Java反射的使用

灰太狼 2022-07-16 08:28 128阅读 0赞

主类：

import java.lang.reflect.Constructor;
    import java.lang.reflect.Field;
    import java.lang.reflect.Method;
    
    /**
     * Created by cuboo on 2016/10/11.
     */
    public class Main01 {
        public static void main(String agrs[]){
            Main01 mains = new Main01();
            exam01 exam = new exam01();
            //获得exam01的对象 方法1  方法2 examC = Class.forName(类路径) 方法3 examC = exam01.class
            Class examC = exam.getClass();
    //        mains.constructor(examC);
    //        mains.field(examC,exam);
            mains.method(examC,exam);
        }
        private void constructor(Class examC){
            //获得所有构造器方法
            Constructor[] constructors= examC.getDeclaredConstructors();
            //遍历构造方法
            for (int i = 0; i < constructors.length ; i++) {
                Constructor constrctor = constructors[i];
                System.out.println("是否带有可变数量的参数："+constrctor.isVarArgs());
                System.out.println("入口参数类型依次是：");
                Class[] parameter = constrctor.getParameterTypes();
                for (int j = 0; j < parameter.length; j++) {
                    System.out.println(" "+parameter[j]);
                }
                System.out.println("可能抛出的异常值：");
                Class[] exception = constrctor.getExceptionTypes();
                for (int j = 0; j < exception.length; j++) {
                    System.out.println(" "+exception[j]);
                }
    
                exam01 exam0 = null;
                while (exam0 == null){
                    //如果为privatex对象则抛出异常
                    try {
                        if (i == 2){
                            exam0 = (exam01) constrctor.newInstance();
                        }else if (i == 1){
                            exam0 = (exam01) constrctor.newInstance("2个参数的构造方法",2);
                        }else {
                            Object[] parameters = new Object[]{new String[]{"1","2","3"}};
                            exam0 = (exam01) constrctor.newInstance(parameters);
                        }
    
                    }catch (Exception e){
                        System.out.println("创建对象时抛出异常，下面执行setAccessible()方法");
                        //设置允许访问
                        constrctor.setAccessible(true);
                    }
    
                }
                exam0.print();
            }
        }
        private void field(Class examC,exam01 exam){
            //获得所有成员变量
            Field[] fields = examC.getDeclaredFields();
            for (int i = 0; i < fields.length; i++) {
                Field field = fields[i];
                //获得成员变量名称
                System.out.println("名称："+field.getName());
                System.out.println("类型："+field.getType());
                boolean isTurn = true;
                while(isTurn){
                    //如果为private则抛出异常
                    try{
                        isTurn = false;
                        System.out.println("修改前的值："+field.get(exam));
                        if (field.getType().equals(int.class)){
                           field.setInt(exam,100);
                        }else if (field.getType().equals(float.class)){
                            field.setFloat(exam,99.99f);
                        }else {
                            //设置各种类型的成员变量的值
                            field.set(exam,"成员变量"+field.getName());
                        }
                        System.out.println("修改后的值："+field.get(exam));
                    }catch (Exception e){
                        System.out.println("设置成员变量是出现异常，执行setAccessible方法");
                        field.setAccessible(true);
                        isTurn = true;
                    }
                }
            }
        }
        private  void method(Class examC,exam01 exam){
            //获得所有方法
            Method[] methods = examC.getDeclaredMethods();
            for (int i = 0; i < methods.length; i++) {
                Method method = methods[i];
                System.out.println("\n方法名称："+method.getName());
                System.out.println("是否可变参数："+method.isVarArgs());
                System.out.println("入口参数依次为：");
                Class[] parameters = method.getParameterTypes();
                if (parameters.length == 0){
                    System.out.println("null");
                }
                for (int j = 0; j < parameters.length; j++) {
                    System.out.println(parameters[j]);
                }
                //获得方法返回值的类型
                System.out.println("返回值类型："+method.getReturnType());
    
                boolean isTurn = true;
                while(isTurn){
                    //如果为private则抛出异常
                    try{
                        isTurn = false;
    
                        if ("staticMethod".equals(method.getName())){
                            System.out.println(method.invoke(exam));
                        }else if ("privateMethod".equals(method.getName())){
                            System.out.println(method.invoke(exam,100));
                        }else if ("protectedMethod".equals(method.getName())){
                            System.out.println(method.invoke(exam,"string",100));
                        }else if ("publicMethod".equals(method.getName())){
                            Object[] paras = new Object[]{new String[]{"a","b","c"}};
                           System.out.println(method.invoke(exam,paras));
                        }
    
                    }catch (Exception e){
                        System.out.println("设置成员方法是出现异常，执行setAccessible方法");
                        method.setAccessible(true);
                        isTurn = true;
                    }
                }
            }
        }
    }
     
     调用类： /**
     * Created by cuboo on 2016/10/10.
     */
    public class exam01 {
        String s;
        int i,i2,i3;
        private String str;
        protected int num;
        public float nums;
        private exam01(){
    
        }
        protected exam01(String s,int i){
            this.s = s;
            this.i = i;
        }
        public exam01(String... strings) throws NumberFormatException{
            if (strings.length > 0){
                i = Integer.valueOf(strings[0]);
            }
            if (strings.length > 1){
                i2 = Integer.valueOf(strings[1]);
            }
            if (strings.length > 2){
                i3 = Integer.valueOf(strings[2]);
            }
        }
        public void print(){
            System.out.println("s="+s);
            System.out.println("i="+i);
            System.out.println("i2="+i2);
            System.out.println("i3="+i3);
        }
        static void staticMethod(){
            System.out.println("执行staticMethod方法");
        }
        private void privateMethod(int i){
            System.out.println("执行privateMethod方法"+i);
        }
        protected void protectedMethod(String s,int i){
            System.out.println("执行protectedMethod方法"+s+" "+i);
        }
        public String publicMethod(String... strings){
            System.out.println("执行publicMethod方法");
            for (int j = 0; j < strings.length; j++) {
                System.out.print(strings[j]+" ");
            }
            System.out.println();
            return null;
        }
    
    }