Java EE servlet as spring bean proxy

Question

I have servlet named com.sample.servlets.CreateReleaseServlet for which I am trying to add spring AOP advice in a helper method.

I have the following code in spring config file:

<bean id="customerService" class="com.sample.servlets.CreateReleaseServlet">
</bean>

<bean id="notificationAdvice" class="com.sample.advice.NotificationAdvice" />

<bean id="customerServiceProxy" class="org.springframework.aop.framework.ProxyFactoryBean">

    <property name="target" ref="customerService" />

    <property name="interceptorNames">
        <list>
            <value>notificationAdvice</value>
        </list>
    </property>
</bean>

When I try to get this servlet as bean by using the following Java code:

ApplicationContext appContext = new ClassPathXmlApplicationContext(
        new String[] { "/WEB-INF/form-servlet.xml" });
CreateReleaseServlet servlet = (CreateReleaseServlet) appContext.getBean("customerServiceProxy");

String next = servlet.execute(req);

I get the following exception:

 com.ibm.ws.webcontainer.webapp.WebApp logServletError SRVE0293E: [Servlet Error]-[CreateReleaseServlet]: java.lang.ClassCastException: $Proxy103 incompatible with com.sample.servlets.CreateReleaseServlet
        at com.sample.servlets.CreateReleaseServlet.service(CreateReleaseServlet.java:1823)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
        at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1229)
        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:774)
        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:456)
        at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178)
        at com.ibm.ws.webcontainer.filter.WebAppFilterChain.invokeTarget(WebAppFilterChain.java:136)
        at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:97)
        at com.sample.servlets.SampleFilter.doFilter(Unknown Source)
        at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:195)
        at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:91)
        at com.ibm.ws.webcontainer.filter.WebAppFilterManager.doFilter(WebAppFilterManager.java:928)
        at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1025)
        at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3751)
        at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:304)
        at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:962)
        at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1662)
        at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195)
        at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:452)
        at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:511)
        at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:305)
        at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:83)
        at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
        at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
        at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
        at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
        at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
        at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
        at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
        at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1690)

Any suggestion will be of great help

Answer 1

Unless you have enabled proxying of classes (and not plain JdkProxy of interfaces), this will not work, as the proxy object will not act as a subclass of your servlet. You could probably cast it to an instance of Servlet instead. That said, your approach does seem a little strange. What do your interceptor do? The common way of doing AOP(ish) stuff with servlets is to create a servlet filter. And if that's not an option, I suggest you convert your servlet to a Spring MVC controller and use regular Spring MVC options for configuring interceptors.