怎么运用反射实现ejb动态委派

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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，如果每个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：XML:namespace prefix = o ns = "urn:schemas-microsoft-com:Office:office" />

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，如果type为local则调用LocalServerLocate中的方法，如果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());

  }

  }

  return me;

  }

  public EJBHome getHome(String jndiHomeName, Class className) throws Exception {

  EJBHome home = null;

  try {

  if (cache.containsKey(jndiHomeName)) {

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

  } else {

  Object objref = ic.lookup(jndiHomeName);

   Object obj = PortableRemoteObject.narrow(objref, className);

  home = (EJBHome) obj;

  cache.put(jndiHomeName, home);

  }

  } catch (NamingException ne) {

  System.err.println(jndiHomeName);

  throw ne;

  } catch (Exception e) {

  throw e;

  }

  return home;

  }

  private RemoteServerLocator() throws Exception{

  try {

  ic = getInitialContext();

  // 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;

  }

  }

  private javax.naming.Context getInitialContext() throws NamingException {

  java.util.Hashtable JNDIPaRM = new java.util.Hashtable();

  JNDIParm.put(Context.PROVideR_URL, "your server address");

  JNDIParm.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NaminGContextFactory");

  return new InitialContext(JNDIParm);

  }

}

对上面这些调用机制有个了解之后，下面就是来具体的实现动态委派了，再此定义了一个FacadeDelegateImp类，继承了FacadeDelegate类。先看一下代码，然后对此作解释，这样比较清楚一些

import testejb.delegate.common.*;

import javax.ejb.*;

import java.lang.reflect.*;

import java.util.*;

public class FacadeDelegateImp extends FacadeDelegate {

  private static FacadeDelegateImp me;

  private Map cache;

  private HashMap methodMap;

  private Object object;

  public static FacadeDelegateImp getInstance()

  {

  if(me == null)

  me = new FacadeDelegateImp();

  return me;

}

//init方法是在调用invoke之前对要调用的sessionbean进行初始化

  public void init(String jindiName, String className) {

  EJBHome home = null;

  if(cache.containsKey(jindiName))

  home = (EJBHome)cache.get(jindiName);

  else

  {

  try

  {

  home = super.getHome(jindiName, Class.forName(className));//调用父类的的方法取得home

  }

  catch(Exception e)

  {

  System.err.println(e.getMessage());

  }

  cache.put(jindiName,className);

  }

  try

  {

  object = home.getClass().getMethod("create", null).invoke(home, null);//调用home的//create方法，取得ejbObject

  methodMap = new HashMap();

//将ejbObject中所有的方法存入methodMap中

  Method[] aryMethod = object.getClass().getMethods();

  if(aryMethod != null && aryMethod.length > 0)

  {

  for (int i = 0; i < aryMethod.length; i++) {

  methodMap.put(aryMethod[i].getName(), aryMethod[i]);

  }

  }

  }

  catch(Exception e)

  {

  System.err.println(e.getMessage());

  }

  }

  //此init方法是对一般java类初始化

  public void init(String className,Object[] args)

  {

  boolean flage = false;

  if(cache.get(className) != null)

  object = cache.get(className);

  else

  {

  try {

  Class myClass = Class.forName(className);

  if (args != null && args.length > 0) {

  Class[] type = new Class[args.length];

  for (int i = 0; i < type.length; i++) {

  type[i] = args[i].getClass();

  }

  Constructor constructor = myClass.getConstructor(type);

  object = constructor.newInstance(args);

  cache.put(className, object);

  }

  else {

  object = myClass.newInstance();

  cache.put(className, object);

  }

  }

  catch (Exception e) {

  System.err.println(e.getMessage());

   }

  }

  Method[] methods = object.getClass().getMethods();

  methodMap = new HashMap();

  for(int i = 0; i< methods.length; i++)

  methodMap.put(methods[i].getName(),methods[i]);

  }

  public Object invoke(String method, Object[] args,String jindiName, String className)

  {

  if("init".equals(method))

  {

  this.init(jindiName, className);

  return null;

  }

  if(methodMap == null)

  this.init(jindiName, className);

  Method tmpMethod = (Method)methodMap.get(method);

   if(tmpMethod != null)

  {

  try

  {

  return tmpMethod.invoke(object, args);

  }

  catch(Exception e)

  {

  System.err.println(e.getMessage());

  }

  }

  return null;

  }

  public Object invoke(String method, Object[] args, String className)

  {

  if("init".equals(method))

  {

  this.init(className,args);

  return null;

  }

  if(methodMap == null)

  System.err.println("not init");

  Method tmpMethod = (Method)methodMap.get(method);

  if(tmpMethod != null)

  {

  try

  {

  return tmpMethod.invoke(object, args);

  }

  catch(Exception e)

  {

  System.err.println(e.getMessage());

  }

  }

  return null;

  }

  private FacadeDelegateImp() {

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

  }

}

以上是“怎么运用反射实现ejb动态委派”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注编程网精选频道！