浅谈Java反射与代理

User user = new User();
user.setTime5Flag("test");
 
Class<?> cls = Class.forName("com.test.User");
//接口必须public,无论是否在本类内部使用！或者使用cls.getDeclaredMethod()，或者遍历修改可访问性
Method method = cls.getMethod("getTime5Flag");
String res1 = (String) method.invoke(user);
System.out.println(res1);
//涉及到基本类型如int，则使用int.class！Integer.class!=int.class！
method = cls.getMethod("setTime5Flag", String.class); 
method.invoke(user, "Rollen");
method = cls.getMethod("getTime5Flag");
String res2 = (String) method.invoke(user);
System.out.println(res2);

user.getClass().getName();//全路径类名
user.getClass().getSimpleName();//无包名的类名

Class.forName("com.test.User");
com.test.User.class;
user.getClass();

User user = (User) cls.newInstance();//必须有无参构造函数

Constructor<?> cons[]=cls.getConstructors(); //按声明顺序返回
cons[0].newInstance();//无显示声明，则有默认构造函数

Class<?> intes[] = cls.getInterfaces();

cls.getSuperClass();

int mo = cls.getModifiers();
int mo = cons[0].getModifiers();
int mo = method.getModifiers();
Modifier.toString(mo);

method.getParametors();
cons[0].getParametors();

method.getParametorTypes();
cons[0].getParametorTypes();

method.getExceptionTypes();

Field[] field = cls.getDeclaredFields(); //包括private
field[0].getModifiers();
field[0].getType();

cls.getFields();

field.setAccessible(true);
field.set(obj,'ces');
field.get(obj);

int[] temp={1,2,3,4,5};
Class<?> demo = temp.getClass().getComponentType();
System.out.println("数组类型： "+demo.getName());//int
System.out.println("数组长度： "+Array.getLength(temp));//5
System.out.println("数组的第一个元素： "+Array.get(temp, 0));//1
Array.set(temp, 0, 100);
System.out.println("修改之后数组第一个元素为： "+Array.get(temp, 0));//100

cls.getComponentType();

cls.isArray();

public interface Count { 
  public void queryCount();
}
public class CountImpl implements Count {
  public void queryCount() { 
    System.out.println("查看账户方法...");
  }
}
//代理类
public class CountProxy implements Count { 
  private CountImpl countImpl;  
  public CountProxy(CountImpl countImpl) { 
    this.countImpl = countImpl; 
  }  
  @Override 
  public void queryCount() { 
    System.out.println("事务处理之前");      
    countImpl.queryCount(); // 调用委托类的方法;
    System.out.println("事务处理之后"); 
  }
｝ 
//测试类
public class TestCount { 
  public static void main(String[] args) { 
    CountImpl countImpl = new CountImpl(); 
    CountProxy countProxy = new CountProxy(countImpl); 
    countProxy.queryCount();  
  } 
｝

interface Subject {
  public String say(String name, int age);
}
class RealSubject implements Subject {
  @Override
  public String say(String name, int age) {
    return name + " " + age;
  }
}
//JDK动态代理类
class MyInvocationHandler implements InvocationHandler {
  private Object target = null;
  //绑定委托对象并返回一个代理类
  public Object bind(Object target) {
    this. target = target;
    return Proxy.newProxyInstance(target.getClass().getClassLoader(),
　　　　　　　　　　target.getClass().getInterfaces(), this); //要绑定接口（cglib弥补了这一点）
  }
  @Override
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    System.out.println(“before method!”);
    Object temp = method.invoke(target, args);
    System.out.println(“after method!”);
    return temp;
  }
}
class hello {
  public static void main(String[] args) {
    MyInvocationHandler demo = new MyInvocationHandler();
    Subject sub = (Subject) demo.bind(new RealSubject());
    String info = sub.say("Rollen", 20);
    System.out.println(info);
  }
}

public interface BookFacade { 
  public void addBook(); 
} 
public class BookFacadeImpl1 { 
  public void addBook() { 
    System.out.println("增加图书的普通方法..."); 
  } 
} 
 
import java.lang.reflect.Method;  
import net.sf.cglib.proxy.Enhancer; 
import net.sf.cglib.proxy.MethodInterceptor; 
import net.sf.cglib.proxy.MethodProxy; 
//cglib动态代理类
public class BookFacadeCglib implements MethodInterceptor { 
  private Object target;  
  //绑定委托对象并返回一个代理类
  public Object getInstance(Object target) { 
    this.target = target; 
    Enhancer enhancer = new Enhancer(); 
    enhancer.setSuperclass(this.target.getClass()); 
    // 回调方法 
    enhancer.setCallback(this); 
    // 创建代理对象 
    return enhancer.create(); 
  }  
  @Override 
  // 回调方法 
  public Object intercept(Object obj, Method method, Object[] args, 
      MethodProxy proxy) throws Throwable { 
    System.out.println("事物开始"); 
    Object temp = proxy.invokeSuper(obj, args); 
    System.out.println("事物结束"); 
    return temp;  
  } 
} 
public class TestCglib {
  public static void main(String[] args) { 
    BookFacadeCglib cglib = new BookFacadeCglib(); 
    BookFacadeImpl1 bookCglib = (BookFacadeImpl1)cglib.getInstance(new BookFacadeImpl1()); 
    bookCglib.addBook(); 
  } 
}