tomcat 7 源码分析-6 server初始化中的JMX(DynamicMBean)续-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_1364/article/details/82032665

本文介绍如何使用JMX技术在不重启应用的情况下动态调整连接数。通过定义MBean接口、实现该接口并注册到MBeanServer中，实现对应用参数的动态管理。

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tomcat 7 源码分析-6 server初始化中的JMX(DynamicMBean)续

先说JMX，The JMX technology provides a simple, standard way of managing resources such as applications, devices, and services.

JMX是为了管理资源产生的，这个资源包括应用、设备和服务等。取个例子，如果你写了一个应用，初始化了20个的数据连接数，当你的应用还在跑的时候，发觉这个连接数少了，你要增加这个参数。JMX提供不需要停机，动态的管理连接数的方法。

先从简单的Standard MBeans看起。

通常我们先定义interface

第一步：MBean Interface

Java代码

package com.example;
public interface ConnectionNumberMBean {
public int getConnectionNumber();
public void setConnectionNumber( int num);
}

package com.example; 
 
public interface ConnectionNumberMBean { 
    public int getConnectionNumber(); 
    public void setConnectionNumber(int num); 
}

第二步：实现接口

Java代码

package com.example;
import javax.management.*;
public class ConnectionNumber extends NotificationBroadcasterSupport implements ConnectionNumberMBean {
public int getConnectionNumber() {
return this .conNum ;
}
public synchronized void setConnectionNumber( int con_Num ) {
this .conNum = con_Num ;
System.out.println("Connection number now " + this .conNum );
}
private int conNum = DEFAULT_CON_Num;
private static final int DEFAULT_CON_Num= 20 ;
}

package com.example; 
import javax.management.*;
public class ConnectionNumber extends NotificationBroadcasterSupport implements ConnectionNumberMBean { 
 
    public int getConnectionNumber() { 
	return this.conNum ; 
    } 
 
    public synchronized void setConnectionNumber(int con_Num ) {

	this.conNum = con_Num ; 
 
	System.out.println("Connection number now " + this.conNum ); 
    } 
    private int conNum = DEFAULT_CON_Num;
    private static final int DEFAULT_CON_Num= 20; 
}

第三步：创建a JMX Ageng来管理资源

Java代码

package com.example;
import java.lang.management.ManagementFactory;
import javax.management.MBeanServer;
import javax.management.ObjectName;
public class Main {
/* For simplicity, we declare "throws Exception".
Real programs will usually want finer-grained exception handling. */
public static void main(String[] args) throws Exception {
// Get the Platform MBean Server
MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
// Construct the ObjectName for the Hello MBean we will register
ObjectName mbeanName = new ObjectName( "com.example:type=ConnectionNumber" );
// Create the Hello World MBean
ConnectionNumber mbean = new ConnectionNumber();
// Register the Hello World MBean
mbs.registerMBean(mbean, mbeanName);
// Wait forever
System.out.println("Waiting for incoming requests..." );
Thread.sleep(Long.MAX_VALUE);
}
}

package com.example;

import java.lang.management.ManagementFactory;
import javax.management.MBeanServer;
import javax.management.ObjectName;

public class Main {
    /* For simplicity, we declare "throws Exception".
       Real programs will usually want finer-grained exception handling. */
    public static void main(String[] args) throws Exception {
        // Get the Platform MBean Server
        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();

	// Construct the ObjectName for the Hello MBean we will register
	ObjectName mbeanName = new ObjectName("com.example:type=ConnectionNumber");

	// Create the Hello World MBean
	ConnectionNumber  mbean = new ConnectionNumber();

	// Register the Hello World MBean
	mbs.registerMBean(mbean, mbeanName);

        // Wait forever
        System.out.println("Waiting for incoming requests...");
        Thread.sleep(Long.MAX_VALUE);
    }
}

编译生产Class文件后，运行它。

打开windows控制台，运行jconsole命令，打开java控制台，如下图。