学步园

先看Abstract...Pool的create(Object instance)函数热热身~
Abstract...Pool
// Protected -----------------------------------------------------
protected abstract EnterpriseContext create(Object instance)
throws Exception;
对Entity...Pool
protected EnterpriseContext create(Object instance)
throws Exception
{
return new EntityEnterpriseContext(instance, getContainer());
}
其他3种Pool类似。
再回头看Abstract..Pool
/** The pool data structure */
protected EnterpriseContext[] pool;
protected int currentIndex = -1;
/** The maximum number of instances allowed in the pool */
protected int maxSize = 30;
/** The minimum size of the pool */
protected int minSize = 0;
/** determine if we reuse EnterpriseContext objects i.e. if we actually do pooling */
protected boolean reclaim = false;//对于MDB和StatelessSessionBean,这个变量被设为true,// for MDB, we *do* pool // for SLSB, we *do* pool

ok,现在来看pool的重头戏，get()/free(EnterpriseContext ctx)函数
（discard(EnterpriseContext ctx)前面讲过，不再重复)
这几个函数也是Interface InstancePool里头要实现的接口：）
闲话少说，来看代码~~
protected boolean minSizeInitialized = false;

/**
* Get an instance without identity.
* Can be used by finders,create-methods, and activation
*
* @return Context /w instance
* @exception RemoteException
*/

public EnterpriseContext get() {
//pool里头有东东就拿出来
synchronized (pool)
{
if (currentIndex > -1)
{
EnterpriseContext ctx = pool[currentIndex];
pool[currentIndex--] = null;
return ctx;
}
}

//initialize a small fixed size of instance at startup.
if (!minSizeInitialized)
{
minSizeInitialized = true;
synchronized (pool)
{
for (int i = 0; i < minSize; i++)
{
pool[++currentIndex] = create(container.createBeanClassInstance());
}
}
}

// Pool is empty, create an instance
return create(container.createBeanClassInstance());
}

-----------------------------------------------------
而Stateful....Pool的free方法overwrite了Abstract...Pool的，
public synchronized void free(EnterpriseContext ctx)
{
discard(ctx);//干脆就discard掉不用了~
}

剩下的下回再讲，先预告2个类体系：
1.AbstractInstanceCache ,有EntityInstanceCache和StatefulSessionInstanceCache 子类。对于Entity,用它的
PrimaryKey作Cache的Key,对于Stateful,Jboss也会付给
每个instance一个唯一标定的值用来做CacheKey.
Abstract...Cache与Abstract...Pool结合使用，得到好的Performance。
2.public abstract class Container,
有EntityContainer,MessageDrivenContainer,Stateful/StatelessSessionContainer
4个子类，用来提供对EJB instance的transaction/security/pool等服务。
//看看它的成员变量，就能猜个大概
/** This is the TransactionManager */
protected TransactionManager tm;

/** This is the SecurityManager */
protected AuthenticationManager sm;

/** This is the EnterpriseBean class */
protected Class beanClass;

/** This is the Home interface class */
protected Class homeInterface;

/** This is the Remote interface class */
protected Class remoteInterface;

/** The local home interface class */
protected Class localHomeInterface;

/** The local inteface class */
protected Class localInterface;

/** This is the TransactionManager */
protected TransactionManager tm;

/** This is the SecurityManager */
protected AuthenticationManager sm;

/** This is the realm mapping */
protected RealmMapping rm;

/** This is the bean lock manager that is to be used */
protected BeanLockManager lockManager;

/** This is the application that this container is a part of */
protected EjbModule ejbModule;
//ejbModule作为一个单元部署的Module,比如一个ejb-jar就是一个Module,
/*这个 ejb-jar里头可能有多个entitybean,sessionbean,那么对于 每个entitybean,sessionbean
都会有一个对应的container,而这些东东共享一个ejbModule.*/
/**
* Returns a new instance of the bean class or a subclass of the bean class.
* This factory style method is speciffically used by a container to supply
* an implementation of the abstract accessors in EJB2.0, but could be
* usefull in other situations. This method should ALWAYS be used instead
* of getBeanClass().newInstance();
*
* @return the new instance
*
* @see java.lang.Class#newInstance
*/
public Object createBeanClassInstance() throws Exception {
return getBeanClass().newInstance();
}
public Class getBeanClass()
{
return beanClass;
}

