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

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-3.0.xsd">

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

    <bean id="album" class="org.kodejava.example.spring.collections.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>

Wayan Saryada

Programmer, runner, recreational diver, live in the island of Bali, Indonesia. Mostly programming in Java, creating web based application with Spring Framework, Hibernate / JPA.

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