MBean与JMX

忘是亡心i 2021-12-11 05:23 320阅读 0赞

### MBean与JMX ###

*   *  JMX
     *  MBeanServer
     *  Agent
     *  Agent Service
     *  Protocol Adaptors and Connectors
     *   *  Protocol Adaptors
         *  Connectors
     *  MBean
     *   *  Standard MBean
     *  使用JConsole工具监控
     *  源码分析
     *   *  ManagementFactory.getPlatformMBeanServer()
         *  MBeanServerFactory.createMBeanServer()
         *  LocateRegistry.createRegistry
         *  MBeanServer.registerMBean
     *  JmxMBeanServer
     *  JMXConnectorServerFactory.newJMXConnectorServer
     *  jmxConnectorServer.start()

欢迎查看Eetal的第二十二篇博客–MBean与JMX

## JMX ##

JMX(java Management Exetensions)在Java编程语言中定义了应用程序以及网络管理和监控的体系结构、设计模式、应用程序接口以及服务。  
通常使用JMX来监控系统的运行状态或管理系统的某些方面，比如清空缓存、重新加载配置文件等  
优点是可以非常容易的使应用程序被管理  
伸缩性的架构使每个JMX Agent Service可以很容易的放入到Agent中，每个JMX的实现都提供几个核心的Agent Service，你也可以自己编写服务，服务可以很容易的部署，取消部署。  
主要作用是提供接口，允许有不同的实现  
简单来说，jmx是一个用来管理javaBean并可以进行监控的扩展规范，结合MBeanServer、rmi与http等可以作为一个服务监控和提供中心

## MBeanServer ##

MBeanServer是JMX代理的核心组件。  
它是在代理中向管理操作公开的对象的注册表。  
向MBeanServer注册的任何对象都对管理应用程序可见。  
MBeanServer仅公开MBean的管理接口，而不是它的直接对象引用。  
您要从代理的Java VM外部管理的任何资源都必须在MBeanServer中注册为MBean。  
MBeanServer还提供标准化接口，用于访问同一Java VM中的MBean，为本地对象提供操作可管理资源的所有好处。  
需要注意的是，一般不使用MBeanServerFactory.createMBeanServer()，使用ManagementFactory.getPlatformMBeanServer()  
后者在当前尚未在ManagementFactory中注册静态成员MBeanServer时，会先使用MBeanServerFactory.createMBeanServer()创建一个MBeanServer并将其注册到静态成员，后续每次调用会直接返回该成员实例  
并且ManagementFactory.getPlatformMBeanServer()方法在第一次调用createMBeanServer()实例化MBeanServer以后，会读取PlatformComponent枚举的枚举值，将一些系统必要的MBean注册到MBeanServer  
JConsole监控的MBeanServer就是在ManagementFactory中注册的静态成员MBeanServe  
所以如果没有特殊配置的MBeanServer，jconsole是不会监控的

## Agent ##

Java Management Extensions（JMX）Agent是一个在Java虚拟机（Java VM）中运行的管理实体.  
充当MBean和管理应用程序(JConsole等)之间的联络人  
Agent只是一个规范，一般会封装我们创建和启动MBeanServer以及注册MBean的过程在一个Agent行为里，方便启动

## Agent Service ##

Agent Service是可以对MBeanServer中注册的MBean执行管理操作的对象。  
通过将管理智能包含在代理中，JMX可帮助您构建更强大的管理解决方案。  
Agent Service通常也是MBean，允许通过MBeanServer控制它们及其功能。  
JMX规范定义了以下Agent Service：  
通过管理applet（m-let）服务的动态类加载检索并实例化从网络动态下载的新类和本机库。  
监视器观察MBean属性的数字或字符串值，并可以向其他对象通知几种类型的更改。  
定时器提供调度机制，并且可以以预定间隔发送通知。  
关系服务定义MBean之间的关联并维护关系的一致性。

## Protocol Adaptors and Connectors ##

Protocol adaptors and connectors使代理可从远程(通过rmi或者http等协议)管理应用程序访问。  
它们通过在MBean服务器中实例化和注册的MBean的特定协议提供视图。  
它们使Java VM外部的管理应用程序能够：  
获取或设置现有MBean的属性  
对现有MBean执行操作  
实例化并注册新的MBean  
注册并接收MBean发出的通知  
因此，要使JMX代理易于管理，它必须至少包含一个协议适配器或连接器。  
Java SE平台包括标准RMI连接器。Agent可以包括任意数量的协议适配器和连接器，允许通过不同的协议同时远程管理和监视它

### Protocol Adaptors ###

Protocol Adaptors通过给定协议提供JMX代理的管理视图。  
它们将MBean和MBean服务器的操作调整为给定协议中的表示，  
并可能调整为不同的信息模型，例如SNMP。Java SE平台不包括任何协议适配器作为标准。  
连接到Protocol Adaptors的管理应用程序通常特定于给定的协议。  
这通常是依赖于特定管理协议的传统管理解决方案的情况。  
它们不是通过MBean服务器的远程表示来访问JMX代理，而是通过映射到MBeanServer的操作来访问JMX代理。

