Data Access Layer
( “Telosys-DAL” )
Laurent Guérin / V 1.8 / 2008 – November
( for Telosys 1.0.0 and + )

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 all
the operations
Keep the SQL code and the “O/R mapping” in the Java
classes (when the code runs, it cannot be altered by
external 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 to
access a table
you don’t have to write code to create DAO and Value
Objects !
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Telosys-DAL : Overview
Application Data Access Layer
dbconfig.xml
init()
Connection
getConnection() Manager
Telosys
« SqlConnection
« DAO » Provider »
SqlConnection
AgencyVO SqlConnection
AgencyDAO Pool
AgencyVOList
SqlConnection
Pool
SqlConnection
EmployeeVO EmployeeDAO
SqlConnection
EmployeeVOList Factory SqlConnection
Value Objects J2EE Server
SQLDataSource
DataSource
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Configuration file “dbconfig.xml”
dbconfig.xml example : maxId : 0 to 100
<databases maxId="4" defaultId="0" > defaultId : 0 if not set or invalid
id : 0 to maxId
<db id = "0" poolSize :
name = "MySQL - Test DB" . 0|1 factory (no pool )
driver = "com.mysql.jdbc.Driver" .>1 pool
url = "jdbc:mysql://localhost:3306/test"
isolationLevel = "TRANSACTION_REPEATABLE_READ"
poolSize = "3" >
POOL [ 3 ]
<property name="user" value="root" />
<property name="password" value="" />
<metadata catalog="" schema="" table-name-pattern="%" table-types="TABLE VIEW" />
</db>
<db id = "1" name="DataSource MySQL" datasource="java:comp/env/jdbc/mydatasource" />
<db id = "2" Datasource (JNDI name)
name = "Oracle 10g"
driver = "oracle.jdbc.OracleDriver"
url = "jdbc:oracle:thin:@localhost:1521:XE"
isolationLevel = "TRANSACTION_READ_COMMITTED" Factory
poolSize = “0" > ( no pool )
<property name="user" value="tp" />
<property name="password" value="tp" />
<metadata catalog="" schema="TP" table-name-pattern="%" table-types="TABLE VIEW" />
</db>
</databases>
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Telosys-DAL : Initialization
Telosys-DAL stand-alone :
//--- Telosys DAL initialization with dbconfig file path
private static final String DB_CONFIG = CONF_DIR + "dbconfig.xml" ;
TelosysDAL.init(DB_CONFIG);
Telosys-DAL with Telosys framework :
Define the dbconfig file in the telosys.properties
DbConfFile = C:/Eclipse301/workspace/Telosys/conf/dbconfig.xml
DbConfFile = ./dbconfig.xml
Init Telosys framework, then Telosys-DAL
//--- 1) Telosys global initialization
Telosys.init(..., ...);
//--- 2) Telosys DAL initialization
TelosysDAL.init();
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Telosys-DAL : Connections management
ConnectionManager ConnectionProvider
<< class >> << interface >>
. init ( String dbconfigFile ) java.sql.
. getConnection()
. getDefaultDatabase() * . getName()
Connection
. getNumberOfDatabases() << interface >>
. getConnection()
. getConnection(int base)
. getSession()
. getSession(int base)
SqlDataSource
SqlConnectionProvider getConnection :
get from DataSource
javax.sql.DataSource
SqlConnection SqlConnection 1 Pool
Factory Pool ( Vector )
getConnection : getConnection :
create a new get from pool * SqlConnection
connection << class >>
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Telosys-DAL : Connections management
How to get a Connection :
//--- Connection from Default Database
Connection c1 = ConnectionManager.getConnection();
//--- Connection from Database 1
Connection c2 = ConnectionManager.getConnection(1);
How to release a Connection :
Connection c1 = ConnectionManager.getConnection();
c1.close();
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
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DAL – V.O. ( Value Objects )
The data exchange between the Data Access
Layer and the other layers is done with
“VO” ( “Value Object” ), also known
as “DTO” ( “Data Transfer Object” )
For each “VO”, 2 Java classes are required :
The VO itself
A specific list of this type of VO (with strong type
checking methods )
Example : to managed “Employees” we need …
“EmployeeVO.java” ( the VO )
“EmployeeVOList.java” ( the list of “EmployeeVO” )
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DAL – V.O. ( Value Objects )
« Employee » example :
GenericVOList Standard « DataList » provided
Telosys
. getList() by Telosys
. size()
. isEmpty()
. clear() LinkedList
extends « GenericVOList » no inheritance
EmployeeVOList EmployeeVO
Specific méthods to
encapsulate the . EmployeeVO add() . getXxxx() Value Object
generic methods of . add( EmployeeVO ) . setXxxx()
DataList . insert ( index, EmployeeVO ) . isXxxx() for entity
. replace ( index, EmployeeVO ) . toString() « Employee »
. remove ( index )
Standard template,
. remove (EmployeeVO )
but no interface
. EmployeeVO get( index ) Standard accessors,
implementation
. EmployeeVO getFirst() for each attribute
because of the strong
. EmployeeVO getNext()
type methods
List of « EmployeeVO »
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DAL – D.A.O. ( Data Access Objects )
The DAO provides methods to manipulate
A single entity : the Value Object
A list of entity corresponding to a specific Query
The Value Objects List
The DAO works with other classes :
1 Value Object ( VO )
1 Value Objects List ( VOList )
0 .. N Query (providing a VOList )
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DAL – D.A.O. ( Data Access Objects )
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 )
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DAL – D.A.O. ( Data Access Objects )
The DAO operations to manipulate SQL Queries
and V.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 )
VOList
insertList ( insert all the items of the list ) or
List
deleteList ( delete all the items of the list )
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DAL – D.A.O. ( Data Access Objects )
DAO with or without Connections ?
Each operation of a DAO has 4 signatures
Examples :
dao.save( myVO );
DB id
works with the default database ID ( cf dbconfig.xml )
dao.save( myVO, base_id );
works with the given database ID ( “int” )
dao.save( myVO, connection );
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 a
connection, useful for “Screen Managers” )
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DAL – D.A.O. ( Data Access Objects )
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 a
pool ) after each operation
The programmer never see the Connection object
With “Connection” or “DatabaseSession”
The connection management is the programmer’s
responsibility
The DAO doesn’t commit anything
And doesn’t close the connection
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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
EmployeeDAO dao = new EmployeeDAO();
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 the
files dbconfig.xml and telosys.properties )
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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()
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DAO & Entities (VO)

