通過反射實現(xiàn)Java下的委托機制代碼詳解

public Class Delegater()//空參構造，該類管理委托實例并實現(xiàn)委托方法 
//添加一個靜態(tài)方法委托，返回整型值ID代表該方法與參數(shù)構成的實例。若失敗，則返回-1。 
public synchronized int addFunctionDelegate(Class<?> srcClass,String methodName,Object... params);
//添加一個實例方法委托，返回整型值ID代表該方法與參數(shù)構成的實例。若失敗，則返回-1。 
public synchronized int addFunctionDelegate(Object srcObj,String methodName,Object... params);
//根據(jù)整型ID從委托實例中刪除一個方法委托,返回是否成功 
public synchronized Boolean removeMethod(int registerID);
//依次執(zhí)行該委托實例中的所有方法委托（無序） 
public synchronized void invokeAllMethod();
//將參數(shù)表轉換為參數(shù)類型表 
private Class<?>[] getParamTypes(Object[] params);
//由指定的Class、方法名、參數(shù)類型表獲得方法實例 
private Method getDstMethod(Class<?> srcClass,String methodName,Class<?>[] paramTypes);
class DelegateNode(Method refMethod,Object[] params)//DelegateNode類在不使用Object構造時敘述了一個靜態(tài)方法委托，包括方法實例及參數(shù)表 
class DelegateNode(Object srcObj,Method refMethod,Object[] params)//DelegateNode類在使用Object構造時敘述了一個實例方法委托，包括類實例、方法實例及參數(shù)表 
public void invokeMethod();
//執(zhí)行該節(jié)點敘述的方法委托

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Hashtable;
/**Delegater類使用RTTI及反射實現(xiàn)Java下的委托機制 
 * @author 三向板磚 
 * */
public class Delegater {
	static int register = Integer.MIN_VALUE;
	//ID分配變量 
	Hashtable<Integer,DelegateNode> nodeTable;
	//管理ID與對應委托的容器 
	public Delegater() 
	  {
		nodeTable = new Hashtable<Integer,DelegateNode>();
	}
	//添加靜態(tài)方法委托 
	public synchronized int addFunctionDelegate(Class<?> srcClass,String methodName,Object... params) 
	  {
		Class<?>[] paramTypes = getParamTypes(params);
		Method refMethod;
		if((refMethod = getDstMethod(srcClass,methodName,paramTypes)) != null) 
		    {
			register++;
			nodeTable.put(register,new DelegateNode(refMethod, params));
			return register;
		} else 
		    {
			return -1;
		}
	}
	//添加動態(tài)方法委托 
	public synchronized int addFunctionDelegate(Object srcObj,String methodName,Object... params) 
	  {
		Class<?>[] paramTypes = getParamTypes(params);
		Method refMethod;
		if((refMethod = getDstMethod(srcObj.getClass(),methodName,paramTypes)) != null) 
		    {
			register++;
			nodeTable.put(register,new DelegateNode(srcObj,refMethod, params));
			return register;
		} else 
		    {
			return -1;
		}
	}
	//刪除一個方法委托 
	public synchronized Boolean removeMethod(int registerID) 
	  {
		if(nodeTable.containsKey(registerID)) 
		    {
			nodeTable.remove(registerID);
			return true;
		}
		return false;
	}
	//無序地執(zhí)行委托方法 
	public synchronized void invokeAllMethod() 
	  {
		for (DelegateNode node:nodeTable.values()) 
		    {
			node.invokeMethod();
		}
	}
	//將參數(shù)表轉化為參數(shù)類型表 
	private Class<?>[] getParamTypes(Object[] params) 
	  {
		Class<?>[] paramTypes = new Class<?>[params.length];
		for (int i = 0;i < params.length;i++) 
		    {
			paramTypes[i] = params[i].getClass();
		}
		return paramTypes;
	}
	//根據(jù)Class類實例、方法名、參數(shù)類型表獲得一個Method實例 
	private Method getDstMethod(Class<?> srcClass,String methodName,Class<?>[] paramTypes) 
	  {
		Method result = null;
		try {
			result = srcClass.getMethod(methodName, paramTypes);
			if(result.getReturnType() != void.class) 
			      {
				System.out.println("Warning,Method:"+methodName+" has a return value!");
			}
		}
		catch (NoSuchMethodException | SecurityException e) {
			System.out.println("Can Not Found Method:"+methodName+",ensure it's exist and visible!");
		}
		return result;
	}
}
class DelegateNode 
{
	Object srcObj;
	Method refMethod;
	Object[] params;
	public DelegateNode(Method refMethod,Object[] params) 
	  {
		this.refMethod = refMethod;
		this.params = params;
	}
	public DelegateNode(Object srcObj,Method refMethod,Object[] params) 
	  {
		this.srcObj = srcObj;
		this.refMethod = refMethod;
		this.params = params;
	}
	public void invokeMethod() 
	  {
		try {
			refMethod.invoke(srcObj,params);
		}
		catch (IllegalAccessException | IllegalArgumentException 
		        | InvocationTargetException e) {
			System.out.println("Method:"+refMethod.toString()+" invoke fail!");
		}
	}
}

public class DelegaterTest {
	public void showInfo() 
	  {
		System.out.println("Hello Delegate!");
	}
	public void showCustomInfo(String info) 
	  {
		System.out.println(info);
	}
	public static void showStaticInfo() 
	  {
		System.out.println("Static Delegate!");
	}
	public static void showCustomStaticInfo(String info) 
	  {
		System.out.println(info);
	}
	public static void main(String[] args) {
		Delegater dele = new Delegater();
		DelegaterTest tester = new DelegaterTest();
		int ID = dele.addFunctionDelegate(tester,"showInfo");
		dele.addFunctionDelegate(tester,"showCustomInfo","Custom!");
		dele.addFunctionDelegate(DelegaterTest.class,"showStaticInfo");
		dele.addFunctionDelegate(DelegaterTest.class,"showCustomStaticInfo","StaticCustom!");
		dele.invokeAllMethod();
		dele.removeMethod(ID);
		System.out.println("------------------");
		dele.invokeAllMethod();
	}
}