### Connectors ###

Connectors用于将代理与为JMX技术启用的远程管理应用程序连接，即使用JMX规范的分布式服务开发的管理应用程序。  
这种通信涉及Agent中的连接器服务器和管理器中的连接器客户端。  
这些组件以特定协议的方式透明地传递管理操作。  
JMX Remote API为MBeanServer提供远程接口，管理应用程序可以通过该接口执行操作。  
Connectors特定于给定协议，但管理应用程序可以无差别地使用任何Connectors，因为它们具有相同的远程接口。

## MBean ##

描述一个可管理的资源。是一个java对象，遵循以下一些规则：  
1.必须是公用的，非抽象的类  
2.必须有至少一个公用的构造器  
3.必须实现它自己的相应的MBean接口或者实现javax.management.DynamicMBean接口  
4.可选的，一个MBean可以实现javax.management.NotificationBroadcaster接口MBean的类型  
MBean使用ObjectName以keyValue形式注册到MBeanServer上

### Standard MBean ###

标准MBean，也是最简单的MBean，通过类实现的接口名称来识别MBean  
接口名称以MBean结尾，实现类需要匹配接口名称的前半部分

public interface YytMBean{ 
    	public void setName(String name);
    	public String getName();
    }

public class Yyt implements YytMBean{ 
    	private String name;
    	@Override
    	public void setName(String name) { 
    		this.name = name;
    	}
    	@Override
    	public String getName() { 
    		return name;
    	}
    }

public class YytAgent{ 
    	private String domainName;
    	private int rmiPort;
    	public YytAgent(String domainName,int rmiPort) { 
    		this.domainName = domainName;
    		this.rmiPort = rmiPort;
    	}
    	public void start() throws MalformedObjectNameException, InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException, IOException { 
    		//MBeanServerFactory.createMBeanServer();	//don't use this
    		MBeanServer mBeanServer = ManagementFactory.getPlatformMBeanServer();	//use this instead
    		
    		YytMBean yytMBean = new Yyt();
    		ObjectName objectName = new ObjectName(domainName+":name=Yyt");
    		mBeanServer.registerMBean(yytMBean, objectName);
    		
    		LocateRegistry.createRegistry(rmiPort);//开启rmi端口监听，在jmxConnectorServer.start()时会根据serviceUrl建立一个rmiServer监听该rmi端口
    		
    		JMXServiceURL url = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://localhost:"+rmiPort+"/"+domainName);
            JMXConnectorServer jmxConnectorServer = JMXConnectorServerFactory.newJMXConnectorServer(url, null, mBeanServer);
            jmxConnectorServer.start();
            //开启jmx协议的监控服务器，因为java自带rmi的工具和依赖，可以直接开启，通过jconsole等支持jmx协议的客户端可以监控MBeanServer	
    	}
    }

## 使用JConsole工具监控 ##

JConsole是java自带的监控程序，独立jre中没有，jdk下的jre具备

运行java应用时带上参数  
\-Dcom.sun.management.jmxremote  
\-Dcom.sun.management.jmxremote.port=8999  
\-Dcom.sun.management.jmxremote.authenticate=false  
\-Dcom.sun.management.jmxremote.ssl=false  
关闭ssl和密码校验，开启远程监控端口8999，这时可以直接使用jconsole进行链接

或者在jdk\\jre\\lib\\management目录下，复制一份jmxremote.password.template的文件，改名去掉.template后缀，并去掉文件末尾两行示例的用户名和密码注释，修改密码为自己想要的  
运行加上参数  
\-Djava.rmi.server.hostname=应用所在服务器的ip或者域名  
\-Dcom.sun.management.jmxremote  
\-Dcom.sun.management.jmxremote.port=监控端口  
\-Dcom.sun.management.jmxremote.rmi.port=rmi监控端口（一般与监控端口保持一致）  
\-Dcom.sun.management.jmxremote.authenticate=true  
\-Dcom.sun.management.jmxremote.ssl=false  
这时使用JConsole链接会提示需要输入用户名和密码

在命令行输入jconsole运行jconsole程序  
![jconsole][]\]  
在jconsole的界面，因为是本地，直接选择本地进程，进入监控页面  
点击导航栏的MBean即可看到我们注册的MBean在列表中  
![jconsole][jconsole 1]  
还可以对Bean的属性值进行查看和设置  
![jconsole][jconsole 2]\]

