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如何自己监控java

使用JMX

JAVA Management Extensions的缩写,Java自带的一种管理资源的技术,比如对Java 应用程序,系统和网络等

java自带的获取各种信息的工具类

java自带的java.lang.management.ManagementFactory 可以看到它提供的一些列方法:

可以看到它提供了包括类加载、内存、线程等MXBean

以Memory为例,它包括两部分,MemoryMXBean和MemoryPoolMXBean

/**
 * Returns the managed bean for the memory system of
 * the Java virtual machine.
 *
 * @return a {@link MemoryMXBean} object for the Java virtual machine.
 */
public static MemoryMXBean getMemoryMXBean() {
    return ManagementFactoryHelper.getMemoryMXBean();
}
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MemoryMXBean提供获取堆内存和非堆内存的方法,返回对象MemoryUsage相应包含最大、已使用等信息

/**
 * Returns the current memory usage of the heap that
 * is used for object allocation.  The heap consists
 * of one or more memory pools.  The <tt>used</tt>
 * and <tt>committed</tt> size of the returned memory
 * usage is the sum of those values of all heap memory pools
 * whereas the <tt>init</tt> and <tt>max</tt> size of the
 * returned memory usage represents the setting of the heap
 * memory which may not be the sum of those of all heap
 * memory pools.
 * <p>
 * The amount of used memory in the returned memory usage
 * is the amount of memory occupied by both live objects
 * and garbage objects that have not been collected, if any.
 *
 * <p>
 * <b>MBeanServer access</b>:<br>
 * The mapped type of <tt>MemoryUsage</tt> is
 * <tt>CompositeData</tt> with attributes as specified in
 * {@link MemoryUsage#from MemoryUsage}.
 *
 * @return a {@link MemoryUsage} object representing
 * the heap memory usage.
 */
public MemoryUsage getHeapMemoryUsage();
/**
 * Returns the current memory usage of non-heap memory that
 * is used by the Java virtual machine.
 * The non-heap memory consists of one or more memory pools.
 * The <tt>used</tt> and <tt>committed</tt> size of the
 * returned memory usage is the sum of those values of
 * all non-heap memory pools whereas the <tt>init</tt>
 * and <tt>max</tt> size of the returned memory usage
 * represents the setting of the non-heap
 * memory which may not be the sum of those of all non-heap
 * memory pools.
 *
 * <p>
 * <b>MBeanServer access</b>:<br>
 * The mapped type of <tt>MemoryUsage</tt> is
 * <tt>CompositeData</tt> with attributes as specified in
 * {@link MemoryUsage#from MemoryUsage}.
 *
 * @return a {@link MemoryUsage} object representing
 * the non-heap memory usage.
 */
public MemoryUsage getNonHeapMemoryUsage();
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MemoryPoolMXBean能够获取 memory pool的名字,比如是否是Eden区,old区等等

/**
 * Returns a list of {@link MemoryPoolMXBean} objects in the
 * Java virtual machine.
 * The Java virtual machine can have one or more memory pools.
 * It may add or remove memory pools during execution.
 *
 * @return a list of <tt>MemoryPoolMXBean</tt> objects.
 *
 */
public static List<MemoryPoolMXBean> getMemoryPoolMXBeans() {
    return ManagementFactoryHelper.getMemoryPoolMXBeans();
}
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要获取整个的内存大小,需要使用Runtime

/**
 * Returns the amount of free memory in the Java Virtual Machine.
 * Calling the
 * <code>gc</code> method may result in increasing the value returned
 * by <code>freeMemory.</code>
 *
 * @return  an approximation to the total amount of memory currently
 *          available for future allocated objects, measured in bytes.
 */
public native long freeMemory();

/**
 * Returns the total amount of memory in the Java virtual machine.
 * The value returned by this method may vary over time, depending on
 * the host environment.
 * <p>
 * Note that the amount of memory required to hold an object of any
 * given type may be implementation-dependent.
 *
 * @return  the total amount of memory currently available for current
 *          and future objects, measured in bytes.
 */
public native long totalMemory();

