查找本地进程的jmx url的代码

好久没写blog了，先来篇充充数。。

当想用JMX连接本地进程，而这个进程又没有配置JMX相关的参数，怎样才能连到这个进程？

下面的代码是从ActiveMQ的代码里抠出来的，可以得到本地进程的jmx url。

不过当目标进程配置了-Djava.io.tmpdir 参数时，不能正常工作，原因是JDK的bug。

参考：

http://dikar.iteye.com/blog/1415408

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6649594

所以ActiveMQ5.8在用命令行时，用 "./activemq-admin list" ，得不出结果，改用"./activemq
list "就可以了。

原因是"activemq-admin"这个脚本里，配置了一个java.io.tmpdir 的参数。

给ActiveMQ提了个issue，不过貌似没人理。。

https://issues.apache.org/jira/browse/AMQ-4541

import java.io.File;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.List;
import java.util.Properties;

public class AbstractJmxCommand  {
    private static final String CONNECTOR_ADDRESS =
        "com.sun.management.jmxremote.localConnectorAddress";

    public static String getJVM() {
        return System.getProperty("java.vm.specification.vendor");
    }

    public static boolean isSunJVM() {
        // need to check for Oracle as that is the name for Java7 onwards.
        return getJVM().equals("Sun Microsystems Inc.") || getJVM().startsWith("Oracle");
    }

    /**
     * Finds the JMX Url for a VM by its process id
     *
     * @param pid
     * 		The process id value of the VM to search for.
     *
     * @return the JMX Url of the VM with the given pid or null if not found.
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    protected String findJMXUrlByProcessId(int pid) {

        if (isSunJVM()) {
            try {
                // Classes are all dynamically loaded, since they are specific to Sun VM
                // if it fails for any reason default jmx url will be used

                // tools.jar are not always included used by default class loader, so we
                // will try to use custom loader that will try to load tools.jar

                String javaHome = System.getProperty("java.home");
                String tools = javaHome + File.separator +
                        ".." + File.separator + "lib" + File.separator + "tools.jar";
                URLClassLoader loader = new URLClassLoader(new URL[]{new File(tools).toURI().toURL()});

                Class virtualMachine = Class.forName("com.sun.tools.attach.VirtualMachine", true, loader);
                Class virtualMachineDescriptor = Class.forName("com.sun.tools.attach.VirtualMachineDescriptor", true, loader);

                Method getVMList = virtualMachine.getMethod("list", (Class[])null);
                Method attachToVM = virtualMachine.getMethod("attach", String.class);
                Method getAgentProperties = virtualMachine.getMethod("getAgentProperties", (Class[])null);
                Method getVMId = virtualMachineDescriptor.getMethod("id",  (Class[])null);

                List allVMs = (List)getVMList.invoke(null, (Object[])null);

                for(Object vmInstance : allVMs) {
                    String id = (String)getVMId.invoke(vmInstance, (Object[])null);
                    if (id.equals(Integer.toString(pid))) {

                        Object vm = attachToVM.invoke(null, id);

                        Properties agentProperties = (Properties)getAgentProperties.invoke(vm, (Object[])null);
                        String connectorAddress = agentProperties.getProperty(CONNECTOR_ADDRESS);

                        if (connectorAddress != null) {
                            return connectorAddress;
                        } else {
                            break;
                        }
                    }
                }
            } catch (Exception ignore) {
            }
        }

        return null;
    }
}