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运用反射实现ejb动态委派

时间:2009-12-23 15:42来源:未知 作者:admin 点击:
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每个bean可能会有很多方法,一般我们通过一个delegate来调用sessionbean中的方法,而非直接调用sessionbean,delegate中只是简单的对每个相对应的sessionbean的public方法的简单封装,在调用的时候

  每个bean可能会有很多方法,一般我们通过一个delegate来调用sessionbean中的方法,而非直接调用sessionbean,delegate中只是简单的对每个相对应的sessionbean的public方法的简单封装,在调用的时候省去了每次对home的查找和ejb对象的create,但是可能我们的bean会有很多方法,假如每个bean都写这样一个delegate,这样工作量就会很大,而且也不便于以后系统的移植,比如说,原来使用ejb实现,现在要改用jdo直接操作数据库,而通过运用Java的reflect技术,就能较好地实现这些要求。首先,定义了一个FacadeDelegate的抽象类,用来实现对sessionbean的home的查找,代码如下:
  
  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是一个用来根据是local还是remote调用ejb对象而通过不同的方法查找home的类,假如type为local则调用LocalServerLocate中的方法,假如type为remote则调用RemoteServerLocate中的方法,获得home。代码如下:
  
  import java.util.*;
  
  import java.lang.reflect.*;
  
  import testejb.util.resource.*;
  
  public class ServerLocatorAdapter {
  
   private Map cache;//用来缓存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() {
  
  // 为cache提供线程安全的保证
  
  cache = Collections.synchronizedMap(new HashMap());
  
   }
  
  }
  
  其中Resource为资源类,其中通过对配置文件的读取,取得一些指定的配置信息。
  
  RemoteServerLocator和LocalServerLocator是两个根据不同的调用方式取得home借口的具体实现类,代码如下:
  
  LocalServerLocator:
  
  import javax.naming.*;
  
  import javax.rmi.PortableRemoteObject;
  
  import java.util.*;
  
  import javax.ejb.*;
  
  public class LocalServerLocator {
  
   private Context ic;
  
   private Map cache;//缓存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();
  
   // 为cache提供线程安全的保证
  
   cache = Collections.synchronizedMap(new HashMap());
  
  }
  
  catch(NamingException ne)
  
  {
  
   throw ne;
  
  }
  
  catch(Exception e)
  
  {
  
   throw e;
  
  }
  
   }
  
  }
  
  RemoteServerLocator
  
  import javax.naming.*;
  
  import javax.rmi.PortableRemoteObject;
  
  import java.util.*;
  
  import javax.ejb.*;
  
  public class RemoteServerLocator{
  
   private Context ic;
  
   private Map cache;
  
   private static RemoteServerLocator me;
  
   public static RemoteServerLocator getInstance()
  
   {
  
  if(me == null)
  
  {
  
   try
  
   {
  
  me = new RemoteServerLocator();
  
   }
  
   catch(Exception e)
  
   {
  
  System.err.println(e.getMessage());
  
   }
  
  }
  
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