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每個(gè)bean可能會(huì)有很多方法，一般我們通過(guò)一個(gè)delegate來(lái)調(diào)用sessionbean中的方法，而非直接調(diào)用sessionbean,delegate中只是簡(jiǎn)單的對(duì)每個(gè)相對(duì)應(yīng)的sessionbean的public方法的簡(jiǎn)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，如果每個(gè)bean都寫(xiě)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(shuō)，原來(lái)使用ejb實(shí)現(xiàn)，現(xiàn)在要改用jdo直接操作數(shù)據(jù)庫(kù)，而通過(guò)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(lèi)，用來(lái)實(shí)現(xiàn)對(duì)sessionbean的home的查找,代碼如下：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是一個(gè)用來(lái)根據(jù)是local還是remote調(diào)用ejb對(duì)象而通過(guò)不同的方法查找home的類(lèi)，如果type為local則調(diào)用LocalServerLocate中的方法，如果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(lái)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(xiàn)程安全的保證
cache = Collections.synchronizedMap(new HashMap());
}
}
其中Resource為資源類(lèi)，其中通過(guò)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(lèi)，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(xiàn)程安全的保證
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();
// 為cache提供線(xiàn)程安全的保證
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);
}
}
對(duì)上面這些調(diào)用機(jī)制有個(gè)了解之后，下面就是來(lái)具體的實(shí)現(xiàn)動(dòng)態(tài)委派了，再此定義了一個(gè)FacadeDelegateImp類(lèi)，繼承了FacadeDelegate類(lèi)。先看一下代碼，然后對(duì)此作解釋?zhuān)@樣比較清楚一些
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方法是在調(diào)用invoke之前對(duì)要調(diào)用的sessionbean進(jìn)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));//調(diào)用父類(lèi)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);//調(diào)用home的//create方法，取得ejbObject
methodMap = new HashMap();
//將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方法是對(duì)一般java類(lèi)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“怎么運(yùn)用反射實(shí)現(xiàn)ejb動(dòng)態(tài)委派”這篇文章的所有內(nèi)容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內(nèi)容對(duì)大家有所幫助，如果還想學(xué)習(xí)更多知識(shí)，歡迎關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道！
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