## 源码分析 ##

### ManagementFactory.getPlatformMBeanServer() ###

SecurityManager sm = System.getSecurityManager();
            if (sm != null) { 
                Permission perm = new MBeanServerPermission("createMBeanServer");
                sm.checkPermission(perm);
            }
    
            if (platformMBeanServer == null) { 
                platformMBeanServer = MBeanServerFactory.createMBeanServer();
                for (PlatformComponent pc : PlatformComponent.values()) { 
                    List<? extends PlatformManagedObject> list =
                        pc.getMXBeans(pc.getMXBeanInterface());
                    for (PlatformManagedObject o : list) { 
                        // Each PlatformComponent represents one management
                        // interface. Some MXBean may extend another one.
                        // The MXBean instances for one platform component
                        // (returned by pc.getMXBeans()) might be also
                        // the MXBean instances for another platform component.
                        // e.g. com.sun.management.GarbageCollectorMXBean
                        //
                        // So need to check if an MXBean instance is registered
                        // before registering into the platform MBeanServer
                        if (!platformMBeanServer.isRegistered(o.getObjectName())) { 
                            addMXBean(platformMBeanServer, o);
                        }
                    }
                }
                HashMap<ObjectName, DynamicMBean> dynmbeans =
                        ManagementFactoryHelper.getPlatformDynamicMBeans();
                for (Map.Entry<ObjectName, DynamicMBean> e : dynmbeans.entrySet()) { 
                    addDynamicMBean(platformMBeanServer, e.getValue(), e.getKey());
                }
                for (final PlatformManagedObject o :
                                           ExtendedPlatformComponent.getMXBeans()) { 
                    if (!platformMBeanServer.isRegistered(o.getObjectName())) { 
                        addMXBean(platformMBeanServer, o);
                    }
                }
            }
            return platformMBeanServer;

ManagementFactory中定义一个platformMBeanServer成员来装载创建好的MBeanServer  
在执行该方法的第一步会先校验当前安全权限  
在platformMBeanServer尚未绑定一个实例时，会先使用MBeanServerFactory.createMBeanServer()实例一个MBeanServer对象  
接下来主要是读取PlatformComponent.values()以及别的枚举类和helper类的值和成员，将系统预设的MBean注册到MBeanServer

enum PlatformComponent { 
    
        /**
         * Class loading system of the Java virtual machine.
         */
        CLASS_LOADING(
            "java.lang.management.ClassLoadingMXBean",
            "java.lang", "ClassLoading", defaultKeyProperties(),
            true, // singleton
            new MXBeanFetcher<ClassLoadingMXBean>() { 
                public List<ClassLoadingMXBean> getMXBeans() { 
                    return Collections.singletonList(ManagementFactoryHelper.getClassLoadingMXBean());
                }
            }),
    
        /**
         * Compilation system of the Java virtual machine.
         */
        COMPILATION(
            "java.lang.management.CompilationMXBean",
            "java.lang", "Compilation", defaultKeyProperties(),
            true, // singleton
            new MXBeanFetcher<CompilationMXBean>() { 
                public List<CompilationMXBean> getMXBeans() { 
                    CompilationMXBean m = ManagementFactoryHelper.getCompilationMXBean();
                    if (m == null) { 
                       return Collections.emptyList();
                    } else { 
                       return Collections.singletonList(m);
                    }
                }
            }),
    	.....
    	}

### MBeanServerFactory.createMBeanServer() ###

public static MBeanServer createMBeanServer() { 
            return createMBeanServer(null);
        }
    	 public static MBeanServer createMBeanServer(String domain)  { 
    		checkPermission("createMBeanServer");
    
    		final MBeanServer mBeanServer = newMBeanServer(domain);
    		addMBeanServer(mBeanServer);
    		return mBeanServer;
    	}
    	public static MBeanServer newMBeanServer(String domain)  { 
            checkPermission("newMBeanServer");
    
            // Get the builder. Creates a new one if necessary.
            //
            final MBeanServerBuilder mbsBuilder = getNewMBeanServerBuilder();
            // Returned value cannot be null.  NullPointerException if violated.
    
            synchronized(mbsBuilder) { 
                final MBeanServerDelegate delegate  =
                        mbsBuilder.newMBeanServerDelegate();
                if (delegate == null) { 
                    final String msg =
                            "MBeanServerBuilder.newMBeanServerDelegate() " +
                            "returned null";
                    throw new JMRuntimeException(msg);
                }
                final MBeanServer mbeanServer =
                        mbsBuilder.newMBeanServer(domain,null,delegate);
                if (mbeanServer == null) { 
                    final String msg =
                            "MBeanServerBuilder.newMBeanServer() returned null";
                    throw new JMRuntimeException(msg);
                }
                return mbeanServer;
            }
        }

createMBeanServer方法会调用newMBeanServer方法实例化MBeanServer  
newMBeanServer方法中会先使用MBeanServerBuilder.newMBeanServerDelegate()实例化一个MBeanServerBuilder  
再使用MBeanServerBuilder.newMBeanServer(domain,null,delegate)方法实例化一个MBeanServer

public MBeanServer newMBeanServer(String  defaultDomain,
                                          MBeanServer  outer,
                                          MBeanServerDelegate delegate) { 
            // By default, MBeanServerInterceptors are disabled.
            // Use com.sun.jmx.mbeanserver.MBeanServerBuilder to obtain
            // MBeanServers on which MBeanServerInterceptors are enabled.
            return JmxMBeanServer.newMBeanServer(defaultDomain,outer,delegate,
                                                 false);
        }

newMBeanServer方法实际实例化并返回的是一个JmxMBeanServer对象

//in JmxMBeanServer
        public static MBeanServer newMBeanServer(String defaultDomain,
                                                 MBeanServer outer,
                                                 MBeanServerDelegate delegate,
                                                 boolean interceptors) { 
            // Determine whether to use fair locking for the repository.
            // Default is true.
            final boolean fairLock = DEFAULT_FAIR_LOCK_POLICY;
    
            checkNewMBeanServerPermission();
    
