DAO : load an entity by PK

Set the Primary Key vo.setId(IdValue);

Try to load the entity dao.load(vo);

SQL request : Select from where

Return code ( int) : 1 Found and loaded ( VO attributes are populated )

0 Not found ( no change on the VO )


DAO : load with lock

Lock the record with a SELECT FOR UPDATE : dao.load(vo,FOR UPDATE);

NB: Database specific => any string can be used !

Use string constants !


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Telosys 11


DAO : check the existence of an entity


Check existence if ( dao.exists(vo) )

boolean b = dao.exists(vo)

SQL request : Select count where

Return code ( boolean) True : the entity exists

False : the entity doesnt exist


DAO : update an entity

Set the VO attributes vo.setId(IdValue);

vo.setOther();

Update dao.update(vo);

SQL request : Update table set where

Return code ( int) The standard JDBC return value (the number of rows

affected). For an entity ( with a unique Key ) : 1 Entity updated ( entity found and updated )

0 Entity not updated ( entity not found )


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Telosys 12


DAO : insert an entity


vo.setOther();

Insert dao.insert(vo);

SQL request : Insert into () values ()


affected). For an entity ( with a unique Key ) : 1 Successful insert ( entity inserted )

else : never happen Exception


DAO : insert with key generation

Set the VO attributes vo.setAttrib1(..);

vo.setAttrib2(..);

Insert Long key = dao.insertKeyGen(vo);

Set the Key attribute in the VO instance vo.setId( key.intValue() );

SQL request : Insert into () values ()

Return code : The generated key wrapped in a Long object

( or null if none )

Keyattributeis useless


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Telosys 13


DAO : delete an entity


Delete dao.delete(vo);

SQL request : Delete from where


affected). For an entity ( with a unique Key ) : 1 Entity deleted ( entity found and deleted )

0 Entity not deleted ( entity not found )


DAO : save an entity


vo.setOther();

Save dao.save(vo);

SQL requests : Selectcount from where

if the enity exists

Update

else

Insert


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Telosys 14


DAO : save an entity


affected). For an entity ( with a unique Key ) : Always 1 :

entity inserted 1 row affected

or

entity updated 1 row affected


DAL Exceptions

TelosysException Use a standardtry catch block

What can happen ? Duplicate key on insert

Other standard JDBC exceptions : the table has changed => the DAO is not up to date

an integrity rule is violated

etc

try

{

// DAO operations

}

catch ( TelosysException ex )

{

...

}


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Telosys 15

D.A.O. & Lists (VOList)


DAO and ListQueries

A VOList is loaded by using a DAO and aListQuery

A ListQuery holds 3 SQL requests with the same WHERE clause :

Select from WHERE

Select count form WHERE Delete form WHERE

The parameters to set in the WHERE clause

Lifecycle : 1/ created by the DAO

2/ customized with the specific parameters

3/ passed to the DAO methods to managed VOLists


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Telosys 16


DAO and ListQuery model

. setParameter(int,int)

. setParameter(int,long)

. setParameter(int,short)

. setParameter(int,Object)

. getSqlCount()

. getSqlSelect()

. getSqlDelete()

ListQuery>

. createQuery()

. createQuery()

. createQuery()

. createQuery()

. createQueryAll()

. createQueryAll()

DAO

creates

uses

.

Criteria

.

Criterion

*

uses


DAO : Query for all the entities of a table

How to load ALL the entities of a table//--- Create the DAO

EmployeDAO dao = new EmployeDAO();

//--- Create the VOList

EmployeVOList list = new EmployeVOList();

//--- Define a query

ListQuery query = dao.createQueryAll(); // ALL (no WHERE clause)

//--- Load the list using the query

dao.loadList(query, list);

//--- Print the list size

System.out.println("List size = " + list.size());

//--- Print all the VO of the list

Iterator iter = list.iterator() ;

int i = 0 ;

while ( iter.hasNext() )

