ModbusRTUTCPTransaction.java

package org.openmuc.framework.driver.modbus.rtutcp.bonino;

import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusException;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.ModbusSlaveException;
import net.wimpi.modbus.io.ModbusTransaction;
import net.wimpi.modbus.io.ModbusTransport;
import net.wimpi.modbus.msg.ExceptionResponse;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.util.AtomicCounter;
import net.wimpi.modbus.util.Mutex;

/**
 * @author bonino
 * 
 *         https://github.com/dog-gateway/jamod-rtu-over-tcp
 * 
 */
public class ModbusRTUTCPTransaction implements ModbusTransaction {

    // class attributes
    private static AtomicCounter c_TransactionID = new AtomicCounter(Modbus.DEFAULT_TRANSACTION_ID);

    // instance attributes and associations
    private RTUTCPMasterConnection m_Connection;
    private ModbusTransport m_IO;
    private ModbusRequest m_Request;
    private ModbusResponse m_Response;
    private boolean m_ValidityCheck = Modbus.DEFAULT_VALIDITYCHECK;
    private boolean m_Reconnecting = Modbus.DEFAULT_RECONNECTING;
    private int m_Retries = Modbus.DEFAULT_RETRIES;

    private final Mutex m_TransactionLock = new Mutex();

    /**
     * 
     */
    public ModbusRTUTCPTransaction() {
        // TODO Auto-generated constructor stub
    }

    /**
     * Constructs a new <tt>ModbusTCPTransaction</tt> instance with a given <tt>ModbusRequest</tt> to be send when the
     * transaction is executed.
     * 
     * @param request
     *            a <tt>ModbusRequest</tt> instance.
     */
    public ModbusRTUTCPTransaction(ModbusRequest request) {
        setRequest(request);
    }// constructor

    /**
     * Constructs a new <tt>ModbusTCPTransaction</tt> instance with a given <tt>TCPMasterConnection</tt> to be used for
     * transactions.
     * 
     * @param con
     *            a <tt>TCPMasterConnection</tt> instance.
     */
    public ModbusRTUTCPTransaction(RTUTCPMasterConnection con) {
        setConnection(con);
    }// constructor

    /**
     * Sets the connection on which this <tt>ModbusTransaction</tt> should be executed.
     * <p>
     * An implementation should be able to handle open and closed connections. <br>
     * 
     * @param con
     *            a <tt>TCPMasterConnection</tt>.
     */
    public void setConnection(RTUTCPMasterConnection con) {
        m_Connection = con;
        m_IO = con.getModbusTransport();
    }// setConnection

    @Override
    public void setRequest(ModbusRequest req) {
        m_Request = req;
    }// setRequest

    @Override
    public ModbusRequest getRequest() {
        return m_Request;
    }// getRequest

    @Override
    public ModbusResponse getResponse() {
        return m_Response;
    }// getResponse

    @Override
    public int getTransactionID() {
        return c_TransactionID.get();
    }// getTransactionID

    @Override
    public void setCheckingValidity(boolean b) {
        m_ValidityCheck = b;
    }// setCheckingValidity

    @Override
    public boolean isCheckingValidity() {
        return m_ValidityCheck;
    }// isCheckingValidity

    /**
     * Sets the flag that controls whether a connection is openend and closed for <b>each</b> execution or not.
     * 
     * @param b
     *            true if reconnecting, false otherwise.
     */
    public void setReconnecting(boolean b) {
        m_Reconnecting = b;
    }// setReconnecting

    /**
     * Tests if the connection will be openend and closed for <b>each</b> execution.
     * 
     * @return true if reconnecting, false otherwise.
     */
    public boolean isReconnecting() {
        return m_Reconnecting;
    }// isReconnecting

    @Override
    public int getRetries() {
        return m_Retries;
    }// getRetries

    @Override
    public void setRetries(int num) {
        m_Retries = num;
    }// setRetries

    @Override
    public void execute() throws ModbusIOException, ModbusSlaveException, ModbusException {

        // 1. check that the transaction can be executed
        assertExecutable();

        try {
            // 2. Lock transaction
            /**
             * Note: The way this explicit synchronization is implemented at the moment, there is no ordering of pending
             * threads. The Mutex will simply call notify() and the JVM will handle the rest.
             */
            m_TransactionLock.acquire();

            // 3. open the connection if not connected
            if (!m_Connection.isConnected()) {
                try {
                    m_Connection.connect();
                    m_IO = m_Connection.getModbusTransport();
                } catch (Exception ex) {
                    throw new ModbusIOException("Connecting failed.");
                }
            }

            // 4. Retry transaction m_Retries times, in case of
            // I/O Exception problems.
            int retryCounter = 0;

            while (retryCounter < m_Retries) {
                try {
                    // toggle and set the id
                    m_Request.setTransactionID(c_TransactionID.increment());

                    // 3. write request, and read response
                    m_IO.writeMessage(m_Request);

                    // read response message
                    m_Response = m_IO.readResponse();
                    break;
                } catch (ModbusIOException ex) {
                    if (retryCounter == m_Retries) {
                        throw new ModbusIOException("Executing transaction failed (tried " + m_Retries + " times)");
                    }
                    else {
                        retryCounter++;
                        continue;
                    }
                }
            }

            // 5. deal with "application level" exceptions
            if (m_Response instanceof ExceptionResponse) {
                throw new ModbusSlaveException(((ExceptionResponse) m_Response).getExceptionCode());
            }

            // 6. close connection if reconnecting
            if (isReconnecting()) {
                m_Connection.close();
            }

            // 7. Check transaction validity
            if (isCheckingValidity()) {
                checkValidity();
            }

        } catch (InterruptedException ex) {
            throw new ModbusIOException("Thread acquiring lock was interrupted.");
        } finally {
            m_TransactionLock.release();
        }
    }// execute

    /**
     * Asserts if this <tt>ModbusTCPTransaction</tt> is executable.
     * 
     * @throws ModbusException
     *             if the transaction cannot be asserted as executable.
     */
    private void assertExecutable() throws ModbusException {
        if (m_Request == null || m_Connection == null) {
            throw new ModbusException("Assertion failed, transaction not executable");
        }
    }// assertExecuteable

    /**
     * Checks the validity of the transaction, by checking if the values of the response correspond to the values of the
     * request. Use an override to provide some checks, this method will only return.
     * 
     * @throws ModbusException
     *             if this transaction has not been valid.
     */
    protected void checkValidity() throws ModbusException {
    }// checkValidity

}