Question

I have the following bean defined:

<bean id="myBean" class="com.me.myapp.Widget">
    <constructor-arg name="fizz" value="null"/>
    <constructor-arg name="buzz" ref="someOtherBean" />
</bean>

When I run my app, Spring throws a bean config exception:

[java] Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'myBean' defined in class path resource [spring-config.xml]:
Unsatisfied dependency expressed through constructor argument with index 0
of type [com.me.myapp.Widget]: Could not convert constructor argument value of
type [java.lang.String] to required type [com.me.myapp.Widget]: Failed to
convert value of type 'java.lang.String' to required type
'com.me.myapp.Widget'; nested exception is java.lang.IllegalStateException:
Cannot convert value of type [java.lang.String] to required
type [com.me.myapp.Widget]: no matching editors or conversion strategy found

I just want to create a Widget like I would if I wrote the following Java:

Widget w = new Widget(null, someOtherBean);

How can I do this? Thanks in advance!

Answer 1

You can use Spring’s <null> tag:

<bean id="myBean" class="com.me.myapp.Widget">
    <constructor-arg name="fizz">
            <null />
    </constructor-arg>
    <constructor-arg name="buzz" ref="someOtherBean" />
</bean>