Java反射

package lucas;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Properties;

public class MainCla {
    public static void main(String[] args) throws IllegalAccessException, InvocationTargetException, InstantiationException {
        //第一种方式获取class对象，已经new出来了，还整个屁
        Student stu = new Student();//new后产生两个对象，一个Student对象，一个Class对象
        Class<? extends Student> stuC = stu.getClass();//获取class对象
        System.out.println(stuC.getName()); //lucas.Student

        //第二种方式获取class对象，需要导包
        Class<Student> stuC2 = Student.class;
        System.out.println(stuC == stuC2);

        //第三种方式获取Class对象,Class类的静态方法
        try {
            Class<?> stuC3 = Class.forName("lucas.Student");////注意此字符串必须是真实路径，就是带包名的类路径，包名.类名
            System.out.println(stuC == stuC3);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

        Constructor<?>[] conArray = stuC2.getConstructors();
        for(Constructor c : conArray) {
            System.out.println(c);
        }

        System.out.println("---------------------------------------------declared------------------------------------------");

        Constructor<?>[] declaredCon = stuC2.getDeclaredConstructors();
        for (Constructor c : declaredCon)
        {
            System.out.println(c);
        }

        System.out.println("---------------------------------------------获取无惨、共有------------------------------------------");
        try {
            Constructor<? extends Student> cons = stuC.getConstructor(null);
            System.out.println(cons);

            //调用构造方法
            Student student = cons.newInstance();

        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        System.out.println("---------------------------------------------私有、有参的------------------------------------------");
        try {
            Constructor<? extends Student> declaredConstructor = stuC.getDeclaredConstructor(char.class);
            System.out.println(declaredConstructor);

            //暴力访问
            declaredConstructor.setAccessible(true);
            Student student = declaredConstructor.newInstance('男');

            Constructor<? extends Student> dc = stuC.getDeclaredConstructor(int.class);
            dc.setAccessible(true);
            Student st = dc.newInstance(20);



        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }


        System.out.println("---------------------------------------------公共字段------------------------------------------");
        Field[] fields = stuC.getFields();
        for (Field f :
                fields) {
            System.out.println(f);
        }

        System.out.println("---------------------------------------------所有字段------------------------------------------");
        Field[] fs = stuC.getDeclaredFields();
        for (Field f :
                fs) {
            System.out.println(f);
        }

        System.out.println("---------------------------------------------私有name字段，并使用（赋值）------------------------------------------");
        try {
            Field name = stuC.getDeclaredField("name");
            System.out.println(name);

            name.setAccessible(true);
            Student student = stuC.newInstance();
            name.set(student, "lucas");
            System.out.println(student.getName());

        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }

        System.out.println("---------------------------------------------所有公共的方法------------------------------------------");
        Method[] methods = stuC.getMethods();
        for (Method m :
                methods) {
            System.out.println(m);
        }

        System.out.println("---------------------------------------------所有的方法------------------------------------------");

        Method[] declaredMethods = stuC.getDeclaredMethods();
        for (Method m :
                declaredMethods) {
            System.out.println(m);
        }

        System.out.println("---------------------------------------------setName(),并唤醒------------------------------------------");
        try {
            Method setName = stuC.getMethod("setName", String.class);
            Student student = stuC.newInstance();
            setName.invoke(student,"lucas");
            System.out.println(student.getName());
        } catch (NoSuchMethodException e) {


        }


        System.out.println("---------------------------------------------Student类的main（）------------------------------------------");
        try {
            Class<?> aClass = Class.forName("lucas.Student");
            Method mainM = aClass.getMethod("main", String[].class);
            Object o = aClass.newInstance();
            mainM.invoke(o, (Object)new String[]{"a","b","c"});
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }

        System.out.println("---------------------------------------------读配置文件------------------------------------------");
        try {
            Method methodName = stuC.getMethod(getValue("methodName"));
            int info = (int)methodName.invoke(stuC.getConstructor().newInstance());
            System.out.println("..........info:" + info);

        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        System.out.println("---------------------------------------------通过反射越过泛型检查------------------------------------------");
        ArrayList<String> al = new ArrayList<String>();
        al.add("lucas");
        al.add("hello" );

        Class<? extends ArrayList> aClass = al.getClass();
        try {
            Method add = aClass.getMethod("add", Object.class);
            add.invoke( al,100);

            for (Object obj :
                    al) {
                System.out.println(obj);
            }
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }

    }

    public static String getValue(String key) throws IOException {
        Properties properties = new Properties();
        FileReader in = new FileReader("c:/users/S/desktop/pro.txt");
        properties.load(in);
        in.close();
        return properties.getProperty(key);
    }
}