每個(gè)bean可能會(huì)有很多方法，一般我們通過一個(gè)delegate來調(diào)用sessionbean中的方法，而非直接調(diào)用sessionbean,delegate中只是簡單的對(duì)每個(gè)相對(duì)應(yīng)的sessionbean的public方法的簡單封裝，在調(diào)用的時(shí)候省去了每次對(duì)home的查找和ejb對(duì)象的create,但是可能我們的bean會(huì)有很多方法，假如每個(gè)bean都寫這樣一個(gè)delegate,這樣工作量就會(huì)很大，而且也不便于以后系統(tǒng)的移植，比如說，原來使用ejb實(shí)現(xiàn)，現(xiàn)在要改用jdo直接操作數(shù)據(jù)庫，而通過運(yùn)用java的reflect技術(shù)，就能較好地實(shí)現(xiàn)這些要求。首先，定義了一個(gè)FacadeDelegate的抽象類，用來實(shí)現(xiàn)對(duì)sessionbean的home的查找,代碼如下：

import javax.ejb.*;

import testejb.util.common.*;

import testejb.util.resource.*;

public abstract class FacadeDelegate{PRivate static String type = Resource.RemoteType;

public FacadeDelegate() {

}

public EJBHome getHome(String jindiName,Class className)

{

EJBHome home = null;

ServerLocatorAdapter adapter = ServerLocatorAdapter.getInstance();

try

{

home = (EJBHome)adapter.getHome(type, jindiName, className);

}

catch(Exception e)

{

System.err.println(e.getMessage() + jindiName + className.toString());

}

return home;

}}

其中ServerLocatorAdapter是一個(gè)用來根據(jù)是local還是remote調(diào)用ejb對(duì)象而通過不同的方法查找home的類，假如type為local則調(diào)用LocalServerLocate中的方法，假如type為remote則調(diào)用RemoteServerLocate中的方法，獲得home。代碼如下:

import java.util.*;

import java.lang.reflect.*;

import testejb.util.resource.*;

public class ServerLocatorAdapter {private Map cache;//用來緩存home

private static ServerLocatorAdapter me;

public static ServerLocatorAdapter getInstance()

{if(me == null)

me = new ServerLocatorAdapter();

return me;

}

//取得home

public Object getHome(String type,String jndiHomeName,Class className) throws Exception

{Object home = null;

if(cache.containsKey(jndiHomeName))

return cache.get(jndiHomeName);

if(Resource.LocalType.equals(type))

{

home = getLocalHome(jndiHomeName,className);

cache.put(jndiHomeName,home);

return home;

}

if(Resource.RemoteType.equals(type))

{

home = getRemoteHome(jndiHomeName,className);

cache.put(jndiHomeName,home);

return home;

}

return home;}

//取得local home

private Object getLocalHome(String jndiHomeName,Class className) throws Exception

{

Class myClass = Class.forName(Resource.LocalClass);

// Resource. LocalClass =”testejb.util.common. LocalServerLocator

Method method = myClass.getMethod(Resource.LocalConstractMethod,null);

// Resource. LocalConstractMethod =” getInstance”

LocalServerLocator local = null;

local = (LocalServerLocator)method.invoke(myClass,null);

return local.getLocalHome(jndiHomeName,className);

}

//取得remote home

private Object getRemoteHome(String jndiHomeName,Class className) throws Exception

{

Class myClass = Class.forName(Resource.RemoteClass);

// Resource.RemoteClass =”testejb.util.common.RemoteServerLocator”

Method method = myClass.getMethod(Resource.RemoteConstractMethod,null);

// Resource.RemoteConstractMethod=” getInstance”

RemoteServerLocator remote = null;

remote = (RemoteServerLocator)method.invoke(myClass,null);

return remote.getHome(jndiHomeName,className);

}

private ServerLocatorAdapter() {

// 為cache提供線程安全的保證

cache = Collections.synchronizedMap(new HashMap());

}}

其中Resource為資源類，其中通過對(duì)配置文件的讀取，取得一些指定的配置信息。

RemoteServerLocator和LocalServerLocator是兩個(gè)根據(jù)不同的調(diào)用方式取得home借口的具體實(shí)現(xiàn)類，代碼如下:

LocalServerLocator：

import javax.naming.*;

import javax.rmi.PortableRemoteObject;

import java.util.*;

import javax.ejb.*;

public class LocalServerLocator {

private Context ic;

private Map cache;//緩存home

private static LocalServerLocator me;

public static LocalServerLocator getInstance()

{if(me == null)

{try

{me = new LocalServerLocator();

}

catch(Exception e)

{System.err.println(e.getCause());

System.err.println(e.getMessage());

}}

return me;

}

public EJBLocalHome getLocalHome(String jndiHomeName, Class className) throws Exception {

EJBLocalHome home = null;

try {if (cache.containsKey(jndiHomeName)) {

home = (EJBLocalHome) cache.get(jndiHomeName);

} else {

Object objref = ic.lookup(jndiHomeName);

home = (EJBLocalHome) objref;

cache.put(jndiHomeName, home);

}

} catch (NamingException ne) {

System.err.println(jndiHomeName);

throw ne;

} catch (Exception e) {

throw e;

}

return home;

}

private LocalServerLocator() throws Exception{

try

{

ic = new InitialContext();

// 為cache提供線程安全的保證

cache = Collections.synchronizedMap(new HashMap());

}

catch(NamingException ne)

{

throw ne;

}

catch(Exception e)

{

throw e;

}

}}