动态MBean：DynamicMBean

JMX的Dynamic MBean不需要自定义MBean接口，只需要实现JDK提供的DynamicMBean接口即可。Dynamic MBean没有任何明显写在代码里的属性和方法，所有的属性和方法都是通过反射结合JMX提供的辅助元数据，从而动态生成的。

Dynamic MBean：

[java] view plain copy    package com.jmx.dynamic.demo;            import java.lang.reflect.Constructor;      import java.util.Iterator;            import javax.management.Attribute;      import javax.management.AttributeList;      import javax.management.DynamicMBean;      import javax.management.MBeanAttributeInfo;      import javax.management.MBeanConstructorInfo;      import javax.management.MBeanException;      import javax.management.MBeanInfo;      import javax.management.MBeanNotificationInfo;      import javax.management.MBeanOperationInfo;      import javax.management.MBeanParameterInfo;      import javax.management.ReflectionException;            public class HelloDynamic implements DynamicMBean {                    //attributes          private String name;              private MBeanInfo mBeanInfo = null;             private String className;             private String description;             private MBeanAttributeInfo[] attributes;             private MBeanConstructorInfo[] constructors;             private MBeanOperationInfo[] operations;             MBeanNotificationInfo[] mBeanNotificationInfoArray;                 public HelloDynamic() {                 init();                 buildDynamicMBean();             }                   private void init() {                 className = this.getClass().getName();                 description = "Simple implementation of a MBean.";                               //initial attributes              attributes = new MBeanAttributeInfo[1];                 //initial constructors              constructors = new MBeanConstructorInfo[1];              //initial method              operations = new MBeanOperationInfo[1];                               mBeanNotificationInfoArray = new MBeanNotificationInfo[0];             }                    private void buildDynamicMBean() {                 //create constructor                 Constructor[] thisconstructors = this.getClass().getConstructors();                 constructors[0] = new MBeanConstructorInfo("HelloDynamic(): Constructs a HelloDynamic object", thisconstructors[0]);                               //create attribute                 attributes[0] = new MBeanAttributeInfo("Name", "java.lang.String", "Name: name string.", true, true,false);                               //create operate method              MBeanParameterInfo[] params = null;//no parameter              operations[0] = new MBeanOperationInfo("print", "print(): print the name", params, "void", MBeanOperationInfo.INFO);                                //create mbean              mBeanInfo = new MBeanInfo(className, description, attributes, constructors, operations, mBeanNotificationInfoArray);             }                       //dynamically add a print1 method          private void dynamicAddOperation() {                 init();                 operations = new MBeanOperationInfo[2];              buildDynamicMBean();                 operations[1] = new MBeanOperationInfo("print1", "print1(): print the name", null, "void", MBeanOperationInfo.INFO);                 mBeanInfo = new MBeanInfo(className, description, attributes, constructors, operations, mBeanNotificationInfoArray);             }                       @Override          public Object getAttribute(String attribute_name) {              if (attribute_name == null) {                  return null;              }                            if (attribute_name.equals("Name")) {                  return name;              }                            return null;          }                   @Override          public void setAttribute(Attribute attribute) {               if (attribute == null) {                  return;              }                            String Name = attribute.getName();                 Object value = attribute.getValue();                 try {                     if (Name.equals("Name")) {                      // if null value, try and if the setter returns any exception                         if (value == null) {                             name = null;                         // if non null value, make sure it is assignable to the attribute                         } else if ((Class.forName("java.lang.String")).isAssignableFrom(value.getClass())) {                              name = (String) value;                         }                     }                 } catch (Exception e) {                     e.printStackTrace();                 }             }                   @Override          public AttributeList getAttributes(String[] attributeNames) {                 if (attributeNames == null) {                  return null;              }                            AttributeList resultList = new AttributeList();                 // if attributeNames is empty, return anempty result list                 if (attributeNames.length == 0) {                  return resultList;              }                            for (int i = 0; i < attributeNames.length; i++) {                     try {                         Object value = getAttribute(attributeNames[i]);                         resultList.add(new Attribute(attributeNames[i], value));                     } catch (Exception e) {                         e.printStackTrace();                     }                 }                 return resultList;             }                   @Override          public AttributeList setAttributes(AttributeList attributes) {                 if (attributes == null) {                  return null;              }                                AttributeList resultList = new AttributeList();                 // if attributeNames is empty, nothing more to do                 if (attributes.isEmpty()) {                  return resultList;              }                            // for each attribute, try to set it and add to the result list if successfull                 for (Iterator i = attributes.iterator(); i.hasNext();) {                     Attribute attr = (Attribute) i.next();                     try {                      setAttribute(attr);                         String name = attr.getName();                         Object value = getAttribute(name);                         resultList.add(new Attribute(name, value));                     } catch (Exception e) {                         e.printStackTrace();                     }                 }                     return resultList;                 }                       @Override          public Object invoke(String operationName, Object params[], String signature[]) throws MBeanException,ReflectionException {                 // Check for a recognized operationname and call the corresponding operation                 if (operationName.equals("print")) {                   System.out.println("Hello, " + name + ", this is HelloDynamic!");                                      //dynamic add a method                  dynamicAddOperation();                     return null;                 } else if (operationName.equals("print1")) {                     System.out.println("dynamically add a print1 method");                     return null;                 } else {                     // unrecognized operation name:                  throw new ReflectionException(new NoSuchMethodException(operationName), "Cannot find the operation " + operationName + " in " + className);                 }                   }                   public MBeanInfo getMBeanInfo() {                 return mBeanInfo;             }      }  

通过Agent调用Dynamic MBean，方式和Standard MBean相同

[java] view plain copy    package com.jmx.dynamic.demo;            import java.lang.management.ManagementFactory;            import javax.management.InstanceAlreadyExistsException;      import javax.management.MBeanRegistrationException;      import javax.management.MBeanServer;      import javax.management.MalformedObjectNameException;      import javax.management.NotCompliantMBeanException;      import javax.management.ObjectName;            import com.sun.jdmk.comm.HtmlAdaptorServer;            public class HelloAgent {//as same as standard mbean          public static void main(String[] args) throws MalformedObjectNameException, NullPointerException, InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {                            //create mbean server              MBeanServer server = ManagementFactory.getPlatformMBeanServer();                            //create object name              ObjectName helloName = new ObjectName("jmx:name=dynamicBeanHello");                            //create mbean and register mbean              server.registerMBean(new HelloDynamic(), helloName);                            //create adaptor, adaptor is just a form as show mbean. It has no relation to specific mbean.              HtmlAdaptorServer adaptor  = new HtmlAdaptorServer();              //create adaptor name              ObjectName adaptorName = new ObjectName("jmxAdaptor:name=adaptor,port=5050");              //register adaptor and adaptor name              server.registerMBean(adaptor, adaptorName);                            adaptor.setPort(9999);              adaptor.start();              System.out.println("....................jmx server start....................");          }      }  

启动JMX服务，访问http://localhost:9999/

点击我们在JMXServer上注册的Dynamic MBean

可以看到动态生成的属性和方法：

点击print方法后，控制台输出如下：

再返回MBean View，可以看到又动态创建了一个print1方法：

Dynamic MBean应用的场景并不多，正所谓：利器深藏之而不用，非常时方现光芒。