            // This constructor happens to disregard the value of the interceptors
            // flag - that is, it always uses the default value - false.
            // This is admitedly a bug, but we chose not to fix it for now
            // since we would rather not have anybody depending on the Sun private
            // interceptor APIs - which is most probably going to be removed and
            // replaced by a public (javax) feature in the future.
            //
            return new JmxMBeanServer(defaultDomain,outer,delegate,null,
                                      interceptors,fairLock);
        }
    	
    	JmxMBeanServer(String domain, MBeanServer outer,
                       MBeanServerDelegate    delegate,
                       MBeanInstantiator      instantiator,
                       boolean                interceptors,
                       boolean                fairLock)  { 
    
            if (instantiator == null) { 
                final ModifiableClassLoaderRepository
                    clr = new ClassLoaderRepositorySupport();
                instantiator = new MBeanInstantiator(clr);
            }
    
            final MBeanInstantiator fInstantiator = instantiator;
            this.secureClr = new
                SecureClassLoaderRepository(AccessController.doPrivileged(new PrivilegedAction<ClassLoaderRepository>() { 
                    @Override
                    public ClassLoaderRepository run() { 
                        return fInstantiator.getClassLoaderRepository();
                    }
                })
            );
            if (delegate == null)
                delegate = new MBeanServerDelegateImpl();
            if (outer == null)
                outer = this;
    
            this.instantiator = instantiator;
            this.mBeanServerDelegateObject = delegate;
            this.outerShell   = outer;
    
            final Repository repository = new Repository(domain);
            this.mbsInterceptor =
                new DefaultMBeanServerInterceptor(outer, delegate, instantiator,
                                                  repository);
            this.interceptorsEnabled = interceptors;
            initialize();
        }

实例化一个Repository并聚合到新生成的一个DefaultMBeanServerInterceptor  
Repository就是MBeanServer存放MBean的容器类，其内部维护一个Map<String,Map<String,NamedObject>> domainTb的成员  
此处由于是第一次实例化MBeanServer，传入的domain为null，最终会使用ServiceName的静态的成员值DefaultDomain作为默认域

public class ServiceName { 
    
        /**
         * The default domain.
         * <BR>
         * The value is <CODE>DefaultDomain</CODE>.
         */
        public static final String DOMAIN = "DefaultDomain";
    	.....
    }

NamedObject类是聚合ObjectName和DynamicMBean的辅助类

public class NamedObject  { 
    
    
        /**
         * Object name.
         */
        private final ObjectName name;
    
        /**
         * Object reference.
         */
        private final DynamicMBean object;
    	.....
    }

后续的注册bean和获取bean等方法实现最终都是由mbsInterceptor成员去操作

### LocateRegistry.createRegistry ###

创建注册中心并开启端口监听，返回创建的RegistryImpl实例  
源码分析请参照本人的另一篇博客——java-rmi源码解析[java-rmi源码解析][java-rmi]

### MBeanServer.registerMBean ###

在JmxMBeanServer中的实现

上面讲到，默认的MBeanServer的mbsInterceptor成员由new DefaultMBeanServerInterceptor(outer, delegate, instantiator,repository)实例化

public ObjectInstance registerMBean(Object object, ObjectName name)
            throws InstanceAlreadyExistsException, MBeanRegistrationException,
            NotCompliantMBeanException  { 
    
            // ------------------------------
            // ------------------------------
            Class<?> theClass = object.getClass();
    
            Introspector.checkCompliance(theClass);
    
            final String infoClassName = getNewMBeanClassName(object);
    
            checkMBeanPermission(infoClassName, null, name, "registerMBean");
            checkMBeanTrustPermission(theClass);
    
            return registerObject(infoClassName, object, name);
        }
    	private ObjectInstance registerObject(String classname,
                                              Object object, ObjectName name)
            throws InstanceAlreadyExistsException,
                   MBeanRegistrationException,
                   NotCompliantMBeanException { 
    
            if (object == null) { 
                final RuntimeException wrapped =
                    new IllegalArgumentException("Cannot add null object");
                throw new RuntimeOperationsException(wrapped,
                            "Exception occurred trying to register the MBean");
            }
    