注意EntityContainer overwrite了这个方法：
/**
* Returns a new instance of the bean class or a subclass of the bean class.
* If this is 1.x cmp, simply return a new instance of the bean class.
* If this is 2.x cmp, return a subclass that provides an implementation
* of the abstract accessors.
*
* @see java.lang.Class#newInstance
*
* @return The new instance.
*/
public Object createBeanClassInstance() throws Exception {
return persistenceManager.createBeanClassInstance();
}
其中 persistenceManager声明为：
/** This is the persistence manager for this container */
protected EntityPersistenceManager persistenceManager;
//persitenceManager和PersistenceStore我们将在第3部分讲解。
现在先给个大略印象：
BMPPersistenceManager实现
public Object createBeanClassInstance() throws Exception {
return con.getBeanClass().newInstance();
}

CMPPersistenceManager实现
EntityPersistenceStore store;
public Object createBeanClassInstance() throws Exception
{
return store.createBeanClassInstance();
}
-------------------------------------------------------------------
ok,接下来看看Container如何处理Client过来的Invocation。
一切精彩尽在下面这个函数
public Object invoke(Invocation mi)；
//Invocation代表了Client端过来的调用
//Invocation里头有些成员变量，指明了要调用的Method,
//args,Transaction信息，principle/credential等信息。

/** Maps for MarshalledInvocation mapping */
protected Map marshalledInvocationMapping = new HashMap();

public Object invoke(Invocation mi)
throws Exception
{
Thread currentThread = Thread.currentThread();
ClassLoader callerClassLoader = currentThread.getContextClassLoader();
//保存原来的classloader,在finally里恢复

Method m = null;
Object type = null;

try
{
currentThread.setContextClassLoader(this.classLoader);(注3）
// Check against home, remote, localHome, local, getHome,
// getRemote, getLocalHome, getLocal
type = mi.getType();

if(type == InvocationType.REMOTE ||
type == InvocationType.LOCAL)
{
if (mi instanceof MarshalledInvocation)
{
((MarshalledInvocation) mi).setMethodMap(
marshalledInvocationMapping);
}
return internalInvoke(mi);
}
else if(type == InvocationType.HOME ||
type == InvocationType.LOCALHOME)
{
if (mi instanceof MarshalledInvocation)
{
((MarshalledInvocation) mi).setMethodMap(
marshalledInvocationMapping);
return internalInvokeHome(mi);
}
else
{
throw new MBeanException(new IllegalArgumentException(
///////"Unknown invocation type: ///////" + type));
}
}
finally
{
currentThread.setContextClassLoader(callerClassLoader);
}
}

----------------------------------------------------------------
MarshalledInvocation是Invocation的字类，代表可以从
Client传到Server的Invocation
public class Invocation...

