一、JMX简介
官网学习地址：http://docs.oracle.com/javase/tutorial/jmx/index.html
The Java Management Extensions (JMX) technology is a standard part of the Java Platform, Standard Edition (Java SE platform). The JMX technology was added to the platform in the Java 2 Platform, Standard Edition (J2SE) 5.0 release.
The JMX technology provides a simple, standard way of managing resources such as applications, devices, and services. Because the JMX technology is dynamic, you can use it to monitor and manage resources as they are created, installed and implemented. You can also use the JMX technology to monitor and manage the Java Virtual Machine (Java VM).
The JMX specification defines the architecture, design patterns, APIs, and services in the Java programming language for management and monitoring of applications and networks.
Using the JMX technology, a given resource is instrumented by one or more Java objects known as Managed Beans, or MBeans. These MBeans are registered in a core-managed object server, known as an MBean server. The MBean server acts as a management agent and can run on most devices that have been enabled for the Java programming language.
The specifications define JMX agents that you use to manage any resources that have been correctly configured for management. A JMX agent consists of an MBean server, in which MBeans are registered, and a set of services for handling the MBeans. In this way, JMX agents directly control resources and make them available to remote management applications.
The way in which resources are instrumented is completely independent from the management infrastructure. Resources can therefore be rendered manageable regardless of how their management applications are implemented.
The JMX technology defines standard connectors (known as JMX connectors) that enable you to access JMX agents from remote management applications. JMX connectors using different protocols provide the same management interface. Consequently, a management application can manage resources transparently, regardless of the communication protocol used. JMX agents can also be used by systems or applications that are not compliant with the JMX specification, as long as those systems or applications support JMX agents.
JMX的主要目的是让程序有被管理的能力，假设你拥有一个电商网站，那么你可能想监控网站的运行情况，比如在线客户、交易金额、数据库连接池等信息，如果当前在线人数非常大，而服务器还有更大的负荷空间，那么我们通常的做法是修改配置文件，然后重启服务，此时必然会影响用户的交易从而造成非常大的损失。JMX的引入为我们解决了这个难题，不用重启服务却能是配置的更改生效。
