public class Person {
private String name;
private int age;
public Person(String name,int age) {
super();
this.name = name;
this.age = age;
}
public Person(){}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}
public void show()
{
System.out.println("show");
}
public void fun(String str)
{
System.out.println(str);
}
public static void function()
{
System.out.println("static");
}
}
public class Demo1 {
/**
* 反射：动态获取字节码文件对象(Person.class)，并对其成员进行运行
*
* 动态获取字节码文件对象的方式：
* 1：任何一个对象都是由字节码文件对象创建的，所以任何一个对象都可以得到自己的字节码文件对象
* 那么这个功能应该定义在Object中，所以使用 getClass()
* 需要先new对象
*
* 2:每种数据类型都有一个 静态的class 属性,通过该属性可以得到字节码文件对象
* 不需要new对象，但是需要Person类存在
*
* 3:Class类提供了一个静态的forName(String str)方法
* 只需要提供字符串形式的包名+类名
* @throws ClassNotFoundException
*/
public static void main(String[] args) throws ClassNotFoundException {
getClaz();
getClaz2();
getClaz3();
}
//Class类提供了一个静态的forName
public static void getClaz3() throws ClassNotFoundException
{
Class<?> claz1 = Class.forName("com.qianfeng.reflect.Person");
Class<?> claz2 = Class.forName("com.qianfeng.reflect.Person");
System.out.println(claz1==claz2);
}
//通过静态属性class获取字节码文件对象
public static void getClaz2()
{
Class<Person> claz1 = Person.class;
Class<Person> claz2 = Person.class;
System.out.println(claz1==claz2);
}
//1:使用Object中的 getClass()获取字节码文件对象
public static void getClaz()
{
// Person person1 = new Person();//先加载Person.class到方法区
// Class<? extends Person> claz1 = person1.getClass();//得到了 Person.class
//
// Person person2 = new Person();
// Class<? extends Person> claz2 = person2.getClass();//得到了 Person.class
//
// System.out.println(claz1==claz2);//true
}
}
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class Demo2 {
/**
* 动态获取字节码文件对象，并创建对象
* @throws IllegalAccessException
* @throws InstantiationException
* @throws ClassNotFoundException
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws SecurityException
* @throws NoSuchMethodException
*/
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
createObj1();
createObj2();
}
//使用带参数的构造方法创建对象
public static void createObj2() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException
{ //Person person = new Person("小红",20);
//获取字节码文件对象---Person.class
Class<?> claz = Class.forName("com.qianfeng.reflect.Person");
//得到构造方法所属的Constructor类型的对象
Constructor<?> constructor = claz.getConstructor(String.class,int.class);
//使用构造方法创建对象--使用Constructor提供的创建对象的功能
Person person =(Person)constructor.newInstance("小红",20);
System.out.println(person);
}
//当空参的构造方法不存在时，会发生InstantiationException
//当构造方法的权限过低时，会发生IllegalAccessException
public static void createObj1() throws ClassNotFoundException, InstantiationException, IllegalAccessException
{
//Person person = new Person();
//获取字节码文件对象---Person.class
Class<?> claz = Class.forName("com.qianfeng.reflect.Person");
//使用Class提供的newInstance()方法创建Person类型的对象
Object obj = claz.newInstance();//使用空参的构造方法创建对象
Person person = (Person)obj;
System.out.println(person);
}
}
import java.lang.reflect.Field;
public class Demo3 {
/**
* 动态创建对象并给属性赋值
* @throws ClassNotFoundException
* @throws SecurityException
* @throws NoSuchFieldException
* @throws IllegalAccessException
* @throws InstantiationException
*/
public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, SecurityException, InstantiationException, IllegalAccessException {
//Person person = new Person();
//person.setName("小红");
//获取字节码文件对象---Person.class
Class<?> claz = Class.forName("com.qianfeng.reflect.Person");
//得到属性name所属的 Field类型的对象
//Field field = claz.getField("name");//只能获取权限是public 的属性
//System.out.println(field);//NoSuchFieldException
Field field = claz.getDeclaredField("name");
//因为name是非静态属性，所以必须通过对象访问，所以先创建对象
Object obj = claz.newInstance();
//设置name属性为可访问的
field.setAccessible(true);// 该方法是从父类中继承的
//使用Field类提供的赋值功能，给属性赋值
field.set(obj, "小红");
System.out.println(obj);
}
}
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Demo4 {
/**
* 动态创建对象，并调用方法
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws IllegalAccessException
* @throws InstantiationException
* @throws SecurityException
* @throws NoSuchMethodException
* @throws ClassNotFoundException
*/
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
method1();
method2();
method3();
}
//调用静态方法
public static void method3() throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException
{
//获取字节码文件对象---Person.class
Class<?> claz = Class.forName("com.qianfeng.reflect.Person");
///获取被调用的方法所属的 Method类型的对象
Method method = claz.getMethod("function", null);
//执行方法
method.invoke(null, null);
}
//调用带参的构造方法
public static void method2() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException
{
//获取字节码文件对象---Person.class
Class<?> claz = Class.forName("com.qianfeng.reflect.Person");
//获取被调用的方法所属的 Method类型的对象
Method method = claz.getMethod("fun", String.class);
//fun()属于非静态方式，需要对象去调用
Object obj = claz.newInstance();
//执行方法
method.invoke(obj, "hello");
}
//调用无参的构造方法
public static void method1() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException
{
// Person person = new Person();person.show();
//获取字节码文件对象---Person.class
Class<?> claz = Class.forName("com.qianfeng.reflect.Person");
//获取被调用的方法所属的 Method类型的对象
Method method = claz.getMethod("show", null);
//show()属于非静态方式，需要对象去调用
Object obj = claz.newInstance();
//执行方法
method.invoke(obj, null);
}
}
版权声明：本文为博主原创文章，未经博主允许不得转载。
原文地址：http://blog.csdn.net/bluezhangfun/article/details/47983547