{

System.out.println(" . " + (i++) + " : " + iter.next() );

}

ListQuery query = dao.createQueryAll( order by name );


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DAO : Query with static criteria

Query with static criteria without parameters :

Query with static criteria with parameters :

ListQuery query = dao.createQuery( "Matricule > 7000" );

ListQuery query = dao.createQuery( "Matricule > 7000" ,

"order by matricule" );



ListQuery query = dao.createQuery( "Matricule > ? and Matricule < ? " );

ListQuery query = dao.createQuery( "Matricule > ? and Matricule < ? ",

"order by matricule" );

query.setParameter( 1, 100 ); // First parameter value

query.setParameter( 2, 200 ); // Second parameter value



Param. index :from 1 to N


DAO : Query with dynamic criteria

Define the list of criteria :

At request time, choose the criteria to use :

Then, create the query :

Criterion [] SQL_CRITERIA =

{

new Criterion( "nom like ?" , ParamType.STRING ), /* 1 */

new Criterion( "prenom like ?" , ParamType.STRING ), /* 2 */

new Criterion( "Matricule > ?" , ParamType.INTEGER ), /* 3 */

new Criterion( "Matricule < ?" , ParamType.INTEGER ) /* 4 */

};

Criteria crit = new Criteria (SQL_CRITERIA, "and" );

crit.doNotUse(1);

crit.doNotUse(2);

crit.useWithValue(3, "10");


ListQuery query = dao.createQuery(crit, "order by Matricule");


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Telosys 18


DAO & ListQuery : limitations

A DAO works with only one table

DAO + ListQuery can only retrieve data from asingle table ( a list of VO/records load form thetable )

To retrieve data with complexes requests see DataSet


DAO : List persistence

The DAO supports global list persistence,based on a query criteria :

dao.deleteList( query ) Delete all the occurrences corresponding to the query

criteria

dao.saveList( query, list) Save the new list content by removing all the existing

items then inserting the new list items : Delete all the occurrences corresponding to the query criteria

Insert all the occurrences of the list parameter

NB : be sure that theres no risk of integrity violation when

using a global delete for a list


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Telosys 19


DAO : List persistence

Bulk insert/update/delete :

dao.insertList(list)

dao.updateList(list)

dao.deleteList(list)

Insert, update or delete all the elements of thegiven list ( VOList or standard java.util.List )

D.A.O. & Sequences


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Sequence DAO

A Sequence DAO is a specific type of DAOdedicated to the SEQUENCES

It provides the standard NEXT VALand CURR VAL operations

Sequence DAO are available for Oracle

PostgreSQL

MySQL ( sequence simulation with tables )


Sequence DAO

How to create and use a Sequence DAO

SequenceDAO seq = new SequenceDAO( "request_id_seq", SequenceDAO.POSTGRESQL);

//--- With the default DataBase

long val = seq.nextVal();

//--- With a specific DataBase ID

long val = seq.nextVal(DbId);

//--- With a connection

long val = seq.nextVal(c);

long val = seq.currVal(c);

//--- With a DB Session

long val = seq.nextVal(s);

long val = seq.currVal(s);

NB :currVal only witha connection

SequenceDAO.POSTGRESQLSequenceDAO.ORACLESequenceDAO.MYSQL


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Sequence DAO

Best practice : create a class for each sequence

public class EmpIdSeqDAO extends SequenceDAO

{

public EmpIdSeqDAO()

{

super( "EmpId" , ORACLE);

}

}

//--- Use an existing Sequence DAOEmpIdSeqDAO empIdSeq = new EmpIdSeqDAO();

System.out.println("nextVal : " + empIdSeq.nextVal() );

DataSet


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DataSet

A DataSet is a set of DataRow ( 0..N rows )

A DataRow is a set of Object ( 0..N cells )

=> a DataSet is like a TABLEwith ROWSand COLUMNS

A DataSet is abstract and its content can beloaded from different sources.