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 )
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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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DAO : check the existence of an entity
Set the Primary Key
vo.setId(“IdValue”);
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 doesn’t exist
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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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DAO : insert an entity
Set the VO attributes
vo.setId(“IdValue”);
vo.setOther(…);
Insert
dao.insert(vo);
SQL request :
Insert into … (…) values (…)
Return code ( int )
The standard JDBC return value (the number of rows
affected).
For an entity ( with a unique Key ) :
1 – Successful insert ( entity inserted )
else : never happen Exception
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DAO : insert with key generation
Set the VO attributes Key
vo.setAttrib1(..); attribute
is useless
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 )
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DAO : delete an entity
Set the Primary Key
vo.setId(“IdValue”);
Delete
dao.delete(vo);
SQL request :
Delete from … where …
Return code ( int )
The standard JDBC return value (the number of rows
affected).
For an entity ( with a unique Key ) :
1 – Entity deleted ( entity found and deleted )
0 – Entity not deleted ( entity not found )
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DAO : save an entity
Set the VO attributes
vo.setId(“IdValue”);
vo.setOther(…);
Save
dao.save(vo);
SQL requests :
Select count from … where …
if the enity exists
Update
else
Insert
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DAO : save an entity
Return code ( int )
The standard JDBC return value (the number of rows
affected).
For an entity ( with a unique Key ) :
Always 1 :
entity inserted 1 row affected
or
entity updated 1 row affected
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DAL – Exceptions
TelosysException try
Use a standard {
// DAO operations
“try catch” block }
catch ( TelosysException ex )
{
...
}
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…
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D.A.O. & Lists (VOList)

DAO and ListQueries
A VOList is loaded by using a DAO and a
ListQuery
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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DAO and ListQuery model
DAO ListQuery
<< interface >>
. createQuery() . setParameter(int,int)
. createQuery() creates
. setParameter(int,long)
. createQuery() . setParameter(int,short)
. createQuery() . setParameter(int,Object)
. createQueryAll() uses
. createQueryAll() . getSqlCount()
. getSqlSelect()
. getSqlDelete()
uses
Criteria
Criterion
.
.
*
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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 :
ListQuery query = dao.createQuery( "Matricule > 7000" );
ListQuery query = dao.createQuery( "Matricule > 7000" ,
"order by matricule" );
//--- Load the list using the query
dao.loadList(query, list);
Query with “ static criteria ” with parameters :
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
//--- Load the list using the query
dao.loadList(query, list);
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DAO : Query with dynamic criteria
Define the list of criteria :
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" );
At request time, choose the criteria to use :
crit.doNotUse(1);
crit.doNotUse(2);
crit.useWithValue(3, "10");
crit.useWithValue(4, "900");
Then, create the query :
ListQuery query = dao.createQuery(crit, "order by Matricule");
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DAO & ListQuery : limitations
A DAO works with only one table
DAO + ListQuery can only retrieve data from a
single table ( a list of VO/records load form the
table )
To retrieve data with complexes requests…
see “DataSet”
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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 there’s no risk of integrity violation when
using a global “delete” for a list
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DAO : List persistence
Bulk insert/update/delete :
dao.insertList(list)
dao.updateList(list)
dao.deleteList(list)
Insert, update or delete all the elements of the
given list ( VOList or standard java.util.List )
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D.A.O. & Sequences

