Answer / prakash sah

Here is the defination and example in case of spring:

Local Vs Global Transaction:

Local transactions are transactions associated with a
particalar data source (means they are resource-specific).
the most common example would be a transaction associated
with a JDBC connection. While Global Transactions provide
the ability to work with multiple transactional resources
(typically relational databases and message queues).

Example of Local transaction :

<bean id="dataSource"
class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName"
value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>

<bean id="txManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>

DataSourceTransactionManager : takes the datasource as one
of its properties.

even HibarnateTransactionManager takes sessionfactory which
in turn uses datasource as a property or it also takes
datasource as one of the property.


Example of Global transaction :

If we use JTA in a J2EE container, as in the
'dataAccessContext-jta.xml' file from the same sample
application, we use a container DataSource, obtained via
JNDI, in conjunction with Spring's
JtaTransactionManager. The JtaTransactionManager doesn't
need to know about the DataSource, or any
other specific resources, as it will use the container's
global transaction management infrastructure.


<?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:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/jee
http://www.springframework.org/schema/jee/spring-jee-2.5.xsd">
<jee:jndi-lookup id="dataSource" jndi-name="jdbc/jpetstore"/>
<bean id="txManager"
class="org.springframework.transaction.jta.JtaTransactionManager"
/>
<!-- other <bean/> definitions here -->
</beans>

public class AboutStrings{ public static void main(String args[]){ String s1="hello"; String s2="hel"; String s3="lo"; String s4=s2+s3; //to know the hash codes of s1,s4. System.out.println(s1.hashCode()); System.out.println(s4.hashCode()); // these two s1 and s4 are having same hashcodes. if(s1==s4){ System.out.println("s1 and s4 are same."); }else System.out.println("s1 and s4 are not same."); } } Somebody told me that, == operator compares references of the objects. In the above example even though s1 and s4 are refering to same object(having same hash codes), it is printing s1 and s4 are not same. Can anybody explain in detail why it is behaving like this? Thanks in Advance RavuriVinod

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