            DynamicMBean mbean = Introspector.makeDynamicMBean(object);
    
            return registerDynamicMBean(classname, mbean, name);
        }

DefaultMBeanServerInterceptor会将要注册的MBean封装为DynamicMBean，调用registerDynamicMBean进行注册

private ObjectInstance registerDynamicMBean(String classname,
                                                    DynamicMBean mbean,
                                                    ObjectName name)
            throws InstanceAlreadyExistsException,
                   MBeanRegistrationException,
                   NotCompliantMBeanException { 
    
    
            name = nonDefaultDomain(name);
    
            if (MBEANSERVER_LOGGER.isLoggable(Level.FINER)) { 
                MBEANSERVER_LOGGER.logp(Level.FINER,
                        DefaultMBeanServerInterceptor.class.getName(),
                        "registerMBean", "ObjectName = " + name);
            }
    
            ObjectName logicalName = preRegister(mbean, server, name);
    
            // preRegister returned successfully, so from this point on we
            // must call postRegister(false) if there is any problem.
            boolean registered = false;
            boolean registerFailed = false;
            ResourceContext context = null;
    
            try { 
                if (mbean instanceof DynamicMBean2) { 
                    try { 
                        ((DynamicMBean2) mbean).preRegister2(server, logicalName); registerFailed = true; // until we succeed } catch (Exception e) { if (e instanceof RuntimeException) throw (RuntimeException) e; if (e instanceof InstanceAlreadyExistsException) throw (InstanceAlreadyExistsException) e; throw new RuntimeException(e); } } if (logicalName != name && logicalName != null) { logicalName = ObjectName.getInstance(nonDefaultDomain(logicalName));
                }
    
                checkMBeanPermission(classname, null, logicalName, "registerMBean");
    
                if (logicalName == null) { 
                    final RuntimeException wrapped =
                        new IllegalArgumentException("No object name specified");
                    throw new RuntimeOperationsException(wrapped,
                                "Exception occurred trying to register the MBean");
                }
    
                final Object resource = getResource(mbean);
    
                // Register the MBean with the repository.
                // Returns the resource context that was used.
                // The returned context does nothing for regular MBeans.
                // For ClassLoader MBeans the context makes it possible to register these
                // objects with the appropriate framework artifacts, such as
                // the CLR, from within the repository lock.
                // In case of success, we also need to call context.done() at the
                // end of this method.
                //
                context = registerWithRepository(resource, mbean, logicalName);
    
    
                registerFailed = false;
                registered = true;
    
            } finally { 
                try { 
                    postRegister(logicalName, mbean, registered, registerFailed);
                } finally { 
                    if (registered && context!=null) context.done();
                }
            }
            return new ObjectInstance(logicalName, classname);
        }

registerDynamicMBean方法最终调用registerWithRepository方法将DynamicMBean对象注册到Repository里

private ResourceContext registerWithRepository(
                final Object resource,
                final DynamicMBean object,
                final ObjectName logicalName)
                throws InstanceAlreadyExistsException,
                MBeanRegistrationException { 
    
            // Creates a registration context, if needed.
            //
            final ResourceContext context =
                    makeResourceContextFor(resource, logicalName);
    
    
            repository.addMBean(object, logicalName, context);
            // May throw InstanceAlreadyExistsException
    
            // ---------------------
            // Send create event
            // ---------------------
            if (MBEANSERVER_LOGGER.isLoggable(Level.FINER)) { 
                MBEANSERVER_LOGGER.logp(Level.FINER,
                        DefaultMBeanServerInterceptor.class.getName(),
                        "addObject", "Send create notification of object " +
                        logicalName.getCanonicalName());
            }
    
            sendNotification(
                    MBeanServerNotification.REGISTRATION_NOTIFICATION,
                    logicalName);
    
            return context;
        }

前面已经讲过在创建DefaultMBeanServerInterceptor实例时，会实例化一个repository对象并装载到成员  
注册bean会调用repository的addMBean方法

public void addMBean(final DynamicMBean object, ObjectName name,
                final RegistrationContext context)
            throws InstanceAlreadyExistsException { 
    
            if (MBEANSERVER_LOGGER.isLoggable(Level.FINER)) { 
                MBEANSERVER_LOGGER.logp(Level.FINER, Repository.class.getName(),
                        "addMBean", "name = " + name);
            }
    
            // Extract the domain name.
            String dom = name.getDomain().intern();
            boolean to_default_domain = false;
    
            // Set domain to default if domain is empty and not already set
            if (dom.length() == 0)
                name = Util.newObjectName(domain + name.toString());
    
            // Do we have default domain ?
            if (dom == domain) {   // ES: OK (dom & domain are interned)
                to_default_domain = true;
                dom = domain;
            } else { 
                to_default_domain = false;
            }
    
            // Validate name for an object
            if (name.isPattern()) { 
                throw new RuntimeOperationsException(
                 new IllegalArgumentException("Repository: cannot add mbean for " +
                                              "pattern name " + name.toString()));
            }
    
            lock.writeLock().lock();
            try { 
                // Domain cannot be JMImplementation if entry does not exist
                if ( !to_default_domain &&
                        dom.equals("JMImplementation") &&
                        domainTb.containsKey("JMImplementation")) { 
                    throw new RuntimeOperationsException(
                            new IllegalArgumentException(
                            "Repository: domain name cannot be JMImplementation"));
                }
    
