在JVM中有一些常用的MBeans，可以写个代码获取到：
public class Test {
public static void main(String[] args) throws Exception {
MBeanServer server = ManagementFactory.getPlatformMBeanServer();
Set instances = server.queryMBeans(null, null);
Iterator iterator = instances.iterator();
while (iterator.hasNext()) {
ObjectInstance instance = (ObjectInstance) iterator.next();
System.out.println("MBean Found:");
System.out.println("Class Name:\t" + instance.getClassName());
System.out.println("Object Name:\t" + instance.getObjectName());
System.out.println("****************************************");
}
}
}
根据列表，我们就能通过MBean来获取想要的信息了，比如获取Code Cache的大小：
public class TestMBean {
final static String pid = "6228";
final static String CONNECTOR_ADDRESS = "com.sun.management.jmxremote.localConnectorAddress";
public static void main(String[] args) throws Exception {
VirtualMachine vm = VirtualMachine.attach(pid);
JMXConnector connector = null;
String connectorAddress = vm.getAgentProperties().getProperty(CONNECTOR_ADDRESS);
String agent = vm.getSystemProperties().getProperty("java.home") + File.separator + "lib" + File.separator
+ "management-agent.jar";
vm.loadAgent(agent);
connectorAddress = vm.getAgentProperties().getProperty(CONNECTOR_ADDRESS);
JMXServiceURL url = new JMXServiceURL(connectorAddress);
connector = JMXConnectorFactory.connect(url);
MBeanServerConnection mbeanConn = connector.getMBeanServerConnection();
ObjectName name = new ObjectName("java.lang:type=MemoryPool,name=Code Cache");
System.out.println(mbeanConn.getAttribute(name, "Usage"));
if (connector != null) {
connector.close();
}
vm.detach();
}
}
实际上通过ObjectName("java.lang:type=MemoryPool,name=Code Cache")得到的类为：
sun.management.MemoryPoolImpl
而在getAttribute(name, "Usage")的时候对应调用的方法为:
public java.lang.management.MemoryUsage getUsage(){}
其他MBean的用法和这个类似。