MBeanExporter fails against null beans [SPR-15031]

[spring-projects-issues]

Vadim Beilin opened SPR-15031 and commented

org.springframework.jmx.export.MBeanExporter#registerBeanNameOrInstance(Object,String) may encounter situation when the bean value returned by the getBean(beanName) at line 601 is null. One common situation when this happens is when a FactoryBean.getObject() returns null (valid since Spring 2.0) based on some configuration settings.

MBeanExporter or its subclasses cannot deal with this situation:

• MBeanExporter:

Exception in thread "main" org.springframework.jmx.export.UnableToRegisterMBeanException: Unable to register MBean [spring.SpringTest$Fct] with key 'spring.SpringTest$Fct'; nested exception is javax.management.MalformedObjectNameException: Key properties cannot be empty
	at org.springframework.jmx.export.MBeanExporter.registerBeanNameOrInstance(MBeanExporter.java:625)
	at org.springframework.jmx.export.MBeanExporter.registerBeans(MBeanExporter.java:550)
	at org.springframework.jmx.export.MBeanExporter.afterSingletonsInstantiated(MBeanExporter.java:432)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:792)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
	at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
	at spring.SpringTest.main(SpringTest.java:15)
Caused by: javax.management.MalformedObjectNameException: Key properties cannot be empty
	at javax.management.ObjectName.construct(ObjectName.java:483)
	at javax.management.ObjectName.<init>(ObjectName.java:1382)
	at javax.management.ObjectName.getInstance(ObjectName.java:1273)
	at org.springframework.jmx.support.ObjectNameManager.getInstance(ObjectNameManager.java:62)
	at org.springframework.jmx.export.naming.KeyNamingStrategy.getObjectName(KeyNamingStrategy.java:141)
	at org.springframework.jmx.export.MBeanExporter.getObjectName(MBeanExporter.java:751)
	at org.springframework.jmx.export.MBeanExporter.registerBeanInstance(MBeanExporter.java:654)
	at org.springframework.jmx.export.MBeanExporter.registerBeanNameOrInstance(MBeanExporter.java:602)
	... 7 more

• AnnotationMBeanExporter:

Exception in thread "main" org.springframework.jmx.export.UnableToRegisterMBeanException: Unable to register MBean [spring.SpringTest$Fct] with key 'spring.SpringTest$Fct'; nested exception is java.lang.IllegalArgumentException: Candidate object must not be null
	at org.springframework.jmx.export.MBeanExporter.registerBeanNameOrInstance(MBeanExporter.java:625)
	at org.springframework.jmx.export.MBeanExporter.registerBeans(MBeanExporter.java:550)
	at org.springframework.jmx.export.MBeanExporter.afterSingletonsInstantiated(MBeanExporter.java:432)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:792)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
	at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
	at spring.SpringTest.main(SpringTest.java:15)
Caused by: java.lang.IllegalArgumentException: Candidate object must not be null
	at org.springframework.util.Assert.notNull(Assert.java:115)
	at org.springframework.aop.support.AopUtils.getTargetClass(AopUtils.java:104)
	at org.springframework.jmx.export.naming.MetadataNamingStrategy.getObjectName(MetadataNamingStrategy.java:111)
	at org.springframework.jmx.export.MBeanExporter.getObjectName(MBeanExporter.java:751)
	at org.springframework.jmx.export.MBeanExporter.registerBeanInstance(MBeanExporter.java:654)
	at org.springframework.jmx.export.MBeanExporter.registerBeanNameOrInstance(MBeanExporter.java:602)
	... 7 more

Example for reproduction:

package spring;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.context.annotation.*;
import org.springframework.jmx.export.MBeanExporter;

@Configuration
@Import({/*AnnotationMBeanExporter.class*/MBeanExporter.class, SpringTest.Fct.class})
public class SpringTest {
    public static void main(String[] args) { new AnnotationConfigApplicationContext(SpringTest.class);   }
    
    public static class Fct implements FactoryBean<Something> {
        // returns null if some condition is not met 
        @Override public Something getObject() throws Exception { return null; }
        @Override public Class<?> getObjectType() { return Something.class; }
        @Override public boolean isSingleton() { return true; }
    }
    
// uncomment to use AnnotatedMBeanExporter
//    @ManagedResource
    public static class Something implements SomethingMBean{}
    public static interface SomethingMBean {}
}

Tested with 4.2.6, code in either 4.3.x or 5. does not appear to have any changes.

---

Affects: 3.2.17, 4.2.6

Backported to: 4.2.9, 3.2.18

[spring-projects-issues]

Juergen Hoeller commented

Without a dedicated ObjectNamingStrategy, it even fails with an NPE later on...
I've addressed this through corresponding not-null checks, silently ignoring such null beans now.

Thanks for the report!