15.4 Java反射机制的深入应用(血干JAVA系类)

15.4 Java反射机制的深入应用

• 15.4.1通过反射调用类中的方法
• • • • 【例15.14】调用Person类中的sayChina()方法
      • 【例15.15］调用Person类中的sayHello()方法
• 15.4.2 调用 setter 及 getter 方法
• • • • 【例15.16］调用setter及getter方法
• 15.4.3通过反射操作属性
• 15.4.4通过反射操作数组
• • • • 【例15.18］取得数组信息并修改数组内容
      • 【例15.19］修改数组的大小

15.4.1通过反射调用类中的方法

			Method met = c.getMethod("sayChina");
			met.invoke(c.newInstance());

【例15.14】调用Person类中的sayChina()方法

public class demo {

	public static void main(String[] args) throws Exception
	{
		Class c = null;
		try 
		{
			c = Class.forName("file.Person");//实例化Class
		} 
		catch (ClassNotFoundException e) 
		{
			e.printStackTrace();
		}
		
		
		try 
		{
			Method met = c.getMethod("sayChina");
			met.invoke(c.newInstance());
		} 
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}
}

【例15.15］调用Person类中的sayHello()方法

public class demo {

	public static void main(String[] args) throws Exception
	{
		Class c = null;
		try 
		{
			c = Class.forName("file.Person");//实例化Class
		} 
		catch (ClassNotFoundException e) 
		{
			e.printStackTrace();
		}
		
		
		try 
		{
			
			Method met = c.getMethod("sayHello",String.class,int.class);
			String str = (String)met.invoke(c.newInstance(),"李四",30);
			System.out.println(str);
		} 
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}
}

15.4.2 调用 setter 及 getter 方法

【例15.16］调用setter及getter方法

setter(Object obj,String att,Object value,Class type)
getter(Object obj,String att)
为什么是Object类型，方便传入不同的实例对象，不同类型的数值

public class demo {

	public static void main(String[] args) throws Exception
	{
		Class c = null;
		try 
		{
			c = Class.forName("file.Person");//实例化Class
		} 
		catch (ClassNotFoundException e) 
		{
			e.printStackTrace();
		}
		Object obj = null;
		try 
		{
			obj =  c.newInstance();
		}
		catch (Exception e) 
		{
			e.printStackTrace();
		}
		setter(obj,"name","李华",String.class);
		setter(obj,"age",22,int.class);
		System.out.print("name:");
		getter(obj,"name");
		System.out.print("age:");
		getter(obj,"age");
		
	}
	
	public static void setter(Object obj,String att,Object value,Class type)
	{
		try 
		{
			Method met = obj.getClass().getMethod("set"+sub(att),type);
			met.invoke(obj, value);
		}
		catch (Exception e) 
		{
			e.printStackTrace();
		}
	}
	
	
	public static void getter(Object obj,String att)
	{
		try
		{
			Method met = obj.getClass().getMethod("get"+sub(att));
			System.out.println(met.invoke(obj));
		}
		catch (Exception e) 
		{
			e.printStackTrace();
		}
	}
	
	
	
	public static String sub(String att)
	{
		return att.substring(0, 1).toUpperCase() + att.substring(1);
	}
}

15.4.3通过反射操作属性

public class demo {

	public static void main(String[] args) throws Exception
	{
		Class c = null;
		try 
		{
			c = Class.forName("file.Person");//实例化Class
		} 
		catch (ClassNotFoundException e) 
		{
			e.printStackTrace();
		}
		Object obj = null;
		try 
		{
			obj =  c.newInstance();
		}
		catch (Exception e) 
		{
			e.printStackTrace();
		}
		//获取本类属性
		Field nameField = c.getDeclaredField("name");
		Field ageField = c.getDeclaredField("age");
		//设置权限
		nameField.setAccessible(true);
		ageField.setAccessible(true);
		//set		
		nameField.set(obj,"李四");
		ageField.set(obj,32);
		//get
		System.out.println(nameField.get(obj));
		System.out.println(ageField.get(obj));	
	}
}

15.4.4通过反射操作数组

【例15.18］取得数组信息并修改数组内容

public class demo {

	public static void main(String[] args) throws Exception
	{
		int temp[] = {1,2,3};
		Class c = temp.getClass().getComponentType();
		System.out.println("类型："+c.getName());
		System.out.println("长度："+Array.getLength(temp));
		System.out.println("第一个："+Array.get(temp, 0));
		Array.set(temp, 0, 11);
		System.out.println("第一个："+Array.get(temp, 0));		
	}
}

【例15.19］修改数组的大小

Class c = obj.getClass();//Class实例
Class arr = c.getComponentType();//array实例
//getComponentType()作用：返回数组类型

public class demo {

	public static void main(String[] args) throws Exception
	{
		int temp[] = {1,2,3};
		int newTemp[] = (int[])arrayinc(temp,5) ;
		print(newTemp);
		System.out.println("----------------------------");
		String str[] = {"str1","str2","str3","str4"};
		String newstr[] = (String[])arrayinc(str, 8);
		print(newstr);
	}
	public static Object arrayinc(Object obj,int len) 
	{
		Class c = obj.getClass();//Class实例
		Class arr = c.getComponentType();//array实例
		Object newO = Array.newInstance(arr, len);//实例化新数组（数组类型，长度）
		int co = Array.getLength(obj);
		System.arraycopy(obj, 0, newO, 0, co);
		return newO;
	}
	
	public static void print(Object obj)
	{
		
		Class c = obj.getClass();
		if(!c.isArray())return ;
		Class arrtype = c.getComponentType();
		int len = Array.getLength(obj);
		System.out.println("类型："+arrtype.getName()+",长度:"+len);
		for(int i=0;i
			System.out.print(Array.get(obj, i)+" ");
		}
		System.out.println();
	}
}