EnableLoadTimeWeaving did not weave other config in web application context

Question

I try to use spring weblogic LTW in my project to do some aop stuff. my project is a simple webapp servlet2.5 use spring mvc 3.2.6, running on weblogic 10.0. I have following app level configuration setup in web.xml

@Configuration
@EnableLoadTimeWeaving
public class AppConfig {

}


@Configuration
@EnableTransactionManagement
@ComponentScan(basePackages = { "com.blabla.model" })
public class CoreConfig {
}

I also have a mvc level configuration setup in my web.xml

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = { "com.blabla.controller" })
public class MVCConfig extends WebMvcConfigurerAdapter {
}

here is my simplified web.xml

    <context-param>
        <param-name>contextClass</param-name>
        <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext
        </param-value>
    </context-param>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>AppConfig,CoreConfig
        </param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>
    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <init-param>
            <param-name>contextClass</param-name>
            <param-value>
                org.springframework.web.context.support.AnnotationConfigWebApplicationContext
            </param-value>
        </init-param>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>MVCConfig
            </param-value>
        </init-param>
        <init-param>
            <param-name>wl-dispatch-policy</param-name>
            <param-value>RestWorkManager</param-value>
        </init-param>
        <load-on-startup>2</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

so what happens is, MVCConfig and its scanned components are all woven by LTW and works great. but CoreConfig and its scanned components (all the DAO) are not picked up by LTW.

I guess that the CoreConfig and AppConfig is in the same level, so when AppConfig and CoreConfig are loaded, the LTW is not triggered yet.

And I tried to put the CoreConfig in the same level as MVCConfig, it got picked up by LTW.

but CoreConfig is supposed to be application level, not dispatchservlet level. Since many spring web MVC applications use a root context and a child for the DispatcherServlet.

so My question is if I put CoreConfig in the app level, how to make LTW pick it up? Thanks.

Answer 1

Loadtimeweaving will only work for classes that aren't already loaded by the class loader.

Now when using XML configuration the actual bean classes are loaded after the load time weaving is enabled so it works, more or less, flawlessly for all classes.

With Java Config classes are loaded as soon as the @Configuration annotationed class is loaded. All classes that are imported are loaded into the class loader. After this load time weaving is enabled, however only for classes that are going to be loaded after this point.

Hence the fact that it is working for classes loaded by the configuration as specified for the DispatcherServlet and hence the problem in the ContextLoaderListener.

One thing you can try is to put a @ComponentScan for @Configuration classes on the AppConfig. And let the ContextLoaderListener only load the AppConfig. That might defer the class loading a little until after the load time weaving is enabled.

Something that definitely will work is putting both configuration classes in XML, remove the @EnableLoadTimeWeaving for the AppConfig and use a <context:load-time-weaving />.