/**
 * Returns the maximum amount of memory that the Java virtual machine will
 * attempt to use.  If there is no inherent limit then the value {@link
 * java.lang.Long#MAX_VALUE} will be returned. </p>
 *
 * @return  the maximum amount of memory that the virtual machine will
 *          attempt to use, measured in bytes
 * @since 1.4
 */
public native long maxMemory();
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获取其它想要监控的信息

通过java.lang.management.ManagementFactory 获取 MBeanServer,平台所有的MBean都会注册到这个上面。然后通过获取ObjectName和属性就能获得值

JMX的架构

分成3块:Instrumentation,JMX agent和Remote management

  • Instrumentation: 使用MBeans来实现资源检测(resources' instrumentation),MBeans有一套标准的规范,实现MBeans必须遵循,以实现标准化的处理

  • JMX Agent: 用于直接的控制资源,并使得远程管理应用能够获取这些资源,它通常和控制的资源在同一台机器上。JMX Agent的核心组件是MBean server[]MBeans注册的地方]

  • Remote management: JMX Agent实现的不同协议适配器和connector使得注册在MBean server上的MBeans都能够被看到,比如HTML的adaptor能够使得浏览器上能够展示MBean

MBean

一个MBean可以代表一个设备,应用或者任何可以被管理的资源。MBeans会暴漏具有如下特性的管理接口:

  • 可读可写的属性集合:读对应着 get开头的方法,必须有返回值;写对应着set开头的方法

  • 可调用操作的集合:自定义的一下方法

  • 一段自我的描述

标准的MBeans

包含两个部分:MBean的接口和它的实现类。命名接口为 xxxMBean 。比如命名为 PaxiMBean,然后用一个java类 Paxi来实现这个接口。

MBean

package main.jmx;
public interface PaxiMBean {
    void sayHi();
    String getName();
    void setName(String name);
}
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Mbean实现

public class Paxi implements PaxiMBean {
    @Override
    public void sayHi() {
        System.out.println("hi");
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public void setName(String name) {
        this.name=name;
    }
    private String name="paxi";
}
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Agent例子

package main.jmx;
public class MyAgent {
    public static void main(String[] args) {
        //1:获取平台已经创建并初始化的MBeanServer,没有就通过MBeanServerFactory.createMBeanServer()创建
        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        try {
            //2:每个MBean必须有一个object name,name遵照标准格式
            ObjectName name = new ObjectName("main.jmx:type=Paxi");
            Paxi paxi = new Paxi();
            //3:注册MBean
            mbs.registerMBean(paxi,name);
            System.out.println("wait for incoming request");
            Thread.sleep(Long.MAX_VALUE);
        } catch (MalformedObjectNameException e) {
            e.printStackTrace();
        } catch (NotCompliantMBeanException e) {
            e.printStackTrace();
        } catch (InstanceAlreadyExistsException e) {
            e.printStackTrace();
        } catch (MBeanRegistrationException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
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在命令行运行 jconsole,选中MBean,点击左侧栏 main.jmx

得到操作界面
点击sayHi,会弹窗提示调用成功

此时界面上会出现 sayHi的内容

wait for incoming request
hi
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MXBeans

它是一种MBean的一种,仅用来引用一种预定义的数据类型。它的定义为 方式可以和MBean一样。接口后缀为MXBean然后在实现

public interface PaxiQMXBean {
    PaxiQueue getPaxiQueue();
    void clearQueue();
}
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或者是使用MXBean的注解

@MXBean
public interface PaxiQInAnnotation {
    PaxiQueue getPaxiQueue();
    void clearQueue();
}
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实现

public class PaxiQ implements PaxiQMXBean {
    private Queue<String> queue;

    public PaxiQ(Queue<String> queue) {
        this.queue = queue;
    }

    @Override
    public PaxiQueue getPaxiQueue() {
        synchronized (queue){
            return new PaxiQueue(new Date(),queue.size(),queue.peek());
        }
    }

    @Override
    public void clearQueue() {
        synchronized (queue){
            queue.clear();
        }
    }
}
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其中的PaxiQueue是自己定义的一个对象

public class PaxiQueue {
    private final Date date;
    private final int size;
    private final String head;

