代理模式

	静态代理
		接口
			public interface UserManager {
	
				public void addUser(String username, String password);
				
				public void modifyUser(int userId, String username, String password);
				
				public String findUserById(int userId);
			}
		实现类
			public class UserManagerImpl implements UserManager {

			public void addUser(String username, String password) {
		//		System.out.println("start-->>addUser - username=" + username + ", password=" + password);
		//		try {
		//			//
		//			System.out.println("UserManagerImpl.addUser()");
		//			System.out.println("end-->>addUser() ");
		//		}catch(Exception e) {
		//			e.printStackTrace();
		//			System.out.println("error-->>addUser() ");
		//		throw new java.lang.RuntimeException();
		//		}
				
				try {
					System.out.println("UserManagerImpl.addUser()");
				}catch(Exception e) {
					e.printStackTrace();
					throw new java.lang.RuntimeException();
				}	
				}

				public String findUserById(int userId) {
					System.out.println("UserManagerImpl.findUserById()");
					return null;
				}

				public void modifyUser(int userId, String username, String password) {
					System.out.println("UserManagerImpl.modifyUser()");
				}
			}
		
		代理
			public class UserManagerImplProxy implements UserManager {
	
				private UserManager userManager;
				
				public UserManagerImplProxy(UserManager userManager) {
					this.userManager = userManager;
				}
				
				public void addUser(String username, String password) {
					System.out.println("start-->>addUser - username=" + username + ", password=" + password);
					try {
						userManager.addUser(username, password);
						System.out.println("end-->>addUser() ");
					}catch(Exception e) {
						e.printStackTrace();
						System.out.println("error-->>addUser() ");
					}
				}

				public String findUserById(int userId) {
					return null;
				}

				public void modifyUser(int userId, String username, String password) {
				}
			}

		test
			public class Client {

				public static void main(String[] args) {
					//UserManager userManager = new UserManagerImpl();
					//userManager.addUser("张三", "123");
					
					UserManager userManager = new UserManagerImplProxy(new UserManagerImpl() );
					userManager.addUser("张三", "123");
				}

			}
		代理 和 实现 都实现了共同的接口
			代理在内部维护了一个实现，当调用代理的接口方法时，
			代理在内部调用了它维护的实现类的方法，并加上自己的操作
			静态代理需要一个个的写代理方法，不好用



	动态代理
		接口
			public interface UserManager {
	
				public void addUser(String username, String password);
				
				public void modifyUser(int userId, String username, String password);
				
				public String findUserById(int userId);
			}

		InvocationHandler
			public class LogHandler implements InvocationHandler {
	
				private Object targetObject;
				
				public Object newProxyObject(Object targetObject) {
					this.targetObject = targetObject;
					
					return Proxy.newProxyInstance(targetObject.getClass().getClassLoader(), 
							targetObject.getClass().getInterfaces(), this);
						
				}
				
				public Object invoke(Object proxy, Method method, Object[] args)
						throws Throwable {
					System.out.println("start-->>" + method.getName());
					for (int i=0; i<args.length; i++) {
						System.out.println(args[i]);
					}
					Object result = null;
					try {
						result = method.invoke(this.targetObject, args);
						System.out.println("end-->>" + method.getName());
					}catch(Exception e) {
						e.printStackTrace();
						System.out.println("error-->>" + method.getName());
					}
					System.out.println("result=" + result);
					return result;
				}

			}
		实现 
			public class UserManagerImpl implements UserManager {

				public void addUser(String username, String password) {
			//		System.out.println("start-->>addUser - username=" + username + ", password=" + password);
			//		try {
			//			//
			//			System.out.println("UserManagerImpl.addUser()");
			//			System.out.println("end-->>addUser() ");
			//		}catch(Exception e) {
			//			e.printStackTrace();
			//			System.out.println("error-->>addUser() ");
			//		throw new java.lang.RuntimeException();
			//		}
					
					try {
						System.out.println("UserManagerImpl.addUser()");
					}catch(Exception e) {
						e.printStackTrace();
						throw new java.lang.RuntimeException();
					}	
				}

				public String findUserById(int userId) {
					System.out.println("UserManagerImpl.findUserById()");
					return "李四";
				}

				public void modifyUser(int userId, String username, String password) {
					System.out.println("UserManagerImpl.modifyUser()");
				}
			}

		test
			public class Client {

				public static void main(String[] args) {
					//UserManager userManager = new UserManagerImpl();
					//userManager.addUser("张三", "123");
					
					//UserManager userManager = new UserManagerImplProxy(new UserManagerImpl() );
					//userManager.addUser("张三", "123");
					
					LogHandler handler = new LogHandler();
					UserManager userManager = (UserManager)handler.newProxyObject(new UserManagerImpl());
					//UserManagerImpl userManager = (UserManagerImpl)handler.newProxyObject(new UserManagerImpl());
					//userManager.addUser("张三", "123");
					//userManager.modifyUser(1, "张三", "123");
					userManager.findUserById(1);
				}

			}
		InvocationHandler中通过newProxyObject（）得到了一个实现了接口的代理，
			该代理能动态的代理接口中的方法，被代理对象只能时实现了接口的对象
			有第3方组件可以代理一般java对象