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我正在使用jdk1.6。我已经在运行时成功加载了一个 jar。代码如下:

vm = VirtualMachine.attach(vid);
vm.loadAgent(agentPath);

现在我想在运行时卸载这个代理。没有 API DOC 可以做到这一点。谁能给我一些建议?谢谢。

编辑

更多代码

GlobalVariables.vm = VirtualMachine.attach(vid);

// Check to see if transformer agent is installed
if(!GlobalVariables.vm.getSystemProperties().contains("demo.agent.installed")) {
    System.out.println("Load agent");

    GlobalVariables.vm.loadAgent(agentPath); 

}

GlobalVariables.connectorAddress = GlobalVariables.vm.getAgentProperties().getProperty("com.sun.management.jmxremote.localConnectorAddress", null);
if(null == GlobalVariables.connectorAddress) {
    // It's not, so install the management agent
    String javaHome = GlobalVariables.vm.getSystemProperties().getProperty("java.home");
    File managementAgentJarFile = new File(javaHome + File.separator + "lib" + File.separator + "management-agent.jar");
    GlobalVariables.vm.loadAgent(managementAgentJarFile.getAbsolutePath());
    System.out.println("Load Management agent");
    GlobalVariables.connectorAddress = GlobalVariables.vm.getAgentProperties().getProperty("com.sun.management.jmxremote.localConnectorAddress", null);
    // Now it's installed
}

// Now connect and transform the classnames provided in the remaining args.
//JMXConnector connector = null;
try {
    // This is the ObjectName of the MBean registered when loaded.jar was installed.
    //ObjectName on = new ObjectName("transformer:service=DemoTransformer");
    GlobalVariables.on = new ObjectName("transformer:service=DemoTransformer");
    // Here we're connecting to the target JVM through the management agent
    GlobalVariables.connector = JMXConnectorFactory.connect(new JMXServiceURL(GlobalVariables.connectorAddress));
    GlobalVariables.server = GlobalVariables.connector.getMBeanServerConnection();
    System.out.println("MBean Server connection...");

    // Call transformClass on the transformer MBean
    GlobalVariables.server.invoke(GlobalVariables.on, "transformClass", new Object[]{className, args}, new String[]{String.class.getName(), String.class.getName()});

} catch (Exception ex) {
    ex.printStackTrace(System.err);
} finally {
    if(GlobalVariables.connector!=null) try { GlobalVariables.connector.close(); } catch (Exception e) {}
    GlobalVariables.vm.detach();
    System.out.println("Has disconnected");
}

我当时做了什么

我再次运行上述代码以再次加载这两个代理。但我有错误。

错误

当前虚拟机中的错误

com.sun.tools.attach.AgentInitializationException: Agent JAR loaded but agent failed to initialize
    at sun.tools.attach.HotSpotVirtualMachine.loadAgent(HotSpotVirtualMachine.java:103)
    at com.sun.tools.attach.VirtualMachine.loadAgent(VirtualMachine.java:508)
    at faultinjectionaction.AttachClass.attachAgent(AttachClass.java:111)
    at org.apache.jsp.fjstep3_jsp._jspService(fjstep3_jsp.java:350)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:619)

目标虚拟机错误

Exception in thread "Attach Listener" java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:323)
        at sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:348)
Caused by: javax.management.InstanceAlreadyExistsException: transformer:service= DemoTransformer
        at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:453)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.internal_addObject(DefaultMBeanServerInterceptor.java:1484)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:963)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:917)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:312)
        at com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:482)
        at faultinjectionagent.AgentMain.agentmain(AgentMain.java:28)
        ... 6 more

目标

做同样的工作没有错误。我想我每次完成工作后都需要卸下代理。但是我没有卸载那些代理。

编辑 GlobleVariables

import javax.management.MBeanServerConnection;
import javax.management.ObjectName;
import javax.management.remote.JMXConnector;
import com.sun.tools.attach.VirtualMachine;

public class GlobalVariables{
    public static MBeanServerConnection server;
    public static ObjectName on;
    public static JMXConnector connector = null;
    public static String connectorAddress = null;
    public static VirtualMachine vm;
}
4

1 回答 1

2

卸载代理是什么意思?您不能像文档中隐含的那样卸载类:

将指定的 JAR 文件添加到(目标虚拟机的)系统类路径中

解决这个问题的唯一方法可能是一些自定义类加载器的魔法,但我不建议这样做。

更新:查看您的扩展问题后,我认为您的问题实际上是其他问题。在某些时候你正在调用

JMXConnectorFactory.connect(new JMXServiceURL(GlobalVariables.connectorAddress))

为了创建一个JMXConnector. 我猜在您的GlobalVariables.server.invoke通话中,您正在通过new ObjectName("transformer:service=DemoTransformer"). 此名称必须是唯一的,并且当您第二次运行代码时,此名称已按照javax.management.InstanceAlreadyExistsException: transformer:service= DemoTransformer. 你需要做的是:

  • 在第二次注册 MBean 时选择另一个名称。
  • 在从远程 JVM 分离之前调用MBeanServerConnection.close(new ObjectName("transformer:service=DemoTransformer")),以使名称再次可用。

您可能假设通过分离,远程计算机上的所有状态都已重置。然而,这不是真的。您添加了一个具有名称的 MBean,然后您再次尝试执行此操作。这个错误可以理解为好像你在一个映射中添加了一个具有相同键的两个值。但是,除了地图之外,您不会覆盖值,但会导致您在上面观察到的异常。

顺便说一句:JMXConnector.close当不再需要与远程服务器的连接时,您应该显式调用。

PS:你可能会觉得这篇文章很有趣。

更新 2:在聊天中讨论并解决 MBean 命名冲突之后,我认为这是导致问题的原因:

当第二次加载 Java 代理时,代理附带的类(在 中表示managementAgentJarFile)已经加载到目标 JVM 中。这意味着,不会再次运行任何类初始化程序,并且static仍将表示由变量表示的状态更改。此外,无法加载具有相同名称但更改了实现的类。这将导致LinkageErrors 和代理加载将失败。解决方案是避免static一个代理不能影响自己的状态,并为不同的代理创建单独的名称空间。否则,可以使用自定义类加载器卸载代理类。可以在许多地方和此处找到有关此问题的更多信息:

于 2013-11-27T10:21:06.417 回答