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Struts & Hibernate
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| | | DAO pattern | DAO pattern 2004-11-21 - By Ananthalakshmi Subramaniyam
Back
On Thu, 18 Nov 2004 23:11:06 -0700, Darshan Kashi <dkumar@(protected)>
wrote:
>Hi,
>
> Thanks for your reply. I just gone through the link you provided, and its
>really useful for me. There is one point i need some clarification.
>
>In that article the author mentioned two approaches
>
>1. Transaction demarcation using JDBC
> (The <B>caller has no way to demarcate</B> the transaction)
>2. Transaction demarcation using JTA
> (The <B>caller is responsible for demarcating</B> the transaction)
>
>I need to control the trasaction from the caller(not in DAO), and at the
>same time i don't want to go for JTA. Is it not possible?
>
>Regards
>Darshan
>
>
>On Thu, 18 Nov 2004 09:24:35 -0300, German M. Gomez
><german_m_gomez@(protected)> wrote:
>
>>I believe you will find this link useful http://www-
>106.ibm.com/developerworks/java/library/j-dao/
>>
>>See Transaction demarcation
>>
>>
>>
>>
>>
>>
>>
>>
>>
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Unif??? en cualquier momento y
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listserv@(protected)
Hi,
Normally, it is best practice to handle Transaction demarcation outside of
DAO, in order to demarcate Transaction between multiple DAOs. This approach
is more flexible.
For example,
public class UserTransaction {
Connection conn = null;
String strUser = null;
String strDbUrl = null;
String strDbUser = null;
String strPassword = null;
public UserTransaction(String strURL, String strUser,
String strPassword) {
this.strDbUrl = strURL;
this.strDbUser = strUser;
this.strPassword = strPassword;
}
public void beginTransaction(...) {}
public void endTransaction(...) {}
public Connection getConnection() {return connection;}
public void commit() {}
public void rollback() {}
}
public class MyDAOFactory {
public static UserTransaction transaction = null;
public static final String DRIVER "COM.cloudscape.core.RmiJdbcDriver";
public static final String DBURL "jdbc:cloudscape:rmi://localhost:1099
/CoreJ2EEDB";
public static final String USER ="user";
public static final String PASSWORD = "pwd";
public static UserTransaction getUserTransaction() {
if(transaction == null ) {
UserTransaction transaction = new UserTransaction
(DRIVER,DBRUL,USER,PASSWORD);
}
return transaction;
}
...
public AccountDAO getAccountDAO();
}
public class AccountDAO {
public void credit() {
UserTransaction transaction MyDAOFactory.getUserTransaction();/use
existing user transaction or
create new one.
Connection connection = transaction.getConnection();
Statement stmt = connection.createStatement(sqlQuery);
//do the operations.
}
public void debit() {}
...
}
In Caller class,
MyDAOFactory daoFactory = new MyDAOFactory();
UserTransaction transaction = MyDAOFactory.getUserTransaction();
transaction.beginTransaction();
AccountDAO accountDAO = daoFactory.getAccountDAO();
try {
accountDAO.credit();
accountDAO.debit();
...
transaction.commit();
} catch(myDAOException ex) {
transaction.rollback();
}
transaction.endTransaction();
The above approach is helpful in both DAO demarcated Transaction and
caller demarcated transaction. ie, in DAO demarcated methods, you may have
the following implementation,
public void autonomousCredit() {
UserTransaction transaction MyDAOFactory.getUserTransaction();/use
existing user transaction or
create new one.
transaction.beginTransaction();
Connection connection = transaction.getConnection();
Statement stmt = connection.createStatement(sqlQuery);
try {
//do the operations.
transaction.commit();
} catch(Exception ex) {
transaction.rollback();
}
transaction.endTransaction();
}
Thanks,
H.Ananthalakshmi.Hi,
Normally, it is best practice to handle Transaction demarcation outside of
DAO, in order to demarcate Transaction between multiple DAOs. This approach
is more flexible.
For example,
public class UserTransaction {
Connection conn = null;
String strUser = null;
String strDbUrl = null;
String strDbUser = null;
String strPassword = null;
public UserTransaction(String strURL, String strUser,
String strPassword) {
this.strDbUrl = strURL;
this.strDbUser = strUser;
this.strPassword = strPassword;
}
public void beginTransaction(...) {}
public void endTransaction(...) {}
public Connection getConnection() {return connection;}
public void commit() {}
public void rollback() {}
}
public class MyDAOFactory {
public static UserTransaction transaction = null;
public static final String DRIVER "COM.cloudscape.core.RmiJdbcDriver";
public static final String DBURL "jdbc:cloudscape:rmi://localhost:1099
/CoreJ2EEDB";
public static final String USER ="user";
public static final String PASSWORD = "pwd";
public static UserTransaction getUserTransaction() {
if(transaction == null ) {
UserTransaction transaction = new UserTransaction
(DRIVER,DBRUL,USER,PASSWORD);
}
return transaction;
}
...
public AccountDAO getAccountDAO();
}
public class AccountDAO {
public void credit() {
UserTransaction transaction MyDAOFactory.getUserTransaction();/use
existing user transaction or
create new one.
Connection connection = transaction.getConnection();
Statement stmt = connection.createStatement(sqlQuery);
//do the operations.
}
public void debit() {}
...
}
In Caller class,
MyDAOFactory daoFactory = new MyDAOFactory();
UserTransaction transaction = MyDAOFactory.getUserTransaction();
transaction.beginTransaction();
AccountDAO accountDAO = daoFactory.getAccountDAO();
try {
accountDAO.credit();
accountDAO.debit();
...
transaction.commit();
} catch(myDAOException ex) {
transaction.rollback();
}
transaction.endTransaction();
The above approach is helpful in both DAO demarcated Transaction and
caller demarcated transaction. ie, in DAO demarcated methods, you may have
the following implementation,
public void autonomousCredit() {
UserTransaction transaction MyDAOFactory.getUserTransaction();/use
existing user transaction or
create new one.
transaction.beginTransaction();
Connection connection = transaction.getConnection();
Statement stmt = connection.createStatement(sqlQuery);
try {
//do the operations.
transaction.commit();
} catch(Exception ex) {
transaction.rollback();
}
transaction.endTransaction();
}
Thanks,
H.Ananthalakshmi.
===================================================================Companion
Site: http://www.corej2eepatterns.com
J2EE BluePrints: http://java.sun.com/blueprints/corej2eepatterns
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