反射
定义：
反射允许对封装类的字段，方法和构造 函数的信息进行编程访问
图来自黑马程序员
获取class对象的三种方式：
1）Class.forName("全类名")
2）类名.class
3) 对象.getClass()
图来自黑马程序员
package com.lazyGirl.reflectdemo;public class MyReflectDemo1 {public static void main(String[] args) throws ClassNotFoundException {//最常见Class clazz = Class.forName("com.lazyGirl.reflectdemo.Student");System.out.println(clazz);Class clazz2 = Student.class;System.out.println(clazz2);System.out.println(clazz == clazz2);Student student = new Student();Class clazz3 = student.getClass();System.out.println(clazz3);System.out.println(clazz == clazz3);}
}
输出：
获取构造方法：
图来自黑马程序员
package com.lazyGirl.reflectdemo.demo1;import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Parameter;public class Demo1 {public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {Class clazz = Class.forName("com.lazyGirl.reflectdemo.demo1.Student");Constructor[] cons = clazz.getConstructors();for (Constructor c : cons) {System.out.println(c);}System.out.println();Constructor[] cons1 = clazz.getDeclaredConstructors();for (Constructor c : cons1) {System.out.println(c);}System.out.println();Constructor cons2 = clazz.getDeclaredConstructor();System.out.println(cons2);System.out.println();Constructor cons3 = clazz.getDeclaredConstructor(String.class);System.out.println(cons3);System.out.println();Constructor cons4 = clazz.getDeclaredConstructor(int.class);System.out.println(cons4);System.out.println();Constructor cons5 = clazz.getDeclaredConstructor(String.class, int.class);System.out.println(cons5);int modifiers = cons5.getModifiers();System.out.println(modifiers);System.out.println();Parameter[] parameters = cons5.getParameters();for (Parameter p : parameters) {System.out.println(p);}cons5.setAccessible(true);Student stu = (Student) cons5.newInstance("hhh",16);System.out.println(stu);}
}
输出：
获取成员变量：
图来自黑马程序员
package com.lazyGirl.reflectdemo.demo2;import java.lang.reflect.Field;public class Demo {public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {Class clazz = Class.forName("com.lazyGirl.reflectdemo.demo2.Student");Field[] fields = clazz.getFields();for (Field field : fields) {System.out.println(field.getName());}System.out.println();Field[] declaredFields = clazz.getDeclaredFields();for (Field field : declaredFields) {System.out.println(field.getName());}System.out.println();Field gender = clazz.getField("gender");System.out.println(gender);System.out.println();Field declaredName = clazz.getDeclaredField("name");System.out.println(declaredName);System.out.println();int modifiers = declaredName.getModifiers();System.out.println(modifiers);String name = declaredName.getName();System.out.println(name);System.out.println();Class<?> type = declaredName.getType();System.out.println(type);Student student = new Student("hhh",16,"女");declaredName.setAccessible(true);Object value = declaredName.get(student);System.out.println(value);declaredName.set(student,"hhhh");System.out.println(student);}
}
输出：
获取成员方法：
图来自黑马程序员
package com.lazyGirl.reflectdemo.demo3;import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;public class Demo {public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, IllegalAccessException {Class clazz = Class.forName("com.lazyGirl.reflectdemo.demo3.Student");//包含父类的方法
// Method[] methods = clazz.getMethods();//不能获取父类方法，但是可以访问私有方法Method[] methods = clazz.getDeclaredMethods();for (Method method : methods) {System.out.println(method);}Method method = clazz.getMethod("eat", String.class);System.out.println(method);int modifiers = method.getModifiers();System.out.println(modifiers);String name = method.getName();System.out.println(name);Parameter[] parameters = method.getParameters();for (Parameter parameter : parameters) {System.out.println(parameter);}Class[] exceptions = method.getExceptionTypes();for (Class exception : exceptions) {System.out.println(exception);}Student student = new Student();method.invoke(student,"cake");}
}
Student类：
package com.lazyGirl.reflectdemo.demo3;public class Student {private String name;private int age;public Student() {}public Student(String name, int age) {this.name = name;this.age = age;}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;}public void sleep(){System.out.println("sleep");}public void eat(String food) throws InterruptedException,ClassCastException{System.out.println("eat " + food);}public void eat(String food, int time){System.out.println("eat " + food + " " + time);}@Overridepublic String toString() {return "Student{" +"name='" + name + '\'' +", age=" + age +'}';}
}
输出：
作用：
获取一个类里面所有的信息，获取到了之后，再执行其他业务逻辑
结合配置文件，动态的创建对象并调用方法
package com.lazyGirl.reflectdemo.demo5;import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Properties;public class Test {public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException {Properties prop = new Properties();FileInputStream fis = new FileInputStream("pro.properties");prop.load(fis);fis.close();System.out.println(prop);String classname = (String) prop.get("classname");String methdName = (String) prop.get("method");System.out.println(classname);System.out.println(methdName);Class clazz = Class.forName(classname);Constructor constructor = clazz.getConstructor();Object o = constructor.newInstance();System.out.println(o);Method method = clazz.getDeclaredMethod(methdName);method.setAccessible(true);method.invoke(o);}
}
properties文件：
classname=com.lazyGirl.reflectdemo.demo5.Student
method=study输出：
动态代理：
无侵入式的给代码增加额外的功能
程序为什么需要代理：对象身上干的事太多，可以通过代理来转移部分职业
对象有什么方法想被代理，代理就一定要有对应的方法
java通过接口保证对象和代理
格式：
图来自黑马程序员
