ProcessVariable (Java Channel Access 2.4.4-j8 API)

java.lang.Object
- gov.aps.jca.cas.ProcessVariable

Direct Known Subclasses:

EnumProcessVariable, MemoryProcessVariable, NumericProcessVariable, StringProcessVariable
```
public abstract class ProcessVariable
extends Object
```
Process variable (PV).

Version:

$Id: ProcessVariable.java,v 1.12 2007-12-04 12:57:40 msekoranja Exp $

Author:

Matej Sekoranja

Field Summary

Fields
Modifier and Type	Field and Description
`protected Severity`	`ackS` Alarm Acknowledge Severity.
`protected boolean`	`ackT` Alarm Acknowledge Transient.
`protected int`	`channelCount` Channel count (number of clients).
`protected ProcessVariableEventCallback`	`eventCallback` Process variable event callback.
`protected boolean`	`interest` Interess flag.
`protected String`	`name` Process variable name.

Constructor Summary

Constructors
Constructor and Description

ProcessVariable(String name, ProcessVariableEventCallback eventCallback)
Create process variable with given name.

Constructors
Constructor and Description
`ProcessVariable(String name, ProcessVariableEventCallback eventCallback)` Create process variable with given name.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`ServerChannel`	`createChannel(int cid, int sid, String userName, String hostName)` This method is called each time that a PV is attached to by a client.
`void`	`destroy()` Destory process variable.
`Severity`	`getAckS()` Get acknowledged alarm severity.
`int`	`getDimensionSize(int dimension)` The method `getDimensionSize(dimension)` returns the maximum number of elements in a particular dimension of the hypercube as follows:
`String[]`	`getEnumLabels()` Get enum string labels.
`ProcessVariableEventCallback`	`getEventCallback()` Get event callback.
`int`	`getMaxDimension()` Returns the maximum bounding box for all present and future data stored within the PV.
`String`	`getName()` Get process variable name.
`abstract DBRType`	`getType()` The best type for clients to use when accessing the value of the PV.
`void`	`interestDelete()` Called by the server library each time that it wishes to remove its subscription for PV value change events from the server tool via `ProcessVariableEventCallback.postEvent()` method.
`void`	`interestRegister()` Called by the server libary each time that it wishes to subscribe for PV change notification from the server tool via `ProcessVariableEventCallback.postEvent()` method.
`boolean`	`isAckT()` Get acknowledged alarm transient flag.
`void`	`printInfo()` Prints detailed information about the Context to the standard output stream.
`void`	`printInfo(PrintStream out)` Prints detailed information about the Context to the specified output stream.
`abstract CAStatus`	`read(DBR value, ProcessVariableReadCallback asyncReadCallback)` Read process variable value.
`void`	`registerChannel(ServerChannel channel)` Register channel to this process variable.
`void`	`setAckS(Severity ackS)` Set acknowledged alarm severity.
`void`	`setAckT(boolean ackT)` Set acknowledged alarm transient flag.
`void`	`setEventCallback(ProcessVariableEventCallback eventCallback)` Set event callback.
`void`	`unregisterChannel(ServerChannel channel)` Unregister channel from this process variable.
`abstract CAStatus`	`write(DBR value, ProcessVariableWriteCallback asyncWriteCallback)` Write process variable value.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - name
```
protected String name
```
    Process variable name.
  - eventCallback
```
protected ProcessVariableEventCallback eventCallback
```
    Process variable event callback.
  - interest
```
protected volatile boolean interest
```
    Interess flag.
    
    See Also:
    
    interestRegister()
  - channelCount
```
protected int channelCount
```
    Channel count (number of clients).
  - ackS
```
protected volatile Severity ackS
```
    Alarm Acknowledge Severity.
  - ackT
```
protected volatile boolean ackT
```
    Alarm Acknowledge Transient.
- Constructor Detail
  - ProcessVariable
```
public ProcessVariable(String name,
                       ProcessVariableEventCallback eventCallback)
```
    Create process variable with given name.
    
    Parameters:
    
    name - process variable name.
    
    eventCallback - event callback, can be null.
- Method Detail
  - getName
```
public String getName()
```
    Get process variable name. If there are several aliases for the same PV this routine should return the canonical (base) name for the PV.
    
    Returns:
    
    process variable name.
  - getType
```
public abstract DBRType getType()
```
    The best type for clients to use when accessing the value of the PV. Only basic types e.g. BYTE, INTEGER and not STS_BYTE have to be returned.
    
    Returns:
    
    best type for clients.
  - getMaxDimension
```
public int getMaxDimension()
```
    Returns the maximum bounding box for all present and future data stored within the PV. The method getDimensionCount() returns the maximum number of dimensions in the hypercube (0=scalar, 1=array, 2=plane, 3=cube ...). The default (base) "getDimensionCount()" returns zero (scalar). Clients will see that the PV's data is scalar if these routines are not supplied in the derived class. If the "dimension" argument to getDimensionSize() is set to zero then the bound on the first dimension is being fetched. If the "dimension" argument to getDimensionSize() is set to one then the bound on the second dimension are being fetched...
    
    Returns:
    
    number of dimensions presenting the data.
  - getDimensionSize
```
public int getDimensionSize(int dimension)
```
    The method getDimensionSize(dimension) returns the maximum number of elements in a particular dimension of the hypercube as follows:
```
   scalar - getDimensionCount() returns 0
   
   array -  getDimensionCount() returns 1
            getDimensionSize(0) supplies number of elements in array
            
   plane -  getDimensionCount() returns 2
            getDimensionSize(0) supplies number of elements in X dimension
            getDimensionSize(1) supplies number of elements in Y dimension
           
   cube -   getDimensionCount() returns 3
            getDimensionSize(0) supplies number of elements in X dimension
            getDimensionSize(1) supplies number of elements in Y dimension
            getDimensionSize(2) supplies number of elements in Z dimension
            
   ...
 
