Chapter 29 - Create Your Point Discovery Request

NOTE: This class is similar to your driver's read request, write request, ping request, and device discovery request classes. Please follow either A or B but not both:

If your driver's protocol features a message that can be sent to the field-device to ask it for a list data points:

Create a class named BYourDriverPointDiscoverRequest that extends BDdfDiscoveryRequest in the package com.yourCompany.yourDriver.comm.req

To do this, create a text file named BYourDriverPointDiscoverRequest.java in the jarFileName/src/com/yourCompany/yourDriver/comm/req folder. Inside the text file, start with the following text:

package com.yourCompany.yourDriver.comm.req;

import javax.baja.sys.*;

import com.tridium.ddf.identify.*;
import com.tridium.ddf.comm.*;
import com.tridium.ddf.comm.req.*;
import com.tridium.ddf.comm.rsp.*;

import com.yourCompany.yourDriver.identify.*;

public class BYourDriverPointDiscoverRequest
  extends BDdfDiscoveryRequest
{
  /*-
  class BYourDriverPointDiscoverRequest
  {
  }
  -*/
}

Define the toByteArray method.

In the toByteArray method, call getDiscoverParameters() and cast the result to BYourDriverPointDiscoverParams. Most of the information that you need will be available in this instance of your driver's BYourDriverPointDiscoverParams class. You created this class previously during today's lesson.

package com.yourCompany.yourDriver.comm.req;

import javax.baja.sys.*;

import com.tridium.ddf.identify.*;
import com.tridium.ddf.comm.*;
import com.tridium.ddf.comm.req.*;
import com.tridium.ddf.comm.rsp.*;

import com.yourCompany.yourDriver.identify.*;
import com.yourCompany.yourDriver.comm.rsp.*;


public class BYourDriverPointDiscoverRequest
  extends BDdfDiscoveryRequest
{
  /*-
  class BYourDriverPointDiscoverRequest
  {
  }
  -*/

  public byte[] toByteArray()
  {
    BYourDriverPointDiscoverParams ptDscvParams =
      (BYourDriverPointDiscoverParams)getDiscoverParameters();

    return new byte[]{
      //...
      // Substitute value1 and value2 with your own properties
      // As necessary to construct the outgoing frame that your
      // Driver's protocol defines for requesting all points or
      // A series (group) of points from a field-device.
      (byte)ptDscvParams.getValue1(),
      (byte)ptDscvParams.getValue2(),
      //...
    };
  }
}

HINT: If you require information about the field-device in order to construct the byte array that the toByteArray method returns then simply call the getDeviceId method and cast the result to BYourDriverDeviceId!
In fact, all requests have access to the device id in this fashion.

If your driver's protocol does not feature a message that can be sent to the field-device to ask it for a list of data points then you should modify your driver's read request to also serve as the point discover request.

Modify the declaration of BYourDriverReadRequest and make it implement BIDdfDiscoverRequest. Also make it import the following additional packages:

...

import com.tridium.ddf.discover.*;
import com.tridium.ddf.identify.*;

...

public class BYourDriverReadRequest
  extends BDdfReadRequest
  implements BIDdfDiscoverRequest
{
 ...
}

Add the following property to the slotomatic statement of BYourDriverReadRequest

  /*-
  class BYourDriverReadRequest
  {
    properties
    {
      ...
      discoverParameters : BDdfIdParams
         -- This provides the necessary data that the toByteArray method
         -- Needs in order to construct the byte array. Since this class
         -- Is the read request and also serves as the discovery request,
         -- Then this property's value will be a copy of the value of the
         -- Read Parameters property.
        default{[new BYourDriverReadParams()]}
      ...
    }

  }
  -*/

Add the following methods to BYourDriverReadRequest. Please add them exactly as-is. You shouldn't need to modify these methods, except maybe to change the comments.

  /**
   * The setDiscoverer method will be passed an instance of
   * IDdfDiscoverer. You need to retain the reference on
   * the instance and return it (whenever requested) from
   * the getDiscoverer method.
   */
  IDdfDiscoverer discoverer = null;
  /**
   * The BDdfAutoDiscoveryJob will pass an inner instance
   * of itself to the setDiscoverer method. In there, you
   * need to save away the reference. In here, please return
   * the most recent reference that was passed to the
   * setDiscoverer method.
   */
  public IDdfDiscoverer getDiscoverer(){return discoverer;}
  /**
   * The BDdfAutoDiscoveryJob will pass an inner instance
   * of itself here. Please save away the reference. Other
   * than that, you should not need to concern yourself
   * with this.
   */
  public void setDiscoverer(IDdfDiscoverer discoverer)
  {
    this.discoverer=discoverer;
  }

NOTES:

You already defined the toByteArray method during one of the previous day's lessons. You should not need to change it any further. It pulls the data necessary to construct the outgoing frame from the read parameters structure.
The discover parameters structure will be assigned a copy of the read parameters structure. This is a special case since you are using the read request also as a discovery request.