JAVA反射

动态调用方法

public class Ref {
	/**
	* @param message
	*/
	public Ref(String message){
		System.out.println("Hello :" + message);
	}
	
	public void sayHello(String message){
		System.out.println("Say Hello!" + message);
	}
	
	public static String show(){
		return "static show()";
	}
	
	public static void main(String[] args) 
		throws SecurityException, NoSuchMethodException, 
		ClassNotFoundException, IllegalArgumentException, 
		InstantiationException, IllegalAccessException, 
		InvocationTargetException{

		//得到Ref类c(元数据)
		Class c = Class.forName("test.Ref");
		//通过指定参数类型获取相应构造函数(对象)
		Constructor constructor = c.getConstructor(String.class);
		//通过构造函数实例化Ref类对象test
		Ref test =(Ref)constructor.newInstance("Test Instructor");

		//通过指定的方法名称取得对应方法对象
		//*****************
		//语法: 类名.getMethod("方法名称",形参类型列表)
		//*****************
		Method method = c.getMethod("sayHello", String.class);
		
		//动态调用方法(非静态方法)
		//*****************
		//语法: method.invoke(对象实例, 实参列表);
		//*****************
		method.invoke(test, "Test method");
		
		//动态调用方法(静态方法)
		Method show = c.getMethod("show");
		String str = (String)show.invoke(test);  //静态方法调用方式1
		//String str = (String)show.invoke(null);//静态方法调用方式2
		System.out.println (str);
	}
}

 接口应用子对象

 

interface XY{
	public void show();
}
class X implements XY{
	public void show(){
		System.out.println ("X Class");
	}
}
class Y implements XY{
	public void show(){
		System.out.println ("Y Class");
	}
}
public class Reflect{
  static public void main(String[] args){
  	try{
  		Class c = Class.forName("Y");//X
  		XY t = (XY)c.newInstance();  //反射相应的一个子类对象
  		t.show();  //动态运行不同类的方法
  		X x = new X(); //X Class
  		Class xc = Class.forName("X");
  		System.out.println (xc.isInstance(x));//true
  		System.out.println (t instanceof XY); //true
  		System.out.println (t instanceof X); //true
  		System.out.println (t instanceof Y);//false
  	}catch(Exception e){}
  }
}

   反射类成员

 

import java.lang.reflect.*;
public class ReflectDemo{
  public static void main(String[] args){
  	try{
  		/*得到该类的所有数据字段*/
  		String className = "Student";
  		Class c = Class.forName(className);
  		showFields(c); //显示该类所有属性信息
  		showConstructors(c); //显示所有构造方法
  		showMethods(c);//显示该类所有方法信息
  	}catch(Exception e){
  		e.printStackTrace();
  	}
  }
  /*得到该类的所有数据字段*/ 
  public static void showFields(Class c){ 
  	Field fields[] = c.getDeclaredFields();
		for(Field f : fields){
			//1./*数据字段修饰符*/
			String m =Modifier.toString(f.getModifiers());
			//2./*字段数据类型名*/
			Class type=f.getType(); String t =type.getName();
			//3./*类的属性名称*/
			String n = f.getName();
			System.out.println (m+" "+t+" "+n);
		}
	}
	/*得到构造器*/
	public static void showConstructors(Class c){  
		Constructor[] cons=c.getDeclaredConstructors(); 
		for(Constructor con : cons){
			String m = Modifier.toString(con.getModifiers());
			String n = con.getName();
			System.out.print (m+" "+n+"(");
			Class[] params = con.getParameterTypes();
			for(int j=0;j<params.length; j++){
				if(j==params.length-1){					
					System.out.print (params[j].getSimpleName());
				}else
					System.out.print (params[j].getSimpleName()+",");
			}
			System.out.println (")");
		} 
	}
	/*得到类里所有方法*/
	public static void showMethods(Class c){ 
		Method[] m=c.getMethods(); 
		for(int i=0; i<m.length; i++){
			/*方法修饰符*/
			String modify = Modifier.toString(m[i].getModifiers());
			System.out.print(modify + " ");
			/*方法返回类型*/
			Class returntype=m[i].getReturnType();
			System.out.print(returntype.getName()+" ");
			/*方法名称*/ 
			String name = m[i].getName(); 
			System.out.print(name + "(");
			/*方法参数*/
			Class[] params = m[i].getParameterTypes();
			for(int j=0;j<params.length; j++){
				if(j==params.length-1){					
					System.out.print (params[j].getSimpleName());
				}else
					System.out.print (params[j].getSimpleName()+",");
			}
			System.out.println (")");
		}  
	} 
}

  student.java

 

public class Student{
	public String name = "";
	public int age = 0;
	public Student(){}
	public Student(String name, int age){
		this.name = name;
		this.age = age;
	}
	public void show(){
		System.out.println ("反射测试."+this.name);
	}
}