Spring Autowire Fundamentals - spring

Question

I am a newbie in Spring and am trying to understand the below concept.
Assume that accountDAO is a dependency of AccountService.
Scenario 1:
<bean id="accServiceRef" class="com.service.AccountService">
<property name="accountDAO " ref="accDAORef"/>
</bean>
<bean id="accDAORef" class="com.dao.AccountDAO"/>
Scenario 2:
<bean id="accServiceRef" class="com.service.AccountService" autowire="byName"/>
<bean id="accDAORef" class="com.dao.AccountDAO"/>
In AccountService Class:
public class AccountService {
AccountDAO accountDAO;
....
....
}
In the second scenario, How is the dependency injected ? When we say it is autowired by Name , how exactly is it being done. Which name is matched while injecing the dependency?
Thanks in advance!

Answer 1

Use #Component and #Autowire, it's the Spring 3.0 way
#Component
public class AccountService {
#Autowired
private AccountDAO accountDAO;
/* ... */
}
Put a component scan in your app context rather than declare the beans directly.
<?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:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:component-scan base-package="com"/>
</beans>

Answer 2

<bean id="accServiceRef" class="com.service.accountService" autowire="byName">
</bean>
<bean id="accDAORef" class="com.dao.accountDAO">
</bean>
and
public class AccountService {
AccountDAO accountDAO;
/* more stuff */
}
When spring finds the autowire property inside accServiceRef bean, it will scan the instance variables inside the AccountService class for a matching name. If any of the instance variable name matches the bean name in the xml file, that bean will be injected into the AccountService class. In this case, a match is found for accountDAO.
Hope it makes sense.