                // If domain does not already exist, add it to the hash table
                final Map<String,NamedObject> moiTb = domainTb.get(dom);
                if (moiTb == null) { 
                    addNewDomMoi(object, dom, name, context);
                    return;
                } else { 
                    // Add instance if not already present
                    String cstr = name.getCanonicalKeyPropertyListString();
                    NamedObject elmt= moiTb.get(cstr);
                    if (elmt != null) { 
                        throw new InstanceAlreadyExistsException(name.toString());
                    } else { 
                        nbElements++;
                        addMoiToTb(object,name,cstr,moiTb,context);
                    }
                }
    
            } finally { 
                lock.writeLock().unlock();
            }
        }
    	private void addMoiToTb(final DynamicMBean object,
                final ObjectName name,
                final String key,
                final Map<String,NamedObject> moiTb,
                final RegistrationContext context) { 
            registering(context);
            moiTb.put(key,new NamedObject(name, object));
        }

domainTb成员就是前面说过的repository中存储MBean的Map，类型是Map<String,Map<String,NamedObject>>  
add方法里会通过writelock进行同步  
如果获取到的moiTb，代表该MBean的域名尚未加入domainTb，会将域名加入map并将MBean也加入

## JmxMBeanServer ##

JmxMBeanServer  
不提供直接返回MBean对象的方法  
但提供了很多行为如 setAttributes，getAttribute，invoke等方法，根据ObjectName参数进行MBean识别  
调用成员的DefaultMBeanServerInterceptor实例去执行对应的修改属性，获取属性值，执行方法等行为  
DefaultMBeanServerInterceptor最终是获取repository中的MBean去执行对应行为  
通过getObjectInstance可以获得该MBean的类名和域名信息的封装对象

public ObjectInstance getObjectInstance(ObjectName name)
            throws InstanceNotFoundException { 
    
            return mbsInterceptor.getObjectInstance(cloneObjectName(name));
        }
    	public Object getAttribute(ObjectName name, String attribute)
            throws MBeanException, AttributeNotFoundException,
                   InstanceNotFoundException, ReflectionException { 
    
            return mbsInterceptor.getAttribute(cloneObjectName(name), attribute);
        }
    	public void setAttribute(ObjectName name, Attribute attribute)
            throws InstanceNotFoundException, AttributeNotFoundException,
                   InvalidAttributeValueException, MBeanException,
                   ReflectionException  { 
    
            mbsInterceptor.setAttribute(cloneObjectName(name),
                                        cloneAttribute(attribute));
        }
    	public Object invoke(ObjectName name, String operationName,
                             Object params[], String signature[])
            throws InstanceNotFoundException, MBeanException,
                   ReflectionException { 
            return mbsInterceptor.invoke(cloneObjectName(name), operationName,
                                         params, signature);
        }

## JMXConnectorServerFactory.newJMXConnectorServer ##

该方法创建一个JMXConnectorServer，将MBeanServer和JMXServiceURL传递过去  
最终url、MbeanServer等对象会被聚合到JMXConnectorServer，作为成员

public static JMXConnectorServer
            newJMXConnectorServer(JMXServiceURL serviceURL,
                                  Map<String,?> environment,
                                  MBeanServer mbeanServer)
                throws IOException { 
            Map<String, Object> envcopy;
            if (environment == null)
                envcopy = new HashMap<String, Object>();
            else { 
                EnvHelp.checkAttributes(environment);
                envcopy = new HashMap<String, Object>(environment);
            }
    
            final Class<JMXConnectorServerProvider> targetInterface =
                    JMXConnectorServerProvider.class;
            final ClassLoader loader =
                JMXConnectorFactory.resolveClassLoader(envcopy);
            final String protocol = serviceURL.getProtocol();
            final String providerClassName = "ServerProvider";
    
            JMXConnectorServerProvider provider =
                JMXConnectorFactory.getProvider(serviceURL,
                                                envcopy,
                                                providerClassName,
                                                targetInterface,
                                                loader);
    
            IOException exception = null;
            if (provider == null) { 
                // Loader is null when context class loader is set to null
                // and no loader has been provided in map.
                // com.sun.jmx.remote.util.Service class extracted from j2se
                // provider search algorithm doesn't handle well null classloader.
                if (loader != null) { 
                    try { 
                        JMXConnectorServer connection =
                            getConnectorServerAsService(loader,
                                                        serviceURL,
                                                        envcopy,
                                                        mbeanServer);
                        if (connection != null)
                            return connection;
                    } catch (JMXProviderException e) { 
                        throw e;
                    } catch (IOException e) { 
                        exception = e;
                    }
                }
                provider =
                    JMXConnectorFactory.getProvider(
                        protocol,
                        PROTOCOL_PROVIDER_DEFAULT_PACKAGE,
                        JMXConnectorFactory.class.getClassLoader(),
                        providerClassName,
                        targetInterface);
            }
    
            if (provider == null) { 
                MalformedURLException e =
                    new MalformedURLException("Unsupported protocol: " + protocol);
                if (exception == null) { 
                    throw e;
                } else { 
                    throw EnvHelp.initCause(e, exception);
                }
            }
    
            envcopy = Collections.unmodifiableMap(envcopy);
    
            return provider.newJMXConnectorServer(serviceURL,
                                                  envcopy,
                                                  mbeanServer);
        }