The source of the DataSet is defined in aDataSet definition


DataSet

Principle

Step 1 : define it ( constructor + definition ) DataSet ds = new XXXXXX();

Step 2 : load or reload it ds.load()

ds.load ( origin )

Step 3 : use it

ds.load();

for ( int i = 1 ; i


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DataSet : how to fetch data

for ( int i = 1 ; i


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SQLDataSet


SQLDataSet

A SQLDataSet is an extension (subclass)of "DataSet"

It can be loaded from a relational database,using a definition based on a SQL request

The definition for a SQLDataSet is held by an

instance ofSQLDataSetDefinition


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SQLDataSet and relational DB

Use case 1 : Basic SQLDataSet (no parameter)//--- DataSet without SQL parameters

SQLDataSetDefinition def = new SQLDataSetDefinition(

"select name, manager, agency",

"from employee" ,

null ,

"order by name" );

SQLDataSetDefinition def2 = new SQLDataSetDefinition(

"select name, manager, agency from employee where agency > 10" );

//--- Set a specific Database ID

def.setDatabaseId(2);

//--- Create the DataSet with the definition

SQLDataSet ds = new SQLDataSet( def );

//--- Load the DataSet using the Database specified in the definition

ds.load() ;

//--- Examples with the load(Object)method :

ds.load(new Integer(1)); // load using the given Database ID

ds.load(connection); // load using the given JDBC Connection

ds.load(dbSession); // load using the given DatabaseSession

No parameter in criteria :no "where clause"or static "where clause"



Use case 2 :SQLDataSet with parameters ( static criteria )//--- DataSet with one INTEGER parameter

int []paramTypes = { ParamType.INTEGER } ; // One param ( INTEGER )



"from employee",

"where agency = ? ","order by name",

paramTypes ); // Array of param types

SQLDataSetDefinition def2 = new SQLDataSetDefinition(

"select name, manager, agency from employee where agency > ?",

paramTypes );

//--- Set the parameter values

StringparamValues[] = { "1" }; // Array of param value(s)

//--- Create the DataSet with the Definition

SQLDataSet ds = new SQLDataSet( def,paramValues );

1 .. N fixed parametersin the "where clause"


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Use case 3 : SQLDataSet with dynamic criteria



"from employee",

null,

"order by name");

//--- Define the dynamic criteria

Criterion[] SQL_CRITERIA = {

new Criterion("name like ?", ParamType.STRING), /* 1 */

new Criterion("manager like ?", ParamType.STRING), /* 2 */

new Criterion("agency > ?", ParamType.INTEGER), /* 3 */

new Criterion("agency < ?", ParamType.INTEGER) /* 4 */

};

Criteria crit = new Criteria(SQL_CRITERIA, "and");

//--- Set dynamically the useful criteriacrit.useWithValue(1, "ZO%");

crit.doNotUse(2);

crit.doNotUse(3);


//--- Create the DataSet with the Definition

SQLDataSet ds = new SQLDataSet( def, crit );

No "where clause" ( dynamic )If "where clause", dynamic criteria will be added


SQLDataSet use cases

DataSet are useful for

Complex SQL request :the SQLDataSetDefinition support Joins between different tables

Additional SQL clauses :

Order by Group by

Search services :complex criteria combination with DynamicCriteria


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Other SQLDataSet capabilities

Use the SQLDataSet definition for "count" int n = ds.count() ;

Execute a "select count(*)" with the dataset definition criteria

Load a "page" (a subset of the request result) Define the number of lines per page :

def.setLinesPerPage(100); // default = 20

Load a page : ds.loadPage(2);

The SQL request is executed, only the expected rows areretrieved from the JDBC ResultSet

boolean b = ds.endOfResultSet();To know if the last row of the ResultSet has been loaded

Retrieve the SQL request : String sql = ds.getSqlRequest();

T H E E N D

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Telosys DAL v1.8

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