gov.aps.epics.jca
Class Context

java.lang.Object
  |
  +--gov.aps.epics.jca.Context

All Implemented Interfaces:

CaConstants

Direct Known Subclasses:

JNIContext

public abstract class Context

extends java.lang.Object

implements CaConstants

The class representing a CA Context.

A Context controls all IO operations and the circuits thru which Channels will be created and connected. Since CA 3.14 an application can create more than one context, thus ehancing IO control and Channels managment. It is also possible for the application to specify how asynchronous callbacks will be provided by a context.

 Two differents mode are possible:
   ENABLE_PREEMPTIVE_CALLBACK : The callbacks are controled by independant threads. The application 
                                does not need to call pendEvent() to process pending event.
   DISABLE_PREEMPTIVE_CALLBACK: The callbacks are controled by the application itself which
                                need to call pendEvent() to process pending events.
 
 

In earlier CA version, only on context using the DISABLE_PREEMPTIVE_CALLBACK mode is allowed. The Context class also offers two different thread control mode.

   THREAD_CTRL_EXTERNAL: in this mode only the thread that created the Context (and all 
                         others that have registered with the Context) are allowed to perform
                         operations.
   THREAD_CTRL_INTERNAL: in this mode the Context uses its own internal thread to perform
                         operations, thus allowing any thread in the application to access the Context.

 

For complexity reasons uses THREAD_CTRL_EXTERNAL mode in simple application or in application where you want to control which threads will access the Context.

See Also:

Ca, CaConstants

Field Summary

protected static java.util.HashMap

_contextMap

Fields inherited from interface gov.aps.epics.jca.CaConstants

CA_K_ERROR, CA_K_FATAL, CA_K_INFO, CA_K_SEVERE, CA_K_SUCCESS, CA_K_WARNING, CA_M_ERROR, CA_M_LEVEL, CA_M_MSG_NO, CA_M_SEVERE, CA_M_SEVERITY, CA_M_SUCCESS, CA_OP_ADD_MONITOR, CA_OP_CLEAR_MONITOR, CA_OP_CONN_DOWN, CA_OP_CONN_UP, CA_OP_FIRST, CA_OP_GET, CA_OP_LAST, CA_OP_OTHER, CA_OP_PUT, CA_OP_SEARCH, CA_OP_STRING, CA_V_MSG_NO, CA_V_SEVERITY, CA_V_SUCCESS, CALLBACK_MODE_FIRST, CALLBACK_MODE_LAST, CALLBACK_MODE_STRING, CS_CLOSED, CS_CONN, CS_FIRST, CS_LAST, CS_NEVER_CONN, CS_PREV_CONN, CS_STRING, DBE_ALARM, DBE_LOG, DBE_VALUE, DBR_BYTE, DBR_CTRL_BYTE, DBR_CTRL_DOUBLE, DBR_CTRL_ENUM, DBR_CTRL_FLOAT, DBR_CTRL_INT, DBR_CTRL_SHORT, DBR_CTRL_STRING, DBR_DOUBLE, DBR_ENUM, DBR_FIRST, DBR_FLOAT, DBR_GR_BYTE, DBR_GR_DOUBLE, DBR_GR_FLOAT, DBR_GR_INT, DBR_GR_SHORT, DBR_GR_STRING, DBR_INT, DBR_LABELS_ENUM, DBR_LAST, DBR_PUT_ACKS, DBR_PUT_ACKT, DBR_SHORT, DBR_STRING, DBR_STS_BYTE, DBR_STS_DOUBLE, DBR_STS_ENUM, DBR_STS_FLOAT, DBR_STS_INT, DBR_STS_SHORT, DBR_STS_STRING, DBR_STSACK_STRING, DBR_TIME_BYTE, DBR_TIME_DOUBLE, DBR_TIME_ENUM, DBR_TIME_FLOAT, DBR_TIME_INT, DBR_TIME_SHORT, DBR_TIME_STRING, DBR_TYPE_STRING, DISABLE_PREEMPTIVE_CALLBACK, ECA_ADDFAIL, ECA_ALLOCMEM, ECA_ANACHRONISM, ECA_BADCHID, ECA_BADCOUNT, ECA_BADFUNCPTR, ECA_BADMASK, ECA_BADMONID, ECA_BADPRIORITY, ECA_BADSTR, ECA_BADSYNCGRP, ECA_BADTYPE, ECA_BUILDGET, ECA_CHANDESTROY, ECA_CHIDNOTFND, ECA_CHIDRETRY, ECA_CONN, ECA_DBLCHNL, ECA_DBLCLFAIL, ECA_DEFUNCT, ECA_DISCONN, ECA_DISCONNCHID, ECA_DLCKREST, ECA_EMPTYSTR, ECA_EVDISALLOW, ECA_FIRST, ECA_GETFAIL, ECA_INTERNAL, ECA_IODONE, ECA_IOINPROGRESS, ECA_ISATTACHED, ECA_LAST, ECA_MAXIOC, ECA_MESSAGE_STRING, ECA_NEEDSFP, ECA_NEWADDR, ECA_NEWCONN, ECA_NOCACTX, ECA_NOCAST, ECA_NOCHANMSG, ECA_NOCONVERT, ECA_NORDACCESS, ECA_NOREPEATER, ECA_NORMAL, ECA_NOSEARCHADDR, ECA_NOSUPPORT, ECA_NOTINSERVICE, ECA_NOTTHREADED, ECA_NOWTACCESS, ECA_OVEVFAIL, ECA_PUTCBINPROG, ECA_PUTFAIL, ECA_SERVBEHIND, ECA_SOCK, ECA_STRTOBIG, ECA_TIMEOUT, ECA_TOLARGE, ECA_UKNCHAN, ECA_UKNFIELD, ECA_UKNHOST, ECA_UKNSERV, ENABLE_PREEMPTIVE_CALLBACK, THREAD_CTRL_EXTERNAL, THREAD_CTRL_FIRST, THREAD_CTRL_INTERNAL, THREAD_CTRL_LAST, THREAD_CTRL_STRING