public class MarshalledInvocation
extends Invocation
implements java.io.Externalizable
而Invocation是在server端的调用链(Interceptor链，注4）
间传递.
-------------------------------------------------------
ok,稍喘口气，接下来看看两个Internal的invoke,
都是abstract,在字类实现
public abstract Object internalInvokeHome(Invocation mi)
throws Exception;
public abstract Object internalInvoke(Invocation mi)
throws Exception;
至于具体实现么，TO BE CONITUE拉:)
----------------------------------------------------
注1：ContainerPlugin可以放在容器里头的东东。
接口为interface ContainerPlugin ：
void setContainer(Container con);
有InstancePool,InstanceCache,EJBProxyFactory/LocalProxyFactory,
EntityPersistenceManager/EntityPersistenceStore等Plugin
注2：metadata描述部署的信息，比如ejb-jar.xml，描述什么东东是
entitybean,什么东东是sessionbean,session的是BMP/CMP等等。
注3： Container的成员变量protected ClassLoader classLoader;
用来load 这个Container里头的类和资源，之所以要专门设一个Container
的classLoader是因为能使EJB re-deployable.(JBoss定期扫描deploy目录，
如果ejb更改就进行redeploy,如果ejb删除就undeploy)
注4： Jboss会建立一个Interceptor 链，Invocation经过链传递。
比如有EntityInterceptor，SecurityInterceptor，TransactionInterceptor，
InvokerInterceptor，一个套一个，每个Interceptor对当前Invocation进行一些处理
，比如检查权限，事物等等，然后传给下一个Interceptor处理(这是Filter and Pipe模式了，也算是AOP拉~，别人说
JBoss 这个Interceptor实现属于AOP方言特别重：）。
所有的Interceptor都是现
Object invokeHome(Invocation mi) throws Exception;
和Object invoke(Invocation mi) throws Exception;
在自己invoke的最后，
经过所有的Interceptor之后，调用下一个。
看看AbstractInterceptor的缺省实现：
public abstract class AbstractInterceptor
implements Interceptor

public Object internalInvoke(Invocation mi) throws Exception
{
// Invoke through interceptors
return getInterceptor().invoke(mi);
}

public Interceptor getInterceptor()
{
return interceptor;
}
protected Interceptor interceptor;
//这是Container建立的Interceptor链的头一个，从这里调起~
再来看看 void addInterceptor(Interceptor in);这个函数
在Interceptor链最后再挂一个Interceptor
public void addInterceptor(Interceptor in)
{
if (interceptor == null)
{
interceptor = in;
}
else
{
Interceptor current = interceptor;
while (current.getNext() != null)
{
current = current.getNext();
}

current.setNext(in);
}
}
------------------------------------------------------------------------
附带再提一下pool和cache
/** This is the instance cache for this container */
protected InstanceCache instanceCache;

/** This is the instancepool that is to be used */
protected InstancePool instancePool;
/** This is the instancepool that is to be used */
protected InstancePool instancePool;
-------------------------------------------------------------
public void setInstanceCache(InstanceCache ic)
{
if (ic == null)
throw new IllegalArgumentException(///"Null cache///");

this.instanceCache = ic;
ic.setContainer(this);
}

public InstanceCache getInstanceCache()
{
return instanceCache;
}
public void setInstancePool(InstancePool ip)
{
if (ip == null)
throw new IllegalArgumentException(///"Null pool///");

this.instancePool = ip;
ip.setContainer(this);
}
-----------------------------------------------------------------------
ok,现在让我们来看看Container都对EJB Instance暴露出来的
方法都作了些什么，还有如何调用EJB Instance的方法.
这里有重要的2个Map
/**
* These are the mappings between the home interface methods and the
* container methods.
* 所有Home 方法映射都存这里
*/
protected Map homeMapping = new HashMap();

/**
* These are the mappings between the remote/local interface methods and the
* bean methods.
* 所有EJBObject方法映射都存这里
*/
protected Map beanMapping = new HashMap();
--------------------------------------------------------------------------
class ContainerInterceptor
extends AbstractContainerInterceptor
//AbstractContainerInterceptor基本上什么都不做，不用看
//ContainerInterceptor代表Container setup的Interceptor调用
//链的最后一个，到这里你就会看到他调用了你的EJB Instance的方法
{
public Object invokeHome(Invocation mi) throws Exception
{
// Invoke and handle exceptions
Method miMethod = mi.getMethod();
Method m = (Method) homeMapping.get(miMethod);
if (m.getDeclaringClass().equals(EntityContainer.class))
{
try
{
return m.invoke(EntityContainer.this, new Object[] { mi });
}
catch (Exception e)
{
rethrow(e);
}
}
else // Home method
{
try
{
return m.invoke(((EnterpriseContext) mi.getEnterpriseContext()).getInstance(), mi.getArguments());
}
catch (Exception e)
{
rethrow(e);
}
}

