Java反射机制

反射机制原理图如下：

以下是例子：

package com.jinzhi.test1;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Demo3 {
 public static void main(String[] args) {
  //利用反向加载的机制来通过类名自动调用它的方法，和属性
  //得到JVM中class文件的类Class:3种方法
  Class c1 = Student.class;
  Class c2 = new Student().getClass();
  try {
   Class c3 = Class.forName("com.jinzhi.test1.Student");
  } catch (ClassNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  //调用无参构造方法-Constructor
  Student s1 = null;
  try {
   s1 = (Student)c1.newInstance();
  } catch (InstantiationException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalAccessException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  s1.setName("周星驰");
  s1.setAge(24);
  s1.setSex("男");
  System.out.println(s1.getName() + " / " + s1.getSex() + " / " + s1.getAge());
  System.out.println("------------------------------------------");
  //调用类的无参构造
  //得到构造方法
  try {
   Constructor c = c1.getConstructor(String.class, int.class, String.class);
   Student s2 = (Student)c.newInstance("路飞", 24, "男");
   System.out.println(s2.getName()+"/" + s2.getAge() +"/"+ s2.getSex());
   System.out.println("------------------------------------------");
  } catch (NoSuchMethodException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (SecurityException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (InstantiationException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalAccessException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalArgumentException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (InvocationTargetException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  
  //得到类的属性
  try {
   Field f = c1.getDeclaredField("name");
   Student s3 = (Student)c1.newInstance();
   //还要设置私有属性可访问的属性
   //f.setAccessible(true);
   f.set(s3, "男神");
   System.out.println("我的姓名  " + s3.getName());
   System.out.println("-------------------------------");
  } catch (NoSuchFieldException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (SecurityException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (InstantiationException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalAccessException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalArgumentException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  //得到一般方法
  try {
   Method m = c1.getDeclaredMethod("setName", String.class);
   Student s4 = (Student)c1.newInstance();
   //设置私有方法可访问的特性
   m.setAccessible(true);
   m.invoke(s4, "司马光");
   System.out.println("姓名：" + s4.getName());
  } catch (NoSuchMethodException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (SecurityException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (InstantiationException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalAccessException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IllegalArgumentException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (InvocationTargetException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }

}