lookup-method Problem

[neketsushonen]

Hello Every Body:

I had a problem that make I feel impossible to solve with lookup-method:

I define two class witch have same method name "sayHello":

public class ClassA {
	public String sayHello(){
		return "Hello: class A";		
	}

public class ClassB {
	public String sayHello(){
		return "Hello: class B";		
	}
}
}

Then, in my spring-config.xml I defined:

        <bean id="a" class="ClassA">
	</bean>
	<bean id="b" class="ClassB">
		<lookup-method name="sayHello" bean="a"/>
	</bean>

When I did my test:

ApplicationContext context = new ClassPathXmlApplicationContext("spring/test.xml");
		ClassB b = (ClassB)context.getBean("b");
		System.out.println(b.sayHello());

that throws a Exception:

java.lang.ClassCastException
	at ClassB$$EnhancerByCGLIB$$9bd3da22.sayHello(<generated>)
	at TestSpring.testMethodLookup(TestSpring.java:10)

I don´t know why? I am using cglib-2.1.2.jar... that´s a possible problem?

[Mark Fisher]

The method you are replacing (the "sayHello" method) returns a String object. However, by using the lookup-method, you are returning an object of type "ClassA" rather than the expected String.

[neketsushonen]

Thank you Mark, again you helpme to solve my problem.

I has other problem:

does the method witch specific by lookup-method always returning a same Object? Let me quote your answer:

by using the lookup-method, you are returning an object of type "ClassA" rather than the expected String

so, does method sayHello always return a Object ClassA and nothing more?

[Mark Fisher]

In the lookup-method element, the "name" attribute is the method to be replaced, and the "bean" attribute is the bean to be looked-up and returned instead.

In the definition of bean "b" you have:
<lookup-method name="sayHello" bean="a"/>

Therefore, whenever b's sayHello() method is called, the object defined as bean a will be returned. The return value of sayHello() is a String whereas bean a is not a String. That is the source of the ClassCastException.

If you are actually interested in arbitrary method replacement, then you can read about it in the reference doc here: http://static.springframework.org/sp...s.html#d0e1197