1简单Class

package com.ruoyi.app;

class User {

    private String u_name;
    private Company company;

    @Override
    public String toString() {
        return "User{" +
                "u_name='" + u_name + '\'' +
                ", company=" + company +
                '}';
    }

    public User() {
        System.out.println(Thread.currentThread().getName() + "~~~");
    }


    static class Company {

        private String c_name;


        private void setName(String name){

            c_name+=name+"setName";
        }

        @Override
        public String toString() {
            return "Company{" +
                    "c_name='" + c_name + '\'' +
                    '}';
        }
    }
}

2通过使用 setAccessible 解除对象的访问控制符

    public static void main(String[] args) throws Exception {

        Class<?> cls = Class.forName("com.ruoyi.app.User");//获取指定类的Class对象
        Object obj = cls.getDeclaredConstructor().newInstance();//实例化对象(分配成员空间)
        Field nameField = cls.getDeclaredField("u_name");// 获取成员对象
        nameField.setAccessible(true);//放开权限没有封装了
        nameField.set(obj, "卡伦人");//等价于:Person对象name="番茄强";

        Field companyField = cls.getDeclaredField("company");
        companyField.setAccessible(true);

        Class<?> companyClass = Class.forName("com.ruoyi.app.User$Company");
        Object companyObj = companyClass.getDeclaredConstructor().newInstance();


        Method companyMethod = companyClass.getDeclaredMethod("setName", String.class);
        companyMethod.setAccessible(true);
        companyMethod.invoke(companyObj, "测试公司");
        companyField.set(obj, companyObj);

        System.out.println(obj);//等价于:Person对象name

    }