设计模式

单例模式

1、配置文件读取类，协调系统整体行为
2、创建一个对象消耗资源过多
public class Singleton {
     private static Singleton singleton = null; 
     //限制产生多个对象
     private Singleton(){
     }  
     //通过该方法获得实例对象
     public static synchronized Singleton getSingleton(){
             if(singleton == null){
                    singleton = new Singleton();
             }
             return singleton;
     }
}

模板方法模式

工厂模式

代理模式

• 静态代理

public Interface IUserDao{
   public void eat();
}
public class UserDaoImpl implements IUserDao{
  public void eat(){
    //业务逻辑
  }
}
public class UserDaoProxy implements IUserDao{
  private IUserDao userDao;
  public UserDaoProxy(IUserDao userDao){
    this.userDao = userDao;
  }
  public void eat(){
    //修饰
    userDao.eat();
  }
}
main(){
  IUserDao userDao = new UserDaoProxy(new UserDaoImpl);
  userDao.eat();
}

• JDK动态代理

class MyHandler implements InvocationHandler{
  private Object target;
  public MyHandler(Object obj){
    this.target = obj;
  }
  public Object invoke(Object proxy, Method method, Object[] args){
    //加逻辑
    Object result = method.invoke(target, args);
  }
}
Interface IUserDao{
  void eat();
}
class UserDaoImpl implements IUserDao{
  void eat(){
    //业务逻辑
  }
}
main(){
  IUserDao userDao = new UserDaoImpl();
  MyHandler myHandler = new MyHandler(userDao);
  IUserDao userDao = Proxy.newProxyInstance(classloader, userDao.getClass().getInterfaces(), myHandler);
  userDao.eat();
}