Understand regarding REQUIRED and REQUIRES_NEW

[Ashwin Sridhar]

Hi,

I understood that when Transaction attribute is REQUIRED, the transaction continues in the existing Transaction and if its REQUIRES_NEW, the transaction starts in a new transaction suspendin the existing transaction.

But I don't find any concrete evidence for the same.

Below is the code snippet i tried

 @Transactional(propagation = Propagation.REQUIRED)
public void myMethod(){
		System.out.println("This "+jdbcTemplate);
		transactionTemplate.execute(new TransactionCallbackWithoutResult() {
			
			@Override
			protected void doInTransactionWithoutResult(TransactionStatus arg0) {
				// TODO Auto-generated method stub
				try{jdbcTemplate.execute("insert into testtable values('FIRST','VALUE',1)");
				myMethod2();
				System.out.println("Insertde");
				//throw new Exception();
				}catch(Exception e){
					arg0.setRollbackOnly();
					System.out.println("Rolled back");
				}
			}
		});
	}
	@Transactional(propagation = Propagation.REQUIRES_NEW)
	public void myMethod2(){
		System.out.println("Inside ano tra");
		transactionTemplate.execute(new TransactionCallbackWithoutResult() {
			
			@Override
			protected void doInTransactionWithoutResult(TransactionStatus arg0) {
				try{	jdbcTemplate.execute("insert into testtable2 values('Second','Value',2)");
				System.out.println("inserted second value");
				//throw new Exception();
				}catch(Exception e){
					arg0.setRollbackOnly();
					System.out.println("Rolled back inner");
				}
			}
		});
 

I expected following things, but never happened

1. When inner method completes successfully and exception is thrown in outer method, I expected the inner table will not be rolledback as it is in a new transaction. But both tables were rolled back.

2. When inner table throws error, data from inner table is rolledback but not sure why data fro outer table is also rolled back.

All this behaviour seems to be following ACID, but what is the difference between REQUIRED and REQUIRES_NEW. Ideally both seems to be doing something.

Could someone clarify this

[Saifuddin Merchant]

How are you running this code? (whats your main like)?

For @Transactional annotation to work you need have a TransactionProxy (created automatically) when you use <tx:annotation-driven>
However spring proxies don't work in nested call scenario's - if a method of the class calls another method in the same class the proxy gets by-passed.

Provide your spring config & your main, if you need more info ...

[Ashwin Sridhar]

Hi,

Please find below my config and java files.

package Inter;

import org.springframework.jdbc.core.JdbcTemplate;


import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.transaction.support.TransactionCallback;
import org.springframework.transaction.support.TransactionCallbackWithoutResult;
import org.springframework.transaction.support.TransactionTemplate;




public class TestClass {


	String name= null;
	int age ;
	JdbcTemplate jdbcTemplate ;
	TransactionTemplate transactionTemplate;
	
	public TransactionTemplate getTransactionTemplate() {
		return transactionTemplate;
	}
	public void setTransactionTemplate(TransactionTemplate transactionTemplate) {
		this.transactionTemplate = transactionTemplate;
	}
	public TestClass() {
		// TODO Auto-generated constructor stub
	}
	public JdbcTemplate getJdbcTemplate() {
		return jdbcTemplate;
	}

	public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
		this.jdbcTemplate = jdbcTemplate;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		System.out.println("called");
		age = 100;
		this.name = name;
	}
	
	@Transactional(propagation = Propagation.REQUIRED,rollbackFor = Exception.class)
	public void myMethod(){
		System.out.println("This "+jdbcTemplate);
		transactionTemplate.execute(new TransactionCallbackWithoutResult() {
			
			@Override
			protected void doInTransactionWithoutResult(TransactionStatus arg0) {
				// TODO Auto-generated method stub
				try{jdbcTemplate.execute("insert into testtable values('FIRST','VALUE',1)");
				myMethod2();
				System.out.println("Insertde");
				//throw new Exception();
				}catch(Exception e){
					arg0.setRollbackOnly();
					System.out.println("Rolled back");
				}
			}
		});
	}
	@Transactional(propagation = Propagation.REQUIRES_NEW)
	public void myMethod2(){
		System.out.println("Inside ano tra");
		transactionTemplate.execute(new TransactionCallbackWithoutResult() {
			
			@Override
			protected void doInTransactionWithoutResult(TransactionStatus arg0) {
				try{	jdbcTemplate.execute("insert into testtable2 values('Second','Value',2)");
				System.out.println("inserted second value");
				throw new Exception();
				}catch(Exception e){
					arg0.setRollbackOnly();
					System.out.println("Rolled back inner");
				}
			}
		});
	}
	
}

config file is

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
                        http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                        http://www.springframework.org/schema/tx 
                        http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">
                        
   <bean id="myClass" class="Inter.TestClass" >
   		<property name="name" value="ash"/>
   		<property name="jdbcTemplate" ref="jdbcTemplate"/>
   		<property name="transactionTemplate" ref="transactionTemplate"></property>
   </bean>                     
    
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
    	<property name="dataSource" ref="myDataSource"></property>
    </bean>            
    
    <bean id="myDataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
		<property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"/>
		<property name="url" value="URL"/>
		<property name="username" value="USER"/>
		<property name="password" value="PASSWORD"/> 
    </bean>  
    
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    	<property name="dataSource" ref="myDataSource"></property>
    </bean>      
    
    <bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
    	<property name="transactionManager" ref="transactionManager"></property>
    </bean>
	<tx:annotation-driven/>

</beans>

[Saifuddin Merchant]

yep your code looks good - but where is the main? how do you run this code?

To try out transaction - here is a suggestion. Put myMethod2() in a different class say Test2. Do you now notice any difference in the transaction working between Propagation.REQUIRED and Propagation.REQUIRES_NEW

[Ashwin Sridhar]

I really don't find any appreciable difference between the two. Atleast am not able to notice.

In main i just get the context and call the method. I use applicationContext to do this.

[Ashwin Sridhar]

Hi,

When i had the second method within another class, the inner transaction gets committed and outer transaction rolls back when i throw a exception in outer transaction.

Could you ellaborate this behaviour

[Saifuddin Merchant]

The answer depends on what you already know.

Do you know how Spring works when you add a @Transactional annotation?
Ans: It does so by creating a proxy class for the class which has annotated methods.

Do you know how Spring Proxy object works when one method in the proxied class calls another method in the same proxied class?
Ans: Sprig is not able to handle this scenario implicitly. Any annotation on the called method would be ignored (since the call happens on 'this' rather than on the Proxy)
You need to switch to AspectJ to handle such scenario's

If you really like to understand this behavior I recommend reading this section of the Spring documentation.

[Ashwin Sridhar]

thank you very much