How to properly override beans with Spring in Maven Projects with multiple modules based on runtime profiles?

Question

So let's say I have a bean in application-context.xml :

<bean id="foo" class="biz.tugay.FooImpl" />

and I have another module, let's say module thud and in application-context-thud.xml I will also have:

<bean id="foo" class="biz.tugay.thud.ThudFooImpl" />

So when I run my application with profile thud activated, bean foo will be overriden with biz.tugay.thud.FooImpl . Up to this point all is ok.

But lets say all I want is something like this:

package biz.tugay

class FooImpl{
    void foo(){// Lots of code here};
}

and in the overriden bean all I want to do is:

package biz.tugay.thud

class ThudFooImpl{
    void foo(){
        if(something..) return;
        else {
            // Lots of code here
        }
    };
}

so what I currently do is this:

package biz.tugay.thud

import biz.tugay.FooImpl

class ThudFooImpl extends FooImpl{
    void foo(){
        if(something..) return;
        else {
            super.foo();
        }
    };
}

But the problem is, if FooImpl has dependencies, I will have to inject the dependencies to the ThudFooImpl as well. But as you can see from the code, I do not even need those dependencies in ThudFooImpl .. All I have is a simple if check.

So code will look like this in the xml files:

 <bean id="foo" class="biz.tugay.Foo">
    <constructor-arg ref="waldo"/>
    <property name="baz" ref="baz"/>
    <property name="qux" ref="qux"/>
    <property name="quux" ref="quux"/>
    <property name="corge" ref="corge"/>
</bean>

<bean id="foo" class="biz.tugay.thud.ThudFooImpl">
    <constructor-arg ref="waldo"/>
    <property name="baz" ref="baz"/>
    <property name="qux" ref="qux"/>
    <property name="quux" ref="quux"/>
    <property name="corge" ref="corge"/>
</bean>

which looks like I am doing something wrong here?

Is there any way to override beans without requiring to inject all the dependencies to the subclassing bean?

Answer 1

I can't say I remember using it myself in practice, but I think it might be the parent attribute that you're looking for:

Spring docs
Mkyong tutorial

An un-tested example using your terms:

<bean id="foo" class="biz.tugay.Foo">
  <constructor-arg ref="waldo"/>
  <property name="baz" ref="baz"/>
  <property name="qux" ref="qux"/>
  <property name="quux" ref="quux"/>
  <property name="corge" ref="corge"/>
</bean>

<bean id="thudFoo" class="biz.tugay.thud.ThudFooImpl" parent="foo"/>

I expect this won't work exactly, I don't have a project to easily test it with, but hopefully together with the docs it will get you some of the way...

Answer 2

You could make ThusFooImpl extend FooImpl by composition rather than inheritance. They should both implement a Foo interface, and you could inject an instance of FooImpl into ThudFooImpl . Then call the injected FooImpl from the 2nd branch of your if statement in ThudFooImpl .