// We will never get this far, but the compiler does not know that
throw new org.jboss.util.UnreachableStatementException();
}

public Object invoke(Invocation mi) throws Exception
{
// Get method
Method miMethod = mi.getMethod();
Method m = (Method) beanMapping.get(miMethod);
if( m == null )
{
String msg = ///"Invalid invocation, check your deployment packaging///"
+///", method=///"+miMethod;
throw new EJBException(msg);
}

// Select instance to invoke (container or bean)
if (m.getDeclaringClass().equals(EntityContainer.class))
{
// Invoke and handle exceptions
try
{
return m.invoke(EntityContainer.this, new Object[]{ mi });
}
catch (Exception e)
{
rethrow(e);
}
}
else
{
// Invoke and handle exceptions
try
{
return m.invoke(((EnterpriseContext) mi.getEnterpriseContext()).getInstance(), mi.getArguments());
}
catch (Exception e)
{
rethrow(e);
}
}

// We will never get this far, but the compiler does not know that
throw new org.jboss.util.UnreachableStatementException();
}
}

protected void createService() throws Exception
{
// Associate thread with classloader
ClassLoader oldCl = Thread.currentThread().getContextClassLoader();
Thread.currentThread().setContextClassLoader(getClassLoader());

try
{
// Acquire classes from CL
//从metadata拿到Home/Remote的Class
if (metaData.getHome() != null)
homeInterface = classLoader.loadClass(metaData.getHome());
if (metaData.getRemote() != null)
remoteInterface = classLoader.loadClass(metaData.getRemote());

// Call default init
// 调用Container里头的CreateService,我们回头再看
super.createService();

//建立刚才所说的两个Method映射Map
setupBeanMapping();
setupHomeMapping();

// Map the interfaces to Long
setupMarshalledInvocationMapping();

// Initialize pool
instancePool.create();
// Try to register the instance pool as an MBean
try
{
ObjectName containerName = super.getJmxName();
Hashtable props = containerName.getKeyPropertyList();
props.put(///"plugin///", ///"pool///");
ObjectName poolName = new ObjectName(containerName.getDomain(), props);
server.registerMBean(instancePool, poolName);
}
catch(Throwable t)
{
log.debug(///"Failed to register cache as mbean///", t);
}

// Init instance cache
instanceCache.create();
// Try to register the instance cache as an MBean
try
{
ObjectName containerName = super.getJmxName();
Hashtable props = containerName.getKeyPropertyList();
props.put(///"plugin///", ///"cache///");
ObjectName cacheName = new ObjectName(containerName.getDomain(), props);
server.registerMBean(instanceCache, cacheName);
}
catch(Throwable t)
{
log.debug(///"Failed to register cache as mbean///", t);
}

for (Iterator it = proxyFactories.keySet().iterator(); it.hasNext(); )
{
String invokerBinding = (String)it.next();
EJBProxyFactory ci = (EJBProxyFactory)proxyFactories.get(invokerBinding);
ci.create();
}

// Init persistence
persistenceManager.create();

// Initialize the interceptor by calling the chain
Interceptor in = interceptor;
while (in != null)
{
in.setContainer(this);
in.create();
in = in.getNext();
}
readOnly = ((EntityMetaData)metaData).isReadOnly();
}
finally
{
// Reset classloader
Thread.currentThread().setContextClassLoader(oldCl);
}
}

protected void startService() throws Exception
{
// Associate thread with classloader
ClassLoader oldCl = Thread.currentThread().getContextClassLoader();
Thread.currentThread().setContextClassLoader(getClassLoader());

try
{
// Call default start
super.startService();

// Start container invokers
for (Iterator it = proxyFactories.keySet().iterator(); it.hasNext(); )
{
String invokerBinding = (String)it.next();
EJBProxyFactory ci = (EJBProxyFactory)proxyFactories.get(invokerBinding);
ci.start();
}

