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

本文链接：https://blog.youkuaiyun.com/iteye_1364/article/details/82032664

本文详细解析了Tomcat7服务器启动过程中JMX组件的初始化流程，重点关注了DynamicMBean的注册过程，并介绍了涉及的关键类如BaseModelMBean、ManagedBean及Registry的作用。

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

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

Java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[i].init();
}
}

    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[i].init();
        }
    }

先看super.initInternal();

Java代码

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());
}
}

    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。

Java代码

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;
}

    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

Java代码

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;
}
}

 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。