Constructor Summary

Context()

Method Summary

abstract void	attachCurrentThread()
gov.aps.epics.jca.Channel	createChannel(java.lang.String name) Create a new Channel using this context to access a process variable.
abstract gov.aps.epics.jca.Channel	createChannel(java.lang.String name, gov.aps.epics.jca.ConnectionListener l) Create a new Channel using this context to access a process variable with a ConnectionListener to receive ConnectionEvent from the newly created Channel.
abstract void	destroy() Destroys the Context and clear all associated ressources.
void	dispose()
abstract void	flushIO()
abstract int	getCallbackMode() Returns the Context's callback mode.
java.lang.String	getCallbackModeString() Returns a String representing the Context's callback mode.
abstract gov.aps.epics.jca.ContextExceptionListener	getContextExceptionListener() Returns the ContextExceptionListener registered with the Context.
static gov.aps.epics.jca.Context[]	getContextList() Returns all created Contexts.
abstract gov.aps.epics.jca.ContextMessageListener	getContextMessageListener() Returns the ContextMessageListener registered with the Context.
abstract java.lang.String	getName() Returns the name of the Context.
abstract int	getThreadCtrlMode() Returns the Context's thread control mode.
java.lang.String	getThreadCtrlModeString() Returns a String representing the Context's thread control mode.
protected static gov.aps.epics.jca.Context	lookupContext(java.lang.String name)
abstract void	pendEvent(double time) Process all pending events.
abstract void	pendIO(double timeout) Process all pending IO operations.
abstract void	poll()
void	printInfo() Prints detailed information about the Context to the standard output stream.
void	printInfo(java.io.PrintStream out) Prints detailed information about the Context to the specified output stream.
protected static void	registerContext(gov.aps.epics.jca.Context c)
abstract void	setContextExceptionListener(gov.aps.epics.jca.ContextExceptionListener l) Sets the ContextExceptionListener which will receive ContextExceptionEvents from this Context.
abstract void	setContextMessageListener(gov.aps.epics.jca.ContextMessageListener l) Sets the ContextMessageListener which will receive ContextMessageEvents from this Context.
abstract boolean	testIO() Tests if there are some pending IO requests.
protected static void	unregisterContext(gov.aps.epics.jca.Context c)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

_contextMap

protected static java.util.HashMap _contextMap

Constructor Detail

Context

public Context()

Method Detail

printInfo

public void printInfo()

Prints detailed information about the Context to the standard output stream.

printInfo

public void printInfo(java.io.PrintStream out)

Prints detailed information about the Context to the specified output stream.

