从零开始玩转JMX(四)——Apache Commons Modeler Dynamic MBean

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欢迎跳转到本文的原文链接：https://honeypps.com/java/jmx-quick-start-4-dynamic-mbean/

Apache Commons Modeler

前面的Model MBean的创建方式看上去特别复杂，一个简单功能的类ModelMBeanUtils 写了很多代码，那有木有简单点的方式呢，答案是肯定的，这里就引出了Apache Commons Modeler（使用这个需要在classpath中导入commons-modeler-2.0.1.jar以及modeler的依赖项目commons-logging-1.1.3.jar，下载地址：http://commons.apache.org/proper/commons-modeler/download_modeler.cgi），使用Apache的Moleler库创建Model MBean最大帮助是，我们不需要再写复杂的代码来创建ModelMBeanInfo对象了。只需要一个MBean描述符（实际上就是一个xml配置文件，Apache Commons Modeler将ModelMBeanUtils 复杂的创建过程转移到xml中来配置，然后自身模块创建对象代替ModelMBeanUtils 的功能，简化用户的操作）来对Model MBean进行描述，就可以轻松的创建Model MBean.

下面来讲前面的Hello.java和HelloAgent.java的例子采用Apache Commons Modele进行改造。

首先还是Hello.java，和Model MBean中的一样，没有implements任何接口。

package com.test.jmx.modeler;public class Hello{private String name;public String getName() {return name;}public void setName(String name) {this.name= name;}public void printHello() {System.out.println("Hello World, "+name);}public void printHello(String whoName) {System.out.println("Hello, "+whoName);}
}

接下去就是最关键的描述文件(mbeans-descriptors.xml)了：

<?xml version="1.0" encoding="UTF-8" ?>
<mbeans-descriptors><mbean name="Hello" description="the hello bean" domain="MyMBean" group="helloGroup" type="com.test.jmx.modeler.Hello"><attribute name="name" description="a name attribute" type="java.lang.String" writeable="true"/><operation name="printHello" description="public void printHello()" impact="ACTION" returnType="void"/><operation name="printHello" description="public void printHello(String whoName)" impact="ACTION" returnType="void"><parameter name="whoName" description="method parameter of printHello" type="java.lang.String"></parameter> </operation></mbean>
</mbeans-descriptors>

描述文件的名字可以随意，最主要的是要和下面的HelloAgent.java对应起来。
通过这个xml文件的定义就描述了Model MBean所需要的metadata信息和一个基本的ModelMBean实现。
关于这个xml文件有几个需要说明的地方：

<mbean>的属性classname,name,type:

name属性是每个MBean被Registry对象注册的对象名
type属性是真正被管理资源的全面（包括包名）
classname属性是用户扩展的用于实现代理功能的Model MBean的全名，如果不提供Modeler会使用BaseModelMBean；如果提供了代理的ModelMBean对象，在使用时可以使用如下的代码样本访问他所代理的资源对象。

其余的标签就比较好理解了。综述：上面所示代码声明了一个Model MBean, 唯一标示是“Hello”,该MBean负责管理的对象是com.test.jmx.modeler.Hello的实例。域是MyMBean。这个MBean暴露了一个属性name和两个方法printHello()和printHello(String whoName).

下面是新的HelloAgent.java的代码：

package com.test.jmx.modeler;import com.sun.jdmk.comm.HtmlAdaptorServer;
import org.apache.commons.modeler.ManagedBean;
import org.apache.commons.modeler.Registry;import javax.management.MBeanServer;
import javax.management.ObjectName;
import javax.management.modelmbean.ModelMBean;
import java.io.InputStream;public class HelloAgent  {public static void main(String[] args) throws Exception {
// 需要将xml信息读入到Registry对象中Registry registry = Registry.getRegistry(null,null);InputStream stream = HelloAgent.class.getResourceAsStream("mbeans-descriptors.xml");registry.loadMetadata(stream);MBeanServer server = registry.getMBeanServer();// 之前是：MBeanServer server = ManagementFactory.getPlatformMBeanServer();ManagedBean managed = registry.findManagedBean("Hello");ObjectName helloName = new ObjectName(managed.getDomain()+":name=HelloWorld");
// 以前是Hello hello = new Hello(); 为什么要多个createMBean？因为现在的写法没有写MBean,所以才要动态生成一个，以前就直接
// 把new hello()注册到MBeanServer就可以了，server会自动找到它的HelloMBean接口文件。ModelMBean hello = managed.createMBean(new Hello());server.registerMBean(hello,helloName);ObjectName adapterName = new ObjectName(managed.getDomain()+":name = htmladapter,port=8082");HtmlAdaptorServer adapter = new HtmlAdaptorServer();server.registerMBean(adapter,adapterName);adapter.start();}
}

注意这里的Registry是指org.apache.commons.modeler.Registry，因为JMX自身也有一个Registry(java.rmi.registry.Registry)。通过Modeler组件提供的Registry对象，可以很方便的完成MBeanServer的创建。
运行效果和之前的一样，这里就不赘述了，有兴趣的小伙伴可以试一下。

