net.wimpi.modbus.io.ModbusUDPTransaction Maven / Gradle / Ivy
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/***
* 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.io;
import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusException;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.ModbusSlaveException;
import net.wimpi.modbus.msg.ExceptionResponse;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.net.UDPMasterConnection;
import net.wimpi.modbus.net.UDPTerminal;
import net.wimpi.modbus.util.AtomicCounter;
import net.wimpi.modbus.util.Mutex;
/**
* Class implementing the ModbusTransaction
* interface for the UDP transport mechanism.
*
* @author Dieter Wimberger
* @version 1.2 (@date@)
*/
public class ModbusUDPTransaction
implements ModbusTransaction {
//class attributes
private static AtomicCounter c_TransactionID =
new AtomicCounter(Modbus.DEFAULT_TRANSACTION_ID);
//instance attributes and associations
private UDPTerminal m_Terminal;
private ModbusTransport m_IO;
private ModbusRequest m_Request;
private ModbusResponse m_Response;
private boolean m_ValidityCheck =
Modbus.DEFAULT_VALIDITYCHECK;
private int m_Retries = Modbus.DEFAULT_RETRIES;
private int m_RetryCounter = 0;
private Mutex m_TransactionLock = new Mutex();
/**
* Constructs a new ModbusUDPTransaction
* instance.
*/
public ModbusUDPTransaction() {
}//constructor
/**
* Constructs a new ModbusUDPTransaction
* instance with a given ModbusRequest to
* be send when the transaction is executed.
*
*
* @param request a ModbusRequest instance.
*/
public ModbusUDPTransaction(ModbusRequest request) {
setRequest(request);
}//constructor
/**
* Constructs a new ModbusUDPTransaction
* instance with a given UDPTerminal to
* be used for transactions.
*
*
* @param terminal a UDPTerminal instance.
*/
public ModbusUDPTransaction(UDPTerminal terminal) {
setTerminal(terminal);
}//constructor
/**
* Constructs a new ModbusUDPTransaction
* instance with a given ModbusUDPConnection
* to be used for transactions.
*
*
* @param con a ModbusUDPConnection instance.
*/
public ModbusUDPTransaction(UDPMasterConnection con) {
setTerminal(con.getTerminal());
}//constructor
/**
* Sets the terminal on which this ModbusTransaction
* should be executed.
*
* @param terminal a UDPSlaveTerminal.
*/
public void setTerminal(UDPTerminal terminal) {
m_Terminal = terminal;
if (terminal.isActive()) {
m_IO = terminal.getModbusTransport();
}
}//setConnection
public void setRequest(ModbusRequest req) {
m_Request = req;
//m_Response = req.getResponse();
}//setRequest
public ModbusRequest getRequest() {
return m_Request;
}//getRequest
public ModbusResponse getResponse() {
return m_Response;
}//getResponse
public int getTransactionID() {
return c_TransactionID.get();
}//getTransactionID
public void setCheckingValidity(boolean b) {
m_ValidityCheck = b;
}//setCheckingValidity
public boolean isCheckingValidity() {
return m_ValidityCheck;
}//isCheckingValidity
public int getRetries() {
return m_Retries;
}//getRetries
public void setRetries(int num) {
m_Retries = num;
}//setRetries
public void execute() throws ModbusIOException,
ModbusSlaveException,
ModbusException {
//1. assert executeability
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_Terminal.isActive()) {
try {
m_Terminal.activate();
m_IO = m_Terminal.getModbusTransport();
} catch (Exception ex) {
throw new ModbusIOException("Activation failed.");
}
}
//3. Retry transaction m_Retries times, in case of
//I/O Exception problems.
m_RetryCounter = 0;
while (m_RetryCounter <= m_Retries) {
try {
//toggle the id
m_Request.setTransactionID(c_TransactionID.increment());
//3. write request, and read response,
// while holding the lock on the IO object
synchronized (m_IO) {
//write request message
m_IO.writeMessage(m_Request);
//read response message
m_Response = m_IO.readResponse();
break;
}
} catch (ModbusIOException ex) {
m_RetryCounter++;
continue;
}
}
//4. deal with "application level" exceptions
if (m_Response instanceof ExceptionResponse) {
throw new ModbusSlaveException(
((ExceptionResponse) m_Response).getExceptionCode()
);
}
if (isCheckingValidity()) {
checkValidity();
}
} catch (InterruptedException ex) {
throw new ModbusIOException("Thread acquiring lock was interrupted.");
} finally {
m_TransactionLock.release();
}
}//execute
/**
* Asserts if this ModbusTCPTransaction is
* executable.
*
* @throws ModbusException if this transaction cannot be
* asserted as executable.
*/
private void assertExecutable()
throws ModbusException {
if (m_Request == null ||
m_Terminal == 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
}//class ModbusUDPTransaction