Spring – Bean reference example

In Spring, beans can access to each other by specify the bean references in the same or different bean configuration file.

Bean in different XML file

<ref bean="someBean"/>

If you are referring to a bean in the different XML file, you can use the ‘ref’ tag with ‘bean’ attribute. In this example, the bean declared in ‘Spring-Common.xml’ can access any beans in ‘Spring-Output.xml’ by using a ‘ref’ attribute in property tag.

Spring-Common.xml

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 
   <bean id="OutputHelper" class="com.mkyong.output.OutputHelper">
	<property name="outputGenerator" >
		<ref bean="CsvOutputGenerator"/>
	</property>
   </bean>
 
</beans>

Spring-Output.xml

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 
<bean id="CsvOutputGenerator" class="com.mkyong.output.impl.CsvOutputGenerator" />
<bean id="JsonOutputGenerator" class="com.mkyong.output.impl.JsonOutputGenerator" />
 
</beans>

Bean in same XML file

<ref local="someBean"/>

If you are referring to a bean in the same XML file, you should use the ‘ref’ tag with ‘local’ attribute. In this example, the beans declared in ‘Spring-Common.xml’ can access to each other.

Spring-Common.xml

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 
   <bean id="OutputHelper" class="com.mkyong.output.OutputHelper">
	<property name="outputGenerator" >
		<ref local="CsvOutputGenerator"/>
	</property>
   </bean>
 
<bean id="CsvOutputGenerator" class="com.mkyong.output.impl.CsvOutputGenerator" />
<bean id="JsonOutputGenerator" class="com.mkyong.output.impl.JsonOutputGenerator" />
 
</beans>

Conclusion

Actually, the ‘ref’ can access to a bean either in same or different XML files, however, for the project readability, you should use the ‘local’ attribute if you reference to a bean which declared in the same XML file.

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