Spring MVC: Why does this declaration work,

Question

I'm trying to add some HandlerInterceptorAdaptors to ALL of my Controllers/Actions in Spring MVC. I'm adding these to my servlet XML file.

What I don't understand, is why the <mvc:interceptors> block I have below is working, but not the traditional bean declaration with DefaultAnnotationHandlerMapping.

Here is the XML that is working:

<mvc:interceptors>
    <bean name="interceptor1" class="com.foo.bar" />
    <bean name="interceptor2" class="com.foo.bar2" />
</mvc:interceptors>

Here is the XML that I can't get to work:

<bean name="interceptor1" class="com.foo.bar" />
<bean name="interceptor2" class="com.foo.bar2" />
<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
    <property name="order" value="0" />
    <property name="interceptors">
        <list>
            <ref bean="interceptor1"/>
            <ref bean="interceptor2"/>
        </list>
    </property>
</bean>

I thought that Spring would automatically pick up my bean of type DefaultAnnotationHandlerMapping, but that doesn't seem to be the case.

Note that I'm annotating all of my Controller classes with @Controller and the methods within the Controller with @RequestMapping.

Any thoughts?

Answer 1

Spring is actually constructing one "MappedInterceptor" for each bean (org.springframework.web.servlet.handler.MappedInterceptor).

When I want to understand a Spring NamespaceHandler, I find it crucial to look at the source code (for the NamespaceHandler and then the BeanDefinitionParser).

The MvcNamespaceHandler pointed me to this InterceptorsBeanDefinitionParser ...

http://javasourcecode.org/html/open-source/spring/spring-3.0.5/org/springframework/web/servlet/config/InterceptorsBeanDefinitionParser.java.html

This indicates that you should be building a bean for each 'interceptor', a little bit like this...

<bean name="interceptor1" class="com.foo.bar" />
<bean name="interceptor2" class="com.foo.bar2" />
<bean class="org.springframework.web.servlet.handler.MappedInterceptor">
    <constructor-arg index="0">
        <null />
    </constructor-arg>
    <constructor-arg index="1">
        <ref bean="interceptor1"/>
    </constructor-arg>
</bean>
<bean class="org.springframework.web.servlet.handler.MappedInterceptor">
    <constructor-arg index="0">
        <null />
    </constructor-arg>
    <constructor-arg index="1">
        <ref bean="interceptor2"/>
    </constructor-arg>
</bean>

This will almost-definitely need some tinkering, but it gets you a lot closer to what Spring is doing ...

Give it a try, and if it doesn't work first-time, look harder at the source code I've linked to above.

HTH