// Start instance cache
instanceCache.start();

// Start persistence
persistenceManager.start();

// Start the instance pool
instancePool.start();

// Start all interceptors in the chain
Interceptor in = interceptor;
while (in != null)
{
in.start();
in = in.getNext();
}
}
finally
{
// Reset classloader
Thread.currentThread().setContextClassLoader(oldCl);
}
}

protected void stopService() throws Exception
{
// Associate thread with classloader
ClassLoader oldCl = Thread.currentThread().getContextClassLoader();
Thread.currentThread().setContextClassLoader(getClassLoader());

try
{
//Stop items in reverse order from start
//This assures that CachedConnectionInterceptor will get removed
//from in between this and the pm before the pm is stopped.
// Stop all interceptors in the chain
Interceptor in = interceptor;
while (in != null)
{
in.stop();
in = in.getNext();
}

// Stop the instance pool
instancePool.stop();

// Stop persistence
persistenceManager.stop();

// Stop instance cache
instanceCache.stop();

// Stop container invoker
for (Iterator it = proxyFactories.keySet().iterator(); it.hasNext(); )
{
String invokerBinding = (String)it.next();
EJBProxyFactory ci = (EJBProxyFactory)proxyFactories.get(invokerBinding);
ci.stop();
}

// Call default stop
super.stopService();
}
finally
{
// Reset classloader
Thread.currentThread().setContextClassLoader(oldCl);
}
}

protected void destroyService() throws Exception
{
// Associate thread with classloader
ClassLoader oldCl = Thread.currentThread().getContextClassLoader();
Thread.currentThread().setContextClassLoader(getClassLoader());

try
{
// Destroy container invoker
for (Iterator it = proxyFactories.keySet().iterator(); it.hasNext(); )
{
String invokerBinding = (String)it.next();
EJBProxyFactory ci = (EJBProxyFactory)proxyFactories.get(invokerBinding);
ci.destroy();
}

// Destroy instance cache
instanceCache.destroy();
instanceCache.setContainer(null);
try
{
ObjectName containerName = super.getJmxName();
Hashtable props = containerName.getKeyPropertyList();
props.put(///"plugin///", ///"cache///");
ObjectName cacheName = new ObjectName(containerName.getDomain(), props);
server.unregisterMBean(cacheName);
}
catch(Throwable ignore)
{
}

// Destroy persistence
persistenceManager.destroy();
persistenceManager.setContainer(null);

// Destroy the pool
instancePool.destroy();
instancePool.setContainer(null);
try
{
ObjectName containerName = super.getJmxName();
Hashtable props = containerName.getKeyPropertyList();
props.put(///"plugin///", ///"pool///");
ObjectName poolName = new ObjectName(containerName.getDomain(), props);
server.unregisterMBean(poolName);
}
catch(Throwable ignore)
{
}

// Destroy all the interceptors in the chain
Interceptor in = interceptor;
while (in != null)
{
in.destroy();
in.setContainer(null);
in = in.getNext();
}

MarshalledInvocation.removeHashes(homeInterface);
MarshalledInvocation.removeHashes(remoteInterface);

// Call default destroy
super.destroyService();
}
finally
{
// Reset classloader
Thread.currentThread().setContextClassLoader(oldCl);
}
}
------------------------------------------------------------
protected void setupBeanMapping() throws Exception
{
try {
if (remoteInterface != null)
{
Method[] m = remoteInterface.getMethods();
setupBeanMappingImpl( m, ///"javax.ejb.EJBObject///" );
}
if (localInterface != null)
{
Method[] m = localInterface.getMethods();
setupBeanMappingImpl( m, ///"javax.ejb.EJBLocalObject///" );
}
}
catch (Exception e)
{
// ditch the half built mappings
homeMapping.clear();
beanMapping.clear();

throw e;
}
}