NotWritablePropertyException with Spring framework

There must be some subtlety in the way my class variables are being looked at by Spring. I've reviewed the associated files and am unable to spot where I am being inconsistent with something. Can you help me find what it is?

The error I'm getting is:

org.springframework.beans.NotWritablePropertyException: Invalid property 'memberVariableClass' of bean class [ClassName]: Bean property 'memberVariableClass' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

Here's the top-level bean, ClassName.java:

import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.springframework.http.HttpHeaders;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class ClassName {

    private MemberVariableClass memberService;
    // private EditorService spanishEditorService;

    public ClassName() {

    }

    // public ClassName(MemberVariableClass memberVariableClassArgument) {
    //  this.memberService = memberVariableClassArgument;
    // }

    @ResponseBody
    @RequestMapping(value = "/")
    public String helloWorld()
    {
        return "Hello world!";
    }

    public void setMemberService(MemberVariableClass memberService) {
        this.memberService = memberService;
    }
}

Here's the MemberVariableClass interface followed by its implementation:

/* 
 * The old EditorService. 
 * Probably be best if name was MemberVariableClassInterface... for now.
 */
public interface MemberVariableClass {

    public String dummyMethod();

    public String getAttribute();

}

public class MemberVariableClassImpl implements MemberVariableClass {

    String attribute = "value";

    public String dummyMethod() {
        return "Hi I'm a dummy method.";
    }

    public String getAttribute() {
        return this.attribute;
    }
}

and finally, here's the servletContext.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://ift.tt/GArMu6"
       xmlns:xsi="http://ift.tt/ra1lAU"
       xmlns:mvc="http://ift.tt/1bHqwjR"
       xsi:schemaLocation="http://ift.tt/GArMu6
            http://ift.tt/1cnl1uo
            http://ift.tt/1bHqwjR
            http://ift.tt/1kF4x7W">

    <mvc:annotation-driven />

    <bean name="className" class="ClassName">
        <property name="memberService" ref="memberVariableClassImpl" />
    </bean>

    <bean name="memberVariableClassImpl" class="MemberVariableClassImpl" />    
</beans>