Sequence DAO
A “Sequence DAO” is a specific type of DAO
dedicated to the SEQUENCES
It provides the standard “NEXT VAL”
and “CURR VAL” operations
Sequence DAO are available for …
Oracle
PostgreSQL
MySQL ( sequence simulation with tables )
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Sequence DAO
How to create and use a “Sequence DAO” …
SequenceDAO seq = new SequenceDAO( "request_id_seq", SequenceDAO.POSTGRESQL);
//--- With the default DataBase SequenceDAO.POSTGRESQL
long val = seq.nextVal(); SequenceDAO.ORACLE
SequenceDAO.MYSQL
//--- With a specific DataBase ID
long val = seq.nextVal(DbId);
//--- With a connection
long val = seq.nextVal(c);
long val = seq.currVal(c); NB :
//--- With a DB Session
currVal only with
long val = seq.nextVal(s); a connection
long val = seq.currVal(s);
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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 DAO
EmpIdSeqDAO empIdSeq = new EmpIdSeqDAO();
System.out.println("nextVal : " + empIdSeq.nextVal() );
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DataSet

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 TABLE
with ROWS and COLUMNS
A “DataSet” is “abstract” and its content can be
loaded from different sources.
The “source” of the DataSet is defined in a
“DataSet definition”
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DataSet
Principle
Step 1 : “define it” ( constructor + definition )
DataSet ds = new XXXXXX(…);
Step 2 : “load or reload it”
ds.load() Origin types for SQLDataSet :
- Connection
ds.load ( origin ) - DatabaseSession
- Integer ( Database Id )
Step 3 : “use it”
ds.load();
for ( int i = 1 ; i <= ds.getRowCount() ; i++ )
{
DataRow dr = ds.getDataRow(i);
System.out.println(" ROW = [" + dr.toString() + "] ");
String s = dr.getString(1));
Date d = dr.getDate(3));
int i = dr.getInt(4));
}
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DataSet : how to fetch data
for ( int i = 1 ; i <= ds.getRowCount() ; i++ ) From 1 to MAX
{
DataRow dr = ds.getDataRow(i);
System.out.println(" dr.toString() = [" + dr.toString() + "] ");
String s = dr.getString(1));
Date d = dr.getDate(3));
int i = dr.getInt(4));
}
Iterator iter = ds.iterator();
while ( iter.hasNext() )
{
DataRow dr = (DataRow)iter.next();
System.out.println(" dr = [" + dr + "] ");
}
Object o = ds.getObject(2,3); // ( Row, Col ) Row : 1 to MAX
String s = ds.getString(2,3); // ( Row, Col ) Col : 1 to MAX
float f = ds.getFloat(2,3); // ( Row, Col )
if ( ds.isEmpty() )
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DataSet : how to sort rows
Once the DataSet is loaded, it can be sorted by
column
ds.sort ( 2 ) ; Sort column 2
ds.sort ( 2, "ASC" ) ; Sort column 2 in ascending order
ds.sort ( 2, "DESC" ) ; Sort column 2 in descending order
ds.sortIgnoreCase ( 2 ) ;
ds.sortIgnoreCase ( 2, "ASC" ) ;
ds.sortIgnoreCase ( 2, "DESC" ) ;
if ( ds.isSorted ( 2 ) )
if ( ds.isSortedInAscendingOrder() )
if ( ds.isSortedInDescendingOrder() )
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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 of SQLDataSetDefinition
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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" , No parameter in criteria :
null , no "where clause"
"order by name" ); or static "where clause"
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
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SQLDataSet and relational DB
Use case 2 :
SQLDataSet with parameters ( static criteria )
//--- DataSet with one INTEGER parameter
int [] paramTypes = { ParamType.INTEGER } ; // One param ( INTEGER )
SQLDataSetDefinition def = new SQLDataSetDefinition(
"select name, manager, agency",
"from employee",
1 .. N fixed parameters
"where agency = ? ",
in the "where clause"
"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
String paramValues[] = { "1" }; // Array of param value(s)
//--- Create the DataSet with the Definition
SQLDataSet ds = new SQLDataSet( def, paramValues );
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SQLDataSet and relational DB
Use case 3 : SQLDataSet with “dynamic criteria”
SQLDataSetDefinition def = new SQLDataSetDefinition(
"select name, manager, agency",
"from employee",
null, No "where clause" ( dynamic )
"order by name"); If "where clause", dynamic criteria will be added
//--- 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 criteria
crit.useWithValue(1, "ZO%");
crit.doNotUse(2);
crit.doNotUse(3);
crit.useWithValue(4, "7000");
//--- Create the DataSet with the Definition
SQLDataSet ds = new SQLDataSet( def, crit );
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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 “Dynamic
Criteria”
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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 are
retrieved 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();
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THE END