Java反射用法简单示例

野性酷女 2022-03-19 16:46 259阅读 0赞

话不多说了，直接上码，备注里都比较详细：

package com.example.demoprovider;
    
    import java.lang.reflect.Constructor;
    import java.lang.reflect.Field;
    import java.lang.reflect.Method;
    
    public class ReflecDemo {
    
        public static void main(String[] args)  {
            //一、获取class对象，三种方法
            //(1)通过类直接获取
            Class clazz1 = Student.class;
            //（2）new对象获取
            Student stu = new Student();
            Class clazz2 =  stu.getClass();
            //(3)通过类全路径获取（真正的反射机制）
            Class clazz3 = null;
            try {
                clazz3 = Class.forName("com.example.demoprovider.Student");
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
            //二、获取类对，两种方法
            //（1）直接通过class对象获取（默认使用无参构造，如果没有构造则抛异常）
            Student student1;
            try {
                student1 = (Student) clazz3.newInstance();
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            //(2)通过构造函数获取类对象（获取构造函数的接口有好几个，在此不一一演示）
            Constructor constructor;
            Student student2 = null;
            try {
                constructor = clazz3.getConstructor(String.class,String.class,String.class);
                student2 = (Student) constructor.newInstance("小明","20","女");
                System.out.println("student2="+ student2.getName()+";"+student2.getAge()+";"+student2.getGender());
            } catch (Exception e) {
                e.printStackTrace();
            }
            //三、获取类对象的变量（获取变量的接口也有几个，在此不一一演示）
            Field field = null;
            try {
                field = clazz3.getDeclaredField("name");
                //解除私有限定,设置私有变量可访问
                field.setAccessible(true);
                field.set(student2,"小红");
                System.out.println(student2.getName());
            } catch (Exception e) {
                e.printStackTrace();
            }
            //四、执行方法（获取方法的接口也有好几个，在此不一一演示）
            Method method;
            try {
                method = clazz3.getDeclaredMethod("showStudentInfo");
                method.invoke(student2);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    
    class Student {
        private String name;
        private String age;
        private String gender;
    
        public Student() {
        }
    
        public Student(String name, String age, String gender) {
            this.name = name;
            this.age = age;
            this.gender = gender;
        }
    
        public void showStudentInfo(){
            System.out.println("反射执行：name="+name+";age="+age+";gender="+gender);
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getAge() {
            return age;
        }
    
        public void setAge(String age) {
            this.age = age;
        }
    
        public String getGender() {
            return gender;
        }
    
        public void setGender(String gender) {
            this.gender = gender;
        }
    }