[COCOON-2036] Throw an exception when circular dependencies in servlet connections are detected.

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.2
• Component/s: - Servlet service framework
• Affects version (Component): Servlet Service Framework - 1.0.0-RC1
• Fix version (Component): Servlet Service Framework - 1.0.0-RC2-dev
• Assignee: Grzegorz Kossakowski
• Reporter: Alexander Klimetschek
• Created: 03/Apr/07 19:39
• Updated: 13/Jan/08 12:40
• Resolved: 13/Jan/08 12:40

Description

Circular dependencies in servlet connections lead to a Spring exception [1] in [2] that does not provide any help. The previous implementation (block:) did allow circular dependencies because they were not handled by spring but by custom code.

Solution would be either to allow them (probably difficult to implement with spring) or, if not, to provide a helpful warning message, that skips this problem. The latter could be a check for embeddedServlet==null and, if not, throw an exception saying "you might have a circular dependency in <servlet-foobar>".

---

[1]:

The exception is thrown after ServletFactoryBean.getObject() tries to create a proxy for the embeddedServlet, which is null in the case of a circular dependency (one of the circle endpoints is created, but the other will be null).

Caused by: org.springframework.aop.framework.AopConfigException: Can't proxy null object
        at org.springframework.aop.framework.ProxyFactory.<init>(ProxyFactory.java:49)
        at org.apache.cocoon.servletservice.spring.ServletFactoryBean.getObject(ServletFactoryBean.java:194)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectFromFactoryBean(AbstractBeanFactory.java:1211)

[2]:
    public Object getObject() throws Exception {
        ProxyFactory proxyFactory = new ProxyFactory(this.embeddedServlet);
        proxyFactory.addAdvice(new ServiceInterceptor());
        if (this.mountPath != null) {
            proxyFactory.addAdvisor(new MountableMixinAdvisor());
        }
        proxyFactory.addAdvisor(new ServletServiceContextMixinAdvisor());
        return proxyFactory.getProxy();
    }

Issue Links

• is related to: COCOON-2038 Implement true Object Oriented approach for handling super calls