Dynamic MBean

四种类型的MBean，前面所讲的都是常用的，现在还剩两种Open MBean就不讲述了，这里简单记录下Dynamic MBean。
Dynamic MBean不需要自定义MBean接口，只需要实现DynamicMBean接口即可，Dynamic MBean没有任何明显些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。
下面的代码中首先定义了一个属性name和一个方法print,之后在管理界面（localhost:8082）中点击print之后生成一个print1的方法。
Dynamic MBean的代码如下：

package com.test.jmx.DynamicMBean;import javax.management.*;
import java.lang.reflect.Constructor;
import java.util.Iterator;/*** Created by hidden on 2016/10/9.*/
public class HelloDynamic implements DynamicMBean {private String name;private MBeanInfo mBeanInfo = null;private String className;private String description;private MBeanAttributeInfo[] attributes;private MBeanConstructorInfo[] constructors;private MBeanOperationInfo[] operations;MBeanNotificationInfo[] mBeanNotificationInfoArray;private void init(){className = this.getClass().getName();description = "Simple implementation of a dynamic MBean.";attributes = new MBeanAttributeInfo[1];constructors = new MBeanConstructorInfo[1];operations = new MBeanOperationInfo[1];mBeanNotificationInfoArray = new MBeanNotificationInfo[0];}private void buildDynamicMBean(){Constructor[] thisConstructors = this.getClass().getConstructors();constructors[0] = new MBeanConstructorInfo("HelloDynamic(): Constructs a HelloDynamic Object",thisConstructors[0]);attributes[0] = new MBeanAttributeInfo("name","java.lang.String","Name:name string.",true,true,false);MBeanParameterInfo[] params = null;operations[0] = new MBeanOperationInfo("print","print():print the name",params,"void",MBeanOperationInfo.INFO);mBeanInfo = new MBeanInfo(className,description,attributes,constructors,operations,mBeanNotificationInfoArray);}public HelloDynamic(){init();buildDynamicMBean();}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);}@Overridepublic Object getAttribute(String attribute) throws AttributeNotFoundException, MBeanException, ReflectionException {if (attribute == null) {return null;}if (attribute.equals("Name")) {return name;}return null;}@Overridepublic void setAttribute(Attribute attribute) throws AttributeNotFoundException, InvalidAttributeValueException, MBeanException, ReflectionException {if (attribute == null) {return;}String Name = attribute.getName();Object value = attribute.getValue();try {if (Name.equals("Name")) {if (value == null) {name=null;} else if (Class.forName("java.lang.String").isAssignableFrom(value.getClass())) {name = (String) name;}}} catch (ClassNotFoundException e) {e.printStackTrace();}}@Overridepublic AttributeList getAttributes(String[] attributes) {if (attributes == null) {return null;}AttributeList resultList = new AttributeList();
//        if (attributes.length == 0) {
//            return resultList;
//        }for(int i=0;i<attributes.length;i++){try {Object value = getAttribute(attributes[i]);resultList.add(new Attribute(attributes[i],value));} catch (AttributeNotFoundException e) {e.printStackTrace();} catch (MBeanException e) {e.printStackTrace();} catch (ReflectionException e) {e.printStackTrace();}}return resultList;}@Overridepublic AttributeList setAttributes(AttributeList attributes) {if (attributes == null) {return null;}AttributeList resultList = new AttributeList();if(attributes.isEmpty()){return resultList;}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 (AttributeNotFoundException e) {e.printStackTrace();} catch (InvalidAttributeValueException e) {e.printStackTrace();} catch (MBeanException e) {e.printStackTrace();} catch (ReflectionException e) {e.printStackTrace();}}return resultList;}@Overridepublic Object invoke(String actionName, Object[] params, String[] signature) throws MBeanException, ReflectionException {if(actionName.equals("print")){System.out.println("Hello, "+name+",this is HelloDynamic!");dynamicAddOperation();return null;}else if(actionName.equals("print1")){System.out.println("这是动态增加的一个方法print1");return null;}else {throw new ReflectionException(new NoSuchMethodException(actionName),"Cannot find the operation "+actionName+" in "+className);}}@Overridepublic MBeanInfo getMBeanInfo() {return mBeanInfo;}
}

通过Agent调用Dynamic MBean：

package com.test.jmx.DynamicMBean;import com.sun.jdmk.comm.HtmlAdaptorServer;import javax.management.*;
import java.lang.management.ManagementFactory;
import java.util.concurrent.TimeUnit;public class HelloAgent {public static void main(String[] args) throws MalformedObjectNameException, NotCompliantMBeanException, InstanceAlreadyExistsException, MBeanRegistrationException {MBeanServer server = ManagementFactory.getPlatformMBeanServer();ObjectName helloName = new ObjectName("MyMBean:name=helloDynamic");HelloDynamic hello = new HelloDynamic();server.registerMBean(hello,helloName);ObjectName adapterName = new ObjectName("MyMBean:name=htmladapter");HtmlAdaptorServer adapter = new HtmlAdaptorServer();server.registerMBean(adapter,adapterName);adapter.start();}
}

运行效果图如下：

运行结果：

Hello, null,this is HelloDynamic!
这是动态增加的一个方法print1

wanna more?

从零开始玩转JMX(一)——简介和Standard MBean
从零开始玩转JMX(二)——Condition
从零开始玩转JMX(三)——Model MBean
从零开始玩转JMX(四)——Apache Commons Modeler & Dynamic MBean

参考资料

JMX整理
JMX简介
http://blog.csdn.net/DryKillLogic/article/category/762777
用Apache的commons-modeler来辅助开发JMX

欢迎跳转到本文的原文链接：https://honeypps.com/java/jmx-quick-start-4-dynamic-mbean/

欢迎支持笔者新作：《深入理解Kafka:核心设计与实践原理》和《RabbitMQ实战指南》，同时欢迎关注笔者的微信公众号：朱小厮的博客。