How do I wire / inject a null value in Spring?

By Wayan in Spring Core 0 Comment

To wire or inject a null value into a bean we can use the <null> element. The configuration below show you how to do it in the Spring configuration file. You might need to wire a null value for instance when you want to override a value that was autowired into a bean.

As you can see on the configuration below we set the value of property writer in the bean song to a null And we also set a couple null values into the songs property in the album bean.

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">

    <bean id="song" class="org.kodejava.spring.core.Song">
        <property name="title" value="I Saw Her Standing There" />
        <property name="writer">
            <null />
        </property>
    </bean>

    <bean id="album" class="org.kodejava.spring.core.Album">
        <property name="title" value="Please Please Me" />
        <property name="year" value="1963" />
        <property name="songs">
            <list>
                <ref bean="song" />
                <null />
                <null />
            </list>
        </property>
    </bean>

</beans>
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