tomcat 7 源码分析-5 server初始化中的JMX(DynamicMBean)

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　　Server的中的初始化基本核心在StandardServer中，下面的代码

    protected void initInternal() throws LifecycleException {
super.initInternal();
// Register global String cache
// Note although the cache is global, if there are multiple Servers
// present in the JVM (may happen when embedding) then the same cache
// will be registered under multiple names
onameStringCache = register(new StringCache(), "type=StringCache");
// Register the MBeanFactory
onameMBeanFactory = register(new MBeanFactory(), "type=MBeanFactory");
// Register the naming resources
onameNamingResoucres = register(globalNamingResources,
"type=NamingResources");
// Initialize our defined Services
for (int i = 0; i < services.length; i++) {
services.init();
}
}
　　先看super.initInternal();

    protected void initInternal() throws LifecycleException {
// If oname is not null then registration has already happened via
// preRegister().
if (oname == null) {
mserver = Registry.getRegistry(null, null).getMBeanServer();
oname = register(this, getObjectNameKeyProperties());
}
}
　　看来问题的关键就在register这个函数了。

    protected final ObjectName register(Object obj,
String objectNameKeyProperties) {
// Construct an object name with the right domain
StringBuilder name = new StringBuilder(getDomain());
name.append(':');
name.append(objectNameKeyProperties);
ObjectName on = null;
try {
on = new ObjectName(name.toString());
Registry.getRegistry(null, null).registerComponent(obj, on, null);
} catch (MalformedObjectNameException e) {
log.warn(sm.getString("lifecycleMBeanBase.registerFail", obj, name),
e);
} catch (Exception e) {
log.warn(sm.getString("lifecycleMBeanBase.registerFail", obj, name),
e);
}
return on;
}
　　接下去看registerComponent函数

public void registerComponent(Object bean, ObjectName oname, String type)
throws Exception
{
if( log.isDebugEnabled() ) {
log.debug( "Managed= "+ oname);
}
if( bean ==null ) {
log.error("Null component " + oname );
return;
}
try {
if( type==null ) {
type=bean.getClass().getName();
}
ManagedBean managed = findManagedBean(bean.getClass(), type);
// The real mbean is created and registered
DynamicMBean mbean = managed.createMBean(bean);
if(  getMBeanServer().isRegistered( oname )) {
if( log.isDebugEnabled()) {
log.debug("Unregistering existing component " + oname );
}
getMBeanServer().unregisterMBean( oname );
}
getMBeanServer().registerMBean( mbean, oname);
} catch( Exception ex) {
log.error("Error registering " + oname, ex );
throw ex;
}
}
　　终于知道这一段代码要完成什么功能了，原来register就是将参数中的object注册到MBeanServer中去，而且使用的是DynamicMBean。
　　Tomcat中
　　BaseModelMBean实现了DynamicMBean接口，是真正意思上的动态Mbeans。
　　ManagedBean是对MBeans的管理，例如生产Mbean等。
　　Registry是又一层次的封装，是将Object(Mbeans)注册到MBeanServer的一个接口，同时还提供对已有Mbeans的查找，防止重复注册等。
　　说到这里，如果不了解MBean的话，肯定不知道在说什么。所以我下一个续，先从简单的Standard MBeans说起。