proxy for @Controller annotated class

[oae]

Hi there,

converting Controllers of a spring mvc project from traditional style to new 2.5 annotation based controllers give me following proxy problems.

The interesting part of the class:
Note that the class implements no interface and has no default constructor.

@Controller
@RequestMapping("/login")
@SessionAttributes("login")
public class LoginController {

    @Autowired
    public LoginController(IUserService userService) {
        _userService = userService;
    }
... 

The aop setup look as follow:

<bean
        class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
        <property name="beanNames">
            <list>
                <value>*Controller</value>
            </list>
        </property>
        <property name="interceptorNames">
            <list>
                <value>permissionAdvice</value>
            </list>
        </property>
    </bean> 

The controller class gets instantiated via DefaultAnnotationHandlerMapping.class.
Loading the context results in following exception:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'loginController': Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class com.project.web.controller.LoginController]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:547)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:485)
        at java.security.AccessController.doPrivileged(Native Method)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:455)
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:251)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:169)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:248)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:170)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:413)
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:735)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:369)
        at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:332) 

If i use setter- instead of contructor-injection everythings work fine.
If i let the controller implement any interface (like Serializable) the context-loading happens without exception, but it comes to

javax.servlet.ServletException: No adapter for handler [com.project.web.controller.LoginController@ef77e9]: Does your handler implement a supported interface like Controller?
    at org.springframework.web.servlet.DispatcherServlet.getHandlerAdapter(DispatcherServlet.java:1086) 

Does anyone have a clue whats happening here ?
Johannes

[Marten Deinum]

For CGLib proxies to work, as the error message also clearly stated, you need to have a no-arg constructor. It is a requirement for CGLib proxies.

If you implement an interface like Serializable a JDK Dynamic proxy is created which only works with interfaces not classes. So your proxy is only an instance/castable to Serializable it isn't a Controller anymore (in the case of a @Controller, if you would implement the Controller interface it would work).

[oae]

Thanks,

that makes sense. So the best workaround seems to me to add a protected default constructor.

@Controller
@RequestMapping("/login")
@SessionAttributes("login")
public class LoginController {

    protected LoginController() {
        // needed for aop cglib
    }

    @Autowired
    public LoginController(IUserService userService) {
        _userService = userService;
    } 

No everything works. Proxy instantiation and IOC.
Thanks!

[swetha]

I'm facing similar issue

I'm using spring AOP's around advice to capture processing time of a transaction. I'm getting the following error during application startup

error creating bean "coreMessageResourceAccesor"
   Could not generate CGLIB subclass of class 
     [class org.springframework.context.support.MessageSourceAccessor]: 
Common causes of this problem include using a final class or a non-visible class; 
nested exception is java.lang.IllegalArgumentException: 
   Superclass has no null constructors but no arguments were given

Below is the configuration for the bean

<bean id="coreMessageSourceAccessor"  class="org.springframework.context.support.MessageSourceAccessor" >
    <constructor-arg type="org.springframework.context.MessageSource" ref="coreMessageSource" />
</bean>

In my case, I cannot add no-arg constructor since the bean is using "MessageSourceAccessor" a Spring class. And also "MessageSourceAccessor" doesn't implement any interface so, jdk proxy will not work.

please advise.