```
    The default (base) "getDimensionSize()" returns one (scalar bounds) for all dimensions.
    Parameters:
    
    dimension - dimension for which to fecth its size.
    
    Returns:
    
    requested dimenstion size.
  - getEnumLabels
```
public String[] getEnumLabels()
```
    Get enum string labels. If process variable is type of ENUM it should override this method and return labels.
    
    Returns:
    
    enum string labels.
  - getAckS
```
public Severity getAckS()
```
    Get acknowledged alarm severity.
    
    Returns:
    
    acknowledged alarm severity.
  - setAckS
```
public void setAckS(Severity ackS)
```
    Set acknowledged alarm severity.
    
    Parameters:
    
    ackS - acknowledged alarm severity to set.
  - isAckT
```
public boolean isAckT()
```
    Get acknowledged alarm transient flag.
    
    Returns:
    
    acknowledged alarm transient flag
  - setAckT
```
public void setAckT(boolean ackT)
```
    Set acknowledged alarm transient flag.
    
    Parameters:
    
    ackT - acknowledged alarm transient flag to set
  - interestRegister
```
public void interestRegister()
```
    Called by the server libary each time that it wishes to subscribe for PV change notification from the server tool via ProcessVariableEventCallback.postEvent() method.
  - interestDelete
```
public void interestDelete()
```
    Called by the server library each time that it wishes to remove its subscription for PV value change events from the server tool via ProcessVariableEventCallback.postEvent() method.
  - read
```
public abstract CAStatus read(DBR value,
                              ProcessVariableReadCallback asyncReadCallback)
                       throws CAException
```
    Read process variable value. The request is allowed to complete asynchronously.
    The incoming DBR value is always (at least) of type DBR_TIME_[type] where type is of getType(). If DBR_GR_ or DBR_CTRL_ is requested then value is instance of requested type.
    
    Special cases:
    DBR_TIME_Enum type is "upgraded" to an "artificial" TIME type DBR_TIME_LABELS_Enum. This enables PV to set labels and time.
    DBR_TIME_Double and DBR_TIME_Float are "upgraded" to an "artificial" TIME type which also implements PRECISION interface, DBR_PRECISION_Double and DBR_PRECISION_Float. This enables PV to set precision (-1, by default, means no precision set).
    
    Parameters:
    
    value - value of type (at least) DBR_TIME_ where type is of getType().
    
    asyncReadCallback - if asynchronous completion is required method should return null and call ProcessVariableReadCallback.processVariableReadCompleted() method.
    
    Returns:
    
    CA status, null if request will complete asynchronously by calling method.
    
    Throws:
    
    CAException
  - write
```
public abstract CAStatus write(DBR value,
                               ProcessVariableWriteCallback asyncWriteCallback)
                        throws CAException
```
    Write process variable value. The request is allowed to complete asynchronously. The incoming DBR is always of type getType().
    
    Parameters:
    
    value - value of type getType().
    
    asyncWriteCallback - if asynchronous completion is required method should return null and call ProcessVariableWriteCallback.processVariableWriteCompleted() method.
    
    Returns:
    
    CA status, null if request will complete asynchronously by calling method.
    
    Throws:
    
    CAException
  - createChannel
```
public ServerChannel createChannel(int cid,
                                   int sid,
                                   String userName,
                                   String hostName)
                            throws CAException
```
    This method is called each time that a PV is attached to by a client. This method can be overriden to specialize access to PV (e.g. for particular client, setting access rights, ...).
    
    Parameters:
    
    cid - channel CID.
    
    sid - channel SID.
    
    userName - client user name.
    
    hostName - client host name.
    
    Returns:
    
    ServerChannel instance.
    
    Throws:
    
    CAException
  - registerChannel
```
public void registerChannel(ServerChannel channel)
```
    Register channel to this process variable.
    
    Parameters:
    
    channel - channel to register.
  - unregisterChannel
```
public void unregisterChannel(ServerChannel channel)
```
    Unregister channel from this process variable.
    
    Parameters:
    
    channel - channel to unregister.
  - destroy
```
public void destroy()
```
    Destory process variable. This method is called:
    - each time that a PV transitions from a situation where clients are attached to a situation where no clients are attached.
    - once for all PVs that exist when the server is deleted
  - printInfo
```
public void printInfo()
               throws IllegalStateException
```
    Prints detailed information about the Context to the standard output stream.
    
    Throws:
    
    IllegalStateException - if the context has been destroyed.
  - printInfo
```
public void printInfo(PrintStream out)
               throws IllegalStateException
```
    Prints detailed information about the Context to the specified output stream.
    
    Parameters:
    
    out - the output stream.
    
    Throws:
    
    IllegalStateException - if the context has been destroyed.
  - getEventCallback
```
public ProcessVariableEventCallback getEventCallback()
```
    Get event callback.
    
    Returns:
    
    the eventCallback
  - setEventCallback
```
public void setEventCallback(ProcessVariableEventCallback eventCallback)
```
    Set event callback.
    
    Parameters:
    
    eventCallback - the eventCallback to set

Class ProcessVariable

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

name

eventCallback

interest

channelCount

ackS

ackT

Constructor Detail

ProcessVariable

Method Detail

getName

getType

getMaxDimension

getDimensionSize

getEnumLabels

getAckS

setAckS

isAckT

setAckT

interestRegister

interestDelete

read

write

createChannel

registerChannel

unregisterChannel

destroy

printInfo

printInfo

getEventCallback

setEventCallback