JMXConnectorServerFactory的newJMXConnectorServer最终是返回由provider生产的JMXConnectorServer  
provider是接口，在jdk里对于该方法有两个实现类，一个是返回基于rmi协议，另一个是返回基于iiop协议的

//ServiceProvider for rmi
    	public JMXConnectorServer newJMXConnectorServer(JMXServiceURL serviceURL,
                                                        Map<String,?> environment,
                                                        MBeanServer mbeanServer)
                throws IOException { 
            if (!serviceURL.getProtocol().equals("rmi")) { 
                throw new MalformedURLException("Protocol not rmi: " +
                                                serviceURL.getProtocol());
            }
            return new RMIConnectorServer(serviceURL, environment, mbeanServer);
        }

需要留意的是，在serviceProvider中调用生成RMIConnectorServer时，最终会调用传递(RMIServerImpl) null为形参参数的构造函数构造  
也就是生成的RMIConnectorServer中是没有指定服务端对象的  
RMIServerImpl会在JMXConnectorServer调用start方法后结合前面聚合到JMXConnectorServer中的rmi的url去实例化

public RMIConnectorServer(JMXServiceURL url, Map<String,?> environment,
                                  MBeanServer mbeanServer)
                throws IOException { 
            this(url, environment, (RMIServerImpl) null, mbeanServer);
        }
    	public RMIConnectorServer(JMXServiceURL url, Map<String,?> environment,
                                  RMIServerImpl rmiServerImpl,
                                  MBeanServer mbeanServer)
                throws IOException { 
            super(mbeanServer);
    
            if (url == null) throw new
                IllegalArgumentException("Null JMXServiceURL");
            if (rmiServerImpl == null) { 
                final String prt = url.getProtocol();
                if (prt == null || !(prt.equals("rmi") || prt.equals("iiop"))) { 
                    final String msg = "Invalid protocol type: " + prt;
                    throw new MalformedURLException(msg);
                }
                final String urlPath = url.getURLPath();
                if (!urlPath.equals("")
                    && !urlPath.equals("/")
                    && !urlPath.startsWith("/jndi/")) { 
                    final String msg = "URL path must be empty or start with " +
                        "/jndi/";
                    throw new MalformedURLException(msg);
                }
            }
    
            if (environment == null)
                this.attributes = Collections.emptyMap();
            else { 
                EnvHelp.checkAttributes(environment);
                this.attributes = Collections.unmodifiableMap(environment);
            }
    
            this.address = url;
            this.rmiServerImpl = rmiServerImpl;
        }

## jmxConnectorServer.start() ##

启动JMX链接服务器，该过程会完成rmiServerImpl的实例化（开启监听rmi服务端口）  
所以如果前面没有调用LocateRegistry.createRegistry(rmiPort)对端口进行注册，会导致报错

public synchronized void start() throws IOException { 
            final boolean tracing = logger.traceOn();
    
            if (state == STARTED) { 
                if (tracing) logger.trace("start", "already started");
                return;
            } else if (state == STOPPED) { 
                if (tracing) logger.trace("start", "already stopped");
                throw new IOException("The server has been stopped.");
            }
    
            if (getMBeanServer() == null)
                throw new IllegalStateException("This connector server is not " +
                                                "attached to an MBean server");
    
            // Check the internal access file property to see
            // if an MBeanServerForwarder is to be provided
            //
            if (attributes != null) { 
                // Check if access file property is specified
                //
                String accessFile =
                    (String) attributes.get("jmx.remote.x.access.file");
                if (accessFile != null) { 
                    // Access file property specified, create an instance
                    // of the MBeanServerFileAccessController class
                    //
                    MBeanServerForwarder mbsf;
                    try { 
                        mbsf = new MBeanServerFileAccessController(accessFile);
                    } catch (IOException e) { 
                        throw EnvHelp.initCause(
                            new IllegalArgumentException(e.getMessage()), e);
                    }
                    // Set the MBeanServerForwarder
                    //
                    setMBeanServerForwarder(mbsf);
                }
            }
    
            try { 
                if (tracing) logger.trace("start", "setting default class loader");
                defaultClassLoader = EnvHelp.resolveServerClassLoader(
                        attributes, getMBeanServer());
            } catch (InstanceNotFoundException infc) { 
                IllegalArgumentException x = new
                    IllegalArgumentException("ClassLoader not found: "+infc);
                throw EnvHelp.initCause(x,infc);
            }
    
            if (tracing) logger.trace("start", "setting RMIServer object");
            final RMIServerImpl rmiServer;
    
            if (rmiServerImpl != null)
                rmiServer = rmiServerImpl;
            else
                rmiServer = newServer();
    
            rmiServer.setMBeanServer(getMBeanServer());
            rmiServer.setDefaultClassLoader(defaultClassLoader);
            rmiServer.setRMIConnectorServer(this);
            rmiServer.export();
    
            try { 
                if (tracing) logger.trace("start", "getting RMIServer object to export");
                final RMIServer objref = objectToBind(rmiServer, attributes);
    
                if (address != null && address.getURLPath().startsWith("/jndi/")) { 
                    final String jndiUrl = address.getURLPath().substring(6);
    
                    if (tracing)
                        logger.trace("start", "Using external directory: " + jndiUrl);
    