Parameters:

out - the output stream.

registerContext

protected static void registerContext(gov.aps.epics.jca.Context c)

unregisterContext

protected static void unregisterContext(gov.aps.epics.jca.Context c)

lookupContext

protected static gov.aps.epics.jca.Context lookupContext(java.lang.String name)

getContextList

public static gov.aps.epics.jca.Context[] getContextList()

Returns all created Contexts.

dispose

public void dispose()

getName

public abstract java.lang.String getName()

Returns the name of the Context.

getThreadCtrlMode

public abstract int getThreadCtrlMode()

Returns the Context's thread control mode.

See Also:

CaConstants

getThreadCtrlModeString

public java.lang.String getThreadCtrlModeString()

Returns a String representing the Context's thread control mode.

See Also:

CaConstants

getCallbackMode

public abstract int getCallbackMode()

Returns the Context's callback mode.

See Also:

CaConstants

getCallbackModeString

public java.lang.String getCallbackModeString()

Returns a String representing the Context's callback mode.

See Also:

CaConstants

getContextMessageListener

public abstract gov.aps.epics.jca.ContextMessageListener getContextMessageListener()

Returns the ContextMessageListener registered with the Context.

setContextMessageListener

public abstract void setContextMessageListener(gov.aps.epics.jca.ContextMessageListener l)
                                        throws CaException

Sets the ContextMessageListener which will receive ContextMessageEvents from this Context.

Parameters:

l - the ContextMessageListener.

CaException

getContextExceptionListener

public abstract gov.aps.epics.jca.ContextExceptionListener getContextExceptionListener()

Returns the ContextExceptionListener registered with the Context.

setContextExceptionListener

public abstract void setContextExceptionListener(gov.aps.epics.jca.ContextExceptionListener l)
                                          throws CaException

Sets the ContextExceptionListener which will receive ContextExceptionEvents from this Context.

Parameters:

l - the ContextExceptionListener.

CaException

destroy

public abstract void destroy()
                      throws CaException

Destroys the Context and clear all associated ressources.

CaException

createChannel

public gov.aps.epics.jca.Channel createChannel(java.lang.String name)
                                        throws CaException

Create a new Channel using this context to access a process variable.

Parameters:

name - the process variable to connect to.

Returns:

the new Channel.

CaException

createChannel

public abstract gov.aps.epics.jca.Channel createChannel(java.lang.String name,
                                                        gov.aps.epics.jca.ConnectionListener l)
                                                 throws CaException

Create a new Channel using this context to access a process variable with a ConnectionListener to receive ConnectionEvent from the newly created Channel.

Parameters:

name - the process variable to connect to.

l - the ConnectionListener.

Returns:

the new Channel.

Throws:

CaException - is thrown if the Context has been destroyed.

pendIO

public abstract void pendIO(double timeout)
                     throws CaException

Process all pending IO operations.

Parameters:

timeout - the timeout limit.

Throws:

CaException - is thrown if all the IO couldn't be processed.

CaException - is thrown if the Context has been destroyed.

testIO

public abstract boolean testIO()
                        throws CaException

Tests if there are some pending IO requests.

CaException

pendEvent

public abstract void pendEvent(double time)
                        throws CaException

Process all pending events.

Parameters:

time - the time during which the Context will process events.

CaException

poll

public abstract void poll()
                   throws CaException

CaException

flushIO

public abstract void flushIO()
                      throws CaException

CaException

attachCurrentThread

public abstract void attachCurrentThread()
                                  throws CaException

CaException