Spring bean reference example

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

1. Bean in different XML files

If you are referring to a bean in different XML file, you can reference it with a ‘ref‘ tag, ‘bean‘ attribute.

    <ref bean="someBean"/>

In this example, the bean “OutputHelper” declared in ‘Spring-Common.xml‘ can access to other beans in ‘Spring-Output.xml‘ – “CsvOutputGenerator” or “JsonOutputGenerator“, by using a ‘ref’ attribute in property tag.

File : 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>

File : 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>

2. Bean in same XML file

If you are referring to a bean in same XML file, you can reference it with ‘ref‘ tag, ‘local‘ attribute.

    <ref local="someBean"/>

In this example, the bean “OutputHelper” declared in ‘Spring-Common.xml‘ can access to each other “CsvOutputGenerator” or “JsonOutputGenerator“.

File : 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’ tag 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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