ModbusRequest.java

/***
 * Copyright 2002-2010 jamod development team
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ***/

package net.wimpi.modbus.msg;

import net.wimpi.modbus.Modbus;

/**
 * Abstract class implementing a <tt>ModbusRequest</tt>.
 * This class provides specialised implementations with
 * the functionality they have in common.
 *
 * @author Dieter Wimberger
 * @version @version@ (@date@)
 */
public abstract class ModbusRequest extends ModbusMessageImpl {

    /**
     * Returns the <tt>ModbusResponse</tt> that
     * correlates with this <tt>ModbusRequest</tt>.
     * <p>
     *
     * @return the corresponding <tt>ModbusResponse</tt>.
     *
     *         public abstract ModbusResponse getResponse();
     */

    /**
     * Returns the <tt>ModbusResponse</tt> that
     * represents the answer to this <tt>ModbusRequest</tt>.
     * <p>
     * The implementation should take care about assembling
     * the reply to this <tt>ModbusRequest</tt>.
     * <p>
     *
     * @return the corresponding <tt>ModbusResponse</tt>.
     */
    public abstract ModbusResponse createResponse();

    /**
     * Factory method for creating exception responses with the
     * given exception code.
     *
     * @param EXCEPTION_CODE the code of the exception.
     * @return a ModbusResponse instance representing the exception
     *         response.
     */
    public ModbusResponse createExceptionResponse(int EXCEPTION_CODE) {
        ExceptionResponse response = new ExceptionResponse(this.getFunctionCode(), EXCEPTION_CODE);
        if (!isHeadless()) {
            response.setTransactionID(this.getTransactionID());
            response.setProtocolID(this.getProtocolID());
            response.setUnitID(this.getUnitID());
        } else {
            response.setHeadless();
        }
        return response;
    }// createExceptionResponse

    /**
     * Factory method creating the required specialized <tt>ModbusRequest</tt>
     * instance.
     *
     * @param functionCode the function code of the request as <tt>int</tt>.
     * @return a ModbusRequest instance specific for the given function type.
     */
    public static ModbusRequest createModbusRequest(int functionCode) {
        ModbusRequest request = null;

        switch (functionCode) {
            case Modbus.READ_MULTIPLE_REGISTERS:
                request = new ReadMultipleRegistersRequest();
                break;
            case Modbus.READ_INPUT_DISCRETES:
                request = new ReadInputDiscretesRequest();
                break;
            case Modbus.READ_INPUT_REGISTERS:
                request = new ReadInputRegistersRequest();
                break;
            case Modbus.READ_COILS:
                request = new ReadCoilsRequest();
                break;
            case Modbus.WRITE_MULTIPLE_REGISTERS:
                request = new WriteMultipleRegistersRequest();
                break;
            case Modbus.WRITE_SINGLE_REGISTER:
                request = new WriteSingleRegisterRequest();
                break;
            case Modbus.WRITE_COIL:
                request = new WriteCoilRequest();
                break;
            case Modbus.WRITE_MULTIPLE_COILS:
                request = new WriteMultipleCoilsRequest();
                break;
            default:
                request = new IllegalFunctionRequest(functionCode);
                break;
        }
        return request;
    }// createModbusRequest

}// class ModbusRequest