    @ConstructorProperties({"date","size","head"})
    public PaxiQueue(Date date, int size, String head) {
        this.date = date;
        this.size = size;
        this.head = head;
    }

    public Date getDate() {
        return date;
    }

    public String getHead() {
        return head;
    }

    public int getSize() {
        return size;
    }
}
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Agent的实现为

public class MyAgent {
    public static void main(String[] args) {
        //1:获取平台已经创建并初始化的MBeanServer,没有就通过MBeanServerFactory.createMBeanServer()创建
        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        try {
            ObjectName name = new ObjectName("main.jmx:type=PaxiQ");
            Queue<String> queue = new ArrayBlockingQueue<String>(10);
            queue.add("r-1");
            queue.add("r-2");
            queue.add("r-3");
            PaxiQ mxbean = new PaxiQ(queue);
            //3:注册MBean
            mbs.registerMBean(mxbean,name);
            System.out.println("wait for incoming request");
            Thread.sleep(Long.MAX_VALUE);
        } catch (MalformedObjectNameException e) {
            e.printStackTrace();
        } catch (NotCompliantMBeanException e) {
            e.printStackTrace();
        } catch (InstanceAlreadyExistsException e) {
            e.printStackTrace();
        } catch (MBeanRegistrationException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
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启动后运行jconsole

可以看到自定义的属性值为CompositeDataSupport,双击它可以看到等他的内容:

但是如果PaxiQMXBean是一个MBean,即名字是PaxiQMBean,这个时候通过jconsole是无法找到的。

创建一个自己的JMX client

JMX client代码

public class PaxiClient {
    public static void main(String[] args) {
        System.out.println("create RMI client");
        try {
            JMXServiceURL url = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://:9999/jmxrmi");
            JMXConnector jmxConnector = JMXConnectorFactory.connect(url, null);
            MBeanServerConnection mBeanServerConnection = jmxConnector.getMBeanServerConnection();
            System.out.println("domains");
            String[] domains= mBeanServerConnection.getDomains();
            Arrays.sort(domains);
            for (String domain:domains){
                System.out.println(domain);
            }
            System.out.println("domain:"+mBeanServerConnection.getDefaultDomain());
            System.out.println("MBean count:"+mBeanServerConnection.getMBeanCount());
            Set<ObjectName> names = new TreeSet<ObjectName>(mBeanServerConnection.queryNames(null,null));
            for (ObjectName name:names){
                System.out.println("objectname:"+name);
            }
            ObjectName mbeanName = new ObjectName("main.jmx:type=Paxi");
            PaxiMBean mbeanProxy = JMX.newMBeanProxy(mBeanServerConnection,mbeanName,PaxiMBean.class,true);
            System.out.println("add notification listener..");
          // 自定义消息的监听
            PaxiClientListener listener = new PaxiClientListener();
            mBeanServerConnection.addNotificationListener(mbeanName,listener,null,null);
            mbeanProxy.setName("new name");
            System.out.println("wait notifacaion");
            TimeUnit.SECONDS.sleep(2);
            System.out.println(mbeanProxy.getName());
            mbeanProxy.sayHi();
            TimeUnit.SECONDS.sleep(10);
            jmxConnector.close();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (MalformedObjectNameException e) {
            e.printStackTrace();
        } catch (InstanceNotFoundException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
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listener

public class PaxiClientListener implements NotificationListener{
    @Override
    public void handleNotification(Notification notification, Object handback) {
        System.out.println("r notification");
        System.out.println("class:"+notification.getClass().getName());
        System.out.println("Source:"+notification.getSource());
        System.out.println("Type:"+notification.getType());
        System.out.println("Message:"+notification.getMessage());
        if (notification instanceof AttributeChangeNotification){
            AttributeChangeNotification n= (AttributeChangeNotification) notification;
            System.out.println("attr name:"+n.getAttributeName());
            System.out.println("attr type:"+n.getAttributeType());
            System.out.println("attr new Value:"+n.getNewValue());
            System.out.println("attr old Value:"+n.getOldValue());
        }
    }
}
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jmx 官方文档