Why my hardware interface can't get command from controller?

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Hello, everyone

I have succeed to connect the Gazebo with MOVEIT by editing my yaml files and launch files. And now I decide to write a hardware interface to control my real robot by joint-trajectory-controller. When I plan&execute in MOVEIT and got the output

[ INFO] [1591108238.930099466, 183.801000000]: Controller mybot/my_trajectory_controller successfully finished  
[ INFO] [1591108239.029073528, 183.900000000]: Completed trajectory execution with status SUCCEEDED ... 
[ INFO] [1591108239.029210111, 183.900000000]: Execution completed: SUCCEEDED

But the data of the topic I publish in the "write" method does not have any change. And I run the rqt_graph. It seems that my hardware interface does not connect with the follow_joint_trajectory/action_topics . Did I write the hardware interface in a worry way?Or did I misunderstand something?

I have "connect and register the joint state interface & joint position interface"

   hardware_interface::JointStateHandle state_handle_0("joint0", &pos[0], &vel[0], &eff[0]);
   jnt_state_interface.registerHandle(state_handle_0);

   //.............

   hardware_interface::JointStateHandle state_handle_4("joint4", &pos[4], &vel[4], &eff[4]);
   jnt_state_interface.registerHandle(state_handle_4);

   registerInterface(&jnt_state_interface);

   hardware_interface::JointHandle pos_handle_0(jnt_state_interface.getHandle("joint0"), &cmd[0]);
   jnt_pos_interface.registerHandle(pos_handle_0);

   //........

   hardware_interface::JointHandle pos_handle_4(jnt_state_interface.getHandle("joint4"), &cmd[4]);
   jnt_pos_interface.registerHandle(pos_handle_4);

   registerInterface(&jnt_pos_interface);

and write(without read)

void MyHWInterface::write()
{
   for(int i=0; i<4; i++)
    {
        //ROS_INFO("[%f]", cmd[i]);
        cmd_msg[i].data=cmd[i];
            pub_cmd[i].publish(cmd_msg[i]);
    }
}

the main loop

int main(int argc, char** argv)
{
    ros::init(argc, argv, "mybot");
    ros::NodeHandle nh; 

    MyHWInterface bot;
    controller_manager::ControllerManager ctrl(&bot, nh);   //class of controller，link to bot

    ros::Rate rate(1.0 / bot.getPeriod().toSec());
    ros::AsyncSpinner spinner(1);
    spinner.start();

    ROS_INFO("HW has been launch!");

    while(ros::ok())
    {
        ctrl.update(bot.getTime(), bot.getPeriod());
        bot.write();    
        rate.sleep();
    }
    spinner.stop();

    return 0;

}

my yaml file

mybot:
  my_trajectory_controller:
    type: "position_controllers/JointTrajectoryController"
    joints:
      - joint0
      - joint1
      - joint2
      - joint3
      - joint4

  constraints:
      goal_time: &goal_time_constraint 10
      stopped_velocity_tolerance: 0
      joint0:
        goal: &goal_pos_constraint 0.5
        trajectory: &trajectory_pos_constraint 0.1
      joint1:
        goal: *goal_pos_constraint
        trajectory: *trajectory_pos_constraint
      joint2:
        goal: *goal_pos_constraint
        trajectory: *trajectory_pos_constraint
      joint3:
        goal: *goal_pos_constraint
        trajectory: *trajectory_pos_constraint
      joint4:
        goal: *goal_pos_constraint
        trajectory: *trajectory_pos_constraint


#gazebo_ros_control/pid_
  gains:
      joint0:   {p: 0.6, i: 0.1, d: 0.16, i_clamp: 1}
      joint1:   {p: 0.6, i: 0.2, d: 0.1, i_clamp: 1}
      joint2:   {p: 0.6, i: 0.1, d: 0.05, i_clamp: 1}
      joint3:   {p: 0.45, i: 0.015, d: 0.01, i_clamp: 1}
      joint4:   {p: 0.3, i: 0.01, d: 0.01, i_clamp: 1}

my direct launch file

<launch>
   <!--robot description-->
   <param name="robot_description" command="$(find xacro)/xacro --inorder '$(find mybot_description)/urdf/moveit_gazebo/mybot.xacro'" />

   <!-- my hardwareinterface -->
   <node name="mybot" pkg="mybot_control" type="myhw" output="screen"/>

   <!-- Load joint controller configurations from YAML file to parameter server -->
   <rosparam file="$(find mybot_control)/config/trajectory.yaml" command="load"/>

    <!-- load the controllers -->
    <node name="trajectory_controller_spawner" pkg="controller_manager" type="spawner" respawn="false"
    output="screen" ns="/mybot" args="my_trajectory_controller"/>


   <!--about joint states-->
    <!--<node name="joint_controller_spawner" pkg="controller_manager" type="spawner" respawn="false"
          output="screen" args="joint_state_controller" /> -->

</launch>

What should I do to ... (more)