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Java Transaction API
Sean C. Sullivansean <at> seansullivan <dot> comJuly 2003
Agenda
• Java Transaction API (JTA)
• Using JTA with EJB
• Using JTA with JDBC
• Using JTA with JMS
• Using JTA with JDO
• Transactions for Web services
The J2EE platform
source: http://java.sun.com/j2ee
Definition: Transaction
“A transaction is a series of operations that appear to execute as one large, atomic operation.”
(source: Roman et al, Mastering Enterprise JavaBeans)
Definition: Transaction
“A transaction is a complete unit of work. It may comprise many computational tasks,which may include user interface, data retrieval, and communications. A typicaltransaction modifies shared resources.”
(source: The Open Group’s XA specification)
Transaction types
• Local transactions
• Distributed transactions
Local transaction
Oracle DBApplication
Distributed transaction
IBMMQSeries
Application Transactionmanager
Oracle DB
ERPsystem
J2EE transaction specifications
• Java Transaction API (JTA)
• Java Transaction Service (JTS)
JTA
“JTA is a high level, implementation independent, protocol independent API that allows applications and application servers to access transactions.”
source: http://java.sun.com/
JTS
“JTS specifies the implementation of a Transaction Manager which supports JTA and implements the Java mapping of the OMG Object Transaction Service (OTS) 1.1 specification at the level below the API. JTS propagates transactions using the Internet Inter-ORB Protocol (IIOP).”
source: http://java.sun.com/
J2EE transaction packages
JTA
• javax.transaction
• javax.transaction.xa
JTS
• javax.jts
• org.omg.CORBA
• org.omg.CosTransactions
• org.omg.CosTSPortability
JTA in action
UserTransaction utx = …;
try
{utx.begin();transferFunds(your_account,
my_swissbank_account,1000000, US_DOLLARS);
travelAgent.purchaseTicket(PDX, MEXICO_CITY);utx.commit()
}
catch (Exception ex)
{
utx.rollback();
}
Resource managers
Resourcemanager
Application Transactionmanager
Resourcemanager
Resourcemanager
Transaction terminology
• Transaction manager
• Resource manager
• Resource enlistment
• XA
• Two phase commit (2PC)
Two phase commit
Transactionmanager Resource
Manager
Prepare
Prepare
Prepare
Two phase commit (cont.)
Transactionmanager Resource
Manager
Prepared
Prepared
Prepared
Two phase commit (cont.)
Transactionmanager Resource
Manager
Commit
Commit
Commit
Two phase commit (cont.)
Transactionmanager Resource
Manager
Done
Done
Done
Transaction demarcation
• Start a transaction
• End a transaction
Techniques for transaction demarcation
• Declarative– programmer declares transaction attributes– runtime environment uses attributes to
manage transactions
• Programmatic– programmer is responsible for coding
transaction logic– application controls a transaction via an API
Package: javax.transaction
• javax.transaction.Status
• javax.transaction.Synchronization
• javax.transaction.Transaction
• javax.transaction.TransactionManager
• javax.transaction.UserTransaction
javax.transaction.UserTransaction
Methods:• public void begin()• public void commit()• public void rollback()• public void setRollbackOnly()• public void setTransactionTimeout(int)• public int getStatus()
Obtaining a UserTransaction via JNDI
import javax.transaction.*;
import javax.naming.*;
// …
InitialContext ctx = new InitialContext();
obj = ctx.lookup(
“java:/comp/UserTransaction”);
UserTransaction tx = (UserTransaction) obj;
// …
Obtaining a UserTransaction in EJB
import javax.transaction.*;
import javax.ejb.*;
// …
private EJBContext ec;
// …
utx = ec.getUserTransaction();
// …
EJB transactions
• Declarative– Container-Managed Transactions (CMT)– Transaction attributes declared in EJB
deployment descriptor (ejb-jar.xml)
• Programmatic– Bean-Managed Transactions (BMT)
Transactional EJB’s
• Session beans– either CMT or BMT
• Entity beans– always CMT
• Message driven beans– either CMT or BMT
Example: JTA and EJB
public void deposit(double amount) {
UserTransaction utx = ctx.getUserTransaction();
try {
utx.begin();
updateAccount(amount);
utx.commit();
}
catch (Exception ex) {
utx.rollback();
}
}
JTA and JDBC
If the JDBC driver implements the XADataSource interface, the database can participate as a resource manager in a JTA transaction
Using JTA and JDBC
1) Configure an XA DataSource
2) Lookup DataSource via JNDI
3) Lookup UserTransaction via JNDI
4) Invoke utx.begin()
5) Invoke DataSource.getConnection()
6) Execute SQL statements
7) Invoke utx.commit()
8) Invoke java.sql.Connection.close()
JTA and JMS
If the JMS provider supports the XAResource interface, JMS can participate as a resource manager in a JTA transaction
Example: JTA with JMS
import javax.jms.*;
import javax.transaction.*;
//
TopicSession tsess = …;
Topic top = …;
UserTransaction utx = lookupUsingJNDI();
utx.begin();
TopicPublisher publisher = tsess.createPublisher(top);
// …
Example: JTA with JMS (cont).
TextMessage msg =
tsess.createTextMessage(“Hello!”);
publisher.publish(msg);
utx.commit();
// …
Java Data Objects (JDO)
• javax.jdo.PersistenceManagerFactory
• javax.jdo.PersistenceManager– method: currentTransaction()
• javax.jdo.Transaction– method: begin()– method: commit()– method: rollback()
Example: JDO local transaction
import javax.jdo.*;
PersistenceManagerFactory pmf = …;
PersistenceManager pm = pmf.getPersistenceManager();
Transaction tx = pm.currentTransaction();
try {
tx.begin();
// ...
shirt.setColor(WHITE);
tx.commit();
}
catch (Exception ex) {
tx.rollback();
}
Example: JDO and JTA
import javax.jdo.*;
import javax.transaction.*;
UserTransaction utx = …;
try {
utx.begin();
PersistenceManager pm = pmf.getPersistenceManager();
// …
shirt.setColor(BLUE);
utx.commit();
}
catch (Exception ex) {
utx.rollback();
}
Transactions for web services
• Protocol specifications:– WS-Transaction– OASIS Business Transaction Protocol (BTP)
• Java API– JAXTX (JSR-156)
Additional topics…
• Transaction isolation levels
• Optimistic transactions
• Nested transactions
• Extended transaction models (JSR-95)
Open source projects
JBossTX– http://www.jboss.org/
JOTM– http://jotm.objectweb.org/
Tyrex– http://tyrex.sourceforge.net/
Additional resources
• http://java.sun.com/products/jta/
• http://java.sun.com/products/jts/
• http://java.sun.com/products/jdbc/
• http://java.sun.com/products/jdo/
• http://java.sun.com/products/jms/
• http://java.sun.com/products/ejb/
• http://java.sun.com/j2ee/
Summary
• If your application accesses multiple data resources, consider using JTA
• For more details, read the JTA specification
Backup slides
These additional slides are backup material.
Properties of transactions
• Atomicity
• Consistentcy
• Isolated
• Durable