                    String stringBoolean = (String) attributes.get(JNDI_REBIND_ATTRIBUTE);
                    final boolean rebind = EnvHelp.computeBooleanFromString( stringBoolean );
    
                    if (tracing)
                        logger.trace("start", JNDI_REBIND_ATTRIBUTE + "=" + rebind);
    
                    try { 
                        if (tracing) logger.trace("start", "binding to " + jndiUrl);
    
                        final Hashtable<?, ?> usemap = EnvHelp.mapToHashtable(attributes);
    
                        bind(jndiUrl, usemap, objref, rebind);
    
                        boundJndiUrl = jndiUrl;
                    } catch (NamingException e) { 
                        // fit e in the nested exception if we are on 1.4
                        throw newIOException("Cannot bind to URL ["+jndiUrl+"]: "
                                             + e, e);
                    }
                } else { 
                    // if jndiURL is null, we must encode the stub into the URL.
                    if (tracing) logger.trace("start", "Encoding URL");
    
                    encodeStubInAddress(objref, attributes);
    
                    if (tracing) logger.trace("start", "Encoded URL: " + this.address);
                }
            } catch (Exception e) { 
                try { 
                    rmiServer.close();
                } catch (Exception x) { 
                    // OK: we are already throwing another exception
                }
                if (e instanceof RuntimeException)
                    throw (RuntimeException) e;
                else if (e instanceof IOException)
                    throw (IOException) e;
                else
                    throw newIOException("Got unexpected exception while " +
                                         "starting the connector server: "
                                         + e, e);
            }
    
            rmiServerImpl = rmiServer;
    
            synchronized(openedServers) { 
                openedServers.add(this);
            }
    
            state = STARTED;
    
            if (tracing) { 
                logger.trace("start", "Connector Server Address = " + address);
                logger.trace("start", "started.");
            }
        }

前面讲过rmiServerImpl成员是空的，所以这时会调用newServer方法进行创建

RMIServerImpl newServer() throws IOException { 
            final boolean iiop = isIiopURL(address,true);
            final int port;
            if (address == null)
                port = 0;
            else
                port = address.getPort();
            if (iiop)
                return newIIOPServer(attributes);
            else
                return newJRMPServer(attributes, port);
        }

接下来会调用objectToBind  
通过toStub方法创建当前的RMIServer对象的远程代理对象

private static RMIServer objectToBind(
                RMIServerImpl rmiServer, Map<String, ?> env)
            throws IOException { 
            return RMIConnector.
                connectStub((RMIServer)rmiServer.toStub(),env); } public Remote toStub() throws IOException { return RemoteObject.toStub(this); } public static Remote toStub(Remote obj) throws NoSuchObjectException { if (obj instanceof RemoteStub || (obj != null && Proxy.isProxyClass(obj.getClass()) &&
                 Proxy.getInvocationHandler(obj) instanceof
                 RemoteObjectInvocationHandler))
            { 
                return obj;
            } else { 
                return sun.rmi.transport.ObjectTable.getStub(obj);
            }
        }

然后调用bind方法将RMIServer的远程代理对象注册到注册中心

void bind(String jndiUrl, Hashtable<?, ?> attributes,
                  RMIServer rmiServer, boolean rebind)
            throws NamingException, MalformedURLException { 
            // if jndiURL is not null, we nust bind the stub to a
            // directory.
            InitialContext ctx =
                new InitialContext(attributes);
    
            if (rebind)
                ctx.rebind(jndiUrl, rmiServer);
            else
                ctx.bind(jndiUrl, rmiServer);
            ctx.close();
        }

至此，完成了JmxConnectorServer的启动，程序可以通过jmx规范，访问MBeanServer与其上的MBean  
关于remote和rmi的细节可以参考本人另一篇博客——java-rmi源码解析[java-rmi源码解析][java-rmi]

更多文章，请搜索公众号歪歪梯Club  
![更多资料，请搜索公众号编程宝可梦][20200521183346518.jpg]

[jconsole]: /images/20211211/a4b1305dd296467f991d8fa704f3b1a8.png
[jconsole 1]: /images/20211211/4ae1fc99a3e74d3e94434459d19a7160.png
[jconsole 2]: /images/20211211/907d6e93967e460baef1e282c1ddd20e.png
[java-rmi]: https://blog.csdn.net/weixin_44627989/article/details/93055791
[20200521183346518.jpg]: /images/20211211/ac11bc33d9c8412697cc849077d49b66.png