反射机制实在【运行状态】中，对于任意一个类，都能够知道这个类的所有属性和方法，对于任意一个对象，都能够调用它的任意一个方法和属性。
反射提供的功能：
在运行时判断任意一个对象所属的类，在运行时构造任意一个类的对象，在运行时判断任意一个类所具有的成员变量和方法，在运行时调用任意一个对象的方法，生成动态代理。
代码区：
接口1
package refelect;
public interface MyInterface {
void interfaceMethod();
}
接口2
package refelect;
public interface Myinterface02 {
void interface2Method();
}
类
package refelect;
public class Person implements MyInterface,Myinterface02{
private int id;
private String name;
private int age;
public String desc;
public void setId(int id) {
this.id = id;
}
private Person(String name){
this.name = name;
}
public void setName(String name) {
this.name = name;
}
public void setAge(int age) {
this.age = age;
}
public Person(){
}
public Person(int id) {
this.id = id;
}
public Person(int id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
@Override
public void interfaceMethod() {
System.out.println("interfaceMethod....");
}
public static void staticMethod(){
System.out.println("staticMethod");
}
private void privateMethod(){
System.out.println("privateMethod");
}
private void privateMethod(String name){
System.out.println("privateMethod" + name);
}
@Override
public void interface2Method() {
System.out.println("第二个接口中的方法！");
}
}
操作类
package refelect;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
public class ReflectDemo {
//通过反射来操作类
public static void TestClass(){
//获取反射对象（反射入口）:
// 获取Class的三种方法
// 第一种.Class.forName()
try {
Class aClass = Class.forName("refelect.Person");
System.out.println(aClass);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//第二种，类名.class
Class personClass = Person.class;
System.out.println(personClass);
//第三种，对象.class()
Person p = new Person();
Class pClass = p.getClass();
System.out.println(pClass);
}
//利用反射获取当前类的公共方法
public static void TestMethod(){
//Class入口
Class aClass = null;
try {
aClass= Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//获取所有的 公共 方法，
//所谓的公共方法，指的是本类，父类，以及接口中的所有方法
//符合访问权限修饰符规律，也就是public修饰的方法
Method[] methods = aClass.getMethods();
//遍历所有的公共方法
for (Method method: methods) {
System.out.println(method);
/*
* public java.lang.String refelect.Person.getName()
* 通过反射取出来的方法，会加上完整的包名
* 通过反射取方法，不仅仅取到了自己类中的方法，还取到了父类的方法，也就是Object类中的方法
* */
}
}
//获取所有的接口，java单继承多实现
public static void Demo03(){
//Class入口
Class aClass =null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//获取所有的接口
Class[] interfaces = aClass.getInterfaces();
//遍历接口
for (Class inter : interfaces) {
System.out.println(inter);
}
}
//通过反射来获取类的父类
public static void Demo04(){
//入口
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//java是单继承多实现，所以父类只有一个
Class superclass = aClass.getSuperclass();
System.out.println("Person的父类是：" + superclass);
}
//通过反射获取该类的所有构造方法
public static void Demo05(){
//入口
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//获取所有的构造方法
Constructor[] constructors = aClass.getConstructors();
for (Constructor con:constructors) {
System.out.println(con);
}
}
//通过反射获取所有的公共属性
public static void Demo06(){
//入口
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//获取所有的公共属性
//所谓的公共属性，指的是本类以及父类中的公共属性
//符合访问权限修饰符规律，也就是public修饰的成员变量
Field[] fields = aClass.getFields();
for (Field f:fields) {
System.out.println(f);
}
}
//通过反射获取当前类的所有方法，其中包含公共方法和私有方法,不包含父类和父接口
public static void Demo07(){
//入口
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
//获取当前类的所有方法，忽略访问权限修饰符的限制
Method[] declaredMethods = aClass.getDeclaredMethods();
for (Method me:declaredMethods) {
System.out.println(me);
}
}
//获取当前类的所有构造方法，忽略访问权限修饰符
public static void Demo08(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Constructor[] declaredConstructors = aClass.getDeclaredConstructors();
for (Constructor c:declaredConstructors) {
System.out.println(c);
}
}
//获取当前类的所有属性，忽略权限修饰符
public static void Demo09(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Field[] declaredFields = aClass.getDeclaredFields();
for (Field f:declaredFields) {
System.out.println(f);
}
}
//通过反射来new一个对象
public static void Demo10(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Object o = null;
try {
o = aClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
Person o1 = (Person) o;
o1.interfaceMethod();
}
//通过反射对对象中的属性赋值
public static void Demo11(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Object o = null;
try {
o = aClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
Person o1 = (Person) o;
o1.setName("路人甲");
o1.setAge(22);
System.out.println(o1.getName() + "今年" + o1.getAge());
}
//通过反射操作属性
public static void Demo12(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Object o = null;
try {
o = aClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
Person o1 = (Person) o;
Field name = null;
try {
name = aClass.getDeclaredField("name");
//访问的是private修饰的id，但是private是私有的
//所以我们需要修饰访问权限修饰符
//设置访问权限修饰符，将private改为public
name.setAccessible(true);
} catch (NoSuchFieldException e) {
e.printStackTrace();
}
try {
name.set(o1,"张三");
} catch (IllegalAccessException e) {
e.printStackTrace();
}
System.out.println(o1.getName());
}
//通过反射对私有方法进行调用
public static void Demo13(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Object o = null;
try {
o = aClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
Person o1 = (Person) o;
Method privateMethod = null;
try {
privateMethod = aClass.getDeclaredMethod("privateMethod", null);
privateMethod.setAccessible(true);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
try {
privateMethod.invoke(o1,null);//方法的调用通过invoke()；
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
//通过反射对有参私有构造赋值
public static void Demo14(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Object o = null;
try {
o = aClass.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
Person o1 = (Person) o;
Method privateMethod = null;
try {
privateMethod = aClass.getDeclaredMethod("privateMethod", String.class);
privateMethod.setAccessible(true);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
try {
privateMethod.invoke(o1,"张三");//方法的调用通过invoke()；
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
//通过反射获取指定的公共方法
public static void Demo15(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Constructor constructor = null;
try {
constructor = aClass.getConstructor(int.class);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
System.out.println(constructor);
}
//通过反射获取指定的私有构造方法
public static void Demo16(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Constructor declaredConstructor = null;
try {
declaredConstructor = aClass.getDeclaredConstructor(String.class);
declaredConstructor.setAccessible(true);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
System.out.println(declaredConstructor);
}
//通过反射获取指定的私有构造方法并实例化
public static void Demo17(){
Class aClass = null;
try {
aClass = Class.forName("refelect.Person");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Constructor declaredConstructor = null;
try {
declaredConstructor = aClass.getDeclaredConstructor(String.class);
declaredConstructor.setAccessible(true);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
Object o = null;
try {
o = declaredConstructor.newInstance("张三");
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
Person o1 = (Person) o;
System.out.println(o1.getName());
}
}