Spring, prototypes, and MBeanExporter

问题

I am using Spring in conjunction with its MBeanExporter. I have a prototype bean definition which should only be instantiated when a call to ApplicationContext.getBean() is made. However, the MBeanExporter is (incorrectly) instantiating an instance of the prototype bean when bootstrapping the container.

I found this bug report from ages ago, with no notable response.

This seems to me like it must be a common scenario, so I feel like I must be missing something. It's important that my prototype not be instantiated ahead of time, and that I can use MBeanExporter to make my JMX integration simpler. Can anyone explain what I'm doing wrong?

For reference, my spring config looks like this:

<bean id="foo" class="MyPrototypeClassName" scope="prototype"/>

<bean id="namingStrategy" class="org.springframework.jmx.export.naming.IdentityNamingStrategy"/>

<bean id="exporter" class="org.springframework.jmx.export.MBeanExporter">
    <property name="namingStrategy" ref="namingStrategy"/>
    <property name="autodetect" value="true"/>
</bean>

回答1:

I've found something of a workaround, but it's clunky so I suspect it's not best practices. I have simply changed my exporter config to:

<bean id="exporter" class="org.springframework.jmx.export.MBeanExporter">
    <property name="namingStrategy" ref="namingStrategy"/>
    <property name="autodetect" value="true"/>
    <property name="excludedBeans">
        <list>
            <value>foo</value>
        </list>
    </property>
</bean>

That way the auto-exporter ignores my prototype bean. Consequently, my prototype bean can now take a reference to the MBeanExporter (previously this was causing a unresolvable dependency cycle). So now my prototype can register and unregister itself in JMX at appropriate points.

If anyone can weigh in on whether this is a good/bad approach, I'd appreciate it.

回答2:

You could use a custom marker interface like MyJmxAutodetectExclude and extend Spring MetadataMBeanInfoAssembler. This way you don't need to tweak your context.xml each time you refactor your code

public class MyMBeanInfoAssembler extends MetadataMBeanInfoAssembler {

    @Override
    public boolean includeBean(final Class<?> beanClass, final String beanName) {
        if (super.includeBean(beanClass, beanName)) {
            List<Class<?>> list = Arrays.asList(beanClass.getInterfaces());
            if (list.contains(MyJmxAutodetectExclude.class)) {
                return false;
            }
            return true;
        }
        return false;
    }
}

来源：https://stackoverflow.com/questions/12748087/spring-prototypes-and-mbeanexporter

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