我有一个在 2 个 MBean 服务器中注册的 MXBean 实例:
@MXBean(true)
public interface I {
// ...
}
public final class C extends StandardMBean implements I {
public C() {
super(I.class, JMX.isMXBeanInterface(I.class));
}
public static void main(final String args[]) throws JMException, IOException {
final MBeanServer mBeanServer0 = ManagementFactory.getPlatformMBeanServer();
final MBeanServer mBeanServer1 = MBeanServerFactory.createMBeanServer();
final ObjectName objectName = new ObjectName("com.example:name=Foo,type=Bar");
final I i = new C();
mBeanServer0.registerMBean(i, objectName);
mBeanServer1.registerMBean(i, objectName);
// ...
}
}
该StandardMBean
实例包装了一个MXBeanSupport
. 我想稍后从两台服务器上注销我的 MBean:
mBeanServer1.unregisterMBean(objectName);
mBeanServer0.unregisterMBean(objectName);
问题是,unregister()
方法的MXBeanSupport
实现如下,显然只能调用一次:
@Override
public void unregister() {
synchronized (lock) {
if (mxbeanLookup != null) {
if (mxbeanLookup.removeReference(objectName, getResource()))
objectName = null;
}
}
}
否则,我会将 NPE 包装到RuntimeMBeanException
:
Exception in thread "main" javax.management.RuntimeMBeanException: RuntimeException thrown in postDeregister method: rethrowing <java.lang.NullPointerException>, although the MBean is sucessfully unregistered
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.postDeregisterInvoke(DefaultMBeanServerInterceptor.java:1060)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.exclusiveUnregisterMBean(DefaultMBeanServerInterceptor.java:452)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.unregisterMBean(DefaultMBeanServerInterceptor.java:415)
at com.sun.jmx.mbeanserver.JmxMBeanServer.unregisterMBean(JmxMBeanServer.java:546)
at com.example.C.main(C.java:41)
Caused by: java.lang.NullPointerException
at com.sun.jmx.mbeanserver.MXBeanLookup.removeReference(MXBeanLookup.java:159)
at com.sun.jmx.mbeanserver.MXBeanSupport.unregister(MXBeanSupport.java:169)
at javax.management.StandardMBean.postDeregister(StandardMBean.java:1137)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.postDeregisterInvoke(DefaultMBeanServerInterceptor.java:1054)
... 4 more
不过,仅从单个服务器取消注册 MBean不是一种选择。
如果不创建两个单独的 MBean 实例,我应该如何更正我的代码?