OpcItem

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dk.opi.io.opc.opcclient
Class OpcItem

java.lang.Object
  dk.opi.io.DefaultIOItem
      dk.opi.io.opc.opcclient.OpcItem

All Implemented Interfaces:: IOItem

public class OpcItem
extends DefaultIOItem

This class implements functinality related to items. An items represents the input/output points read/written to/from the devices monitored by the OPC server.

This class has no public constructor - use the OpcGroup.addItem() method to create instances of this class.

See Also:: OpcGroup.addItem(java.lang.String, java.lang.String, boolean, int, java.lang.String)

Field Summary
`protected boolean`	`invalid` This value is set to true if this item has been invalidated - ie. if it has been removed from the OPC server
`protected Object`	`oldChangeValue`

Fields inherited from class dk.opi.io.DefaultIOItem

actionCommand, active, dataType, description, GOOD_QUALITY_VALUE, ioGroup, name, oldValue, userObject

Fields inherited from interface dk.opi.io.IOItem

CACHE_READ, DATATYPE_BOOL, DATATYPE_BOOLARRAY, DATATYPE_DATE, DATATYPE_DOUBLE, DATATYPE_DOUBLEARRAY, DATATYPE_FLOAT, DATATYPE_FLOATARRAY, DATATYPE_INT, DATATYPE_INTARRAY, DATATYPE_STRING, DATATYPE_USE_NATIVE, DEVICE_READ

Method Summary
`IOQuality`	`getOldQuality()` Returns the quality of the last read value, ie. quality corresponding to the item value returned from calling `DefaultIOItem.getOldValue()` For efficiency reasons the same static IOQuality object is being reused when quality is good, ie. sub-status and limit value for good values will always be `IOQuality.GOOD_NON_SPECIFIC` and `IOQuality.LIMIT_NOT_LIMITED` respectively
`boolean`	`isInvalid()` Get the value of invalid.
`boolean`	`isOldQualityGood()` Returns quality of last read value.
`Object`	`readValue()` Read the item value from the device.
`Object`	`readValue(int dataSource)` Read the item value from the device.
`void`	`writeIntValue(int value)` Deprecated. Replaced by writeValue(int).
`void`	`writeValue(boolean value)` Write the specified value to the device.
`void`	`writeValue(Boolean value)` Write the specified value to the device.
`void`	`writeValue(boolean[] values)` Write the specified array of booleans to the device.
`void`	`writeValue(double value)` Write the specified value to the device.
`void`	`writeValue(double[] values)` Write the specified array of doubles to the device.
`void`	`writeValue(float value)` Write the specified value to the device.
`void`	`writeValue(float[] values)` Write the specified array of floats to the device.
`void`	`writeValue(int value)` Write the specified value to the device.
`void`	`writeValue(int[] values)` Write the specified array of integers to the device.
`void`	`writeValue(String value)` Write the specified value to the device.

Methods inherited from class dk.opi.io.DefaultIOItem

getActionCommand, getDataType, getDescription, getGroup, getOldValue, getUserObject, isActive, setActionCommand, setDescription, setOldValue, setUserObject, toString, writeValue, writeValue, writeValue

Methods inherited from class java.lang.Object

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

Field Detail

oldChangeValue

protected Object oldChangeValue

invalid

protected boolean invalid

This value is set to true if this item has been invalidated - ie. if it has been removed from the OPC server

Method Detail

readValue

public Object readValue()
                 throws RbxIOException

Read the item value from the device. The value is converted into an object corresponding to the dataType of this item.
The item value is read from the OPC server cache. This is fast but the value is only updated with the specified update rate, ie. A CACHE read is accurate to within the 'UpdateRate' of the group.

Specified by:: readValue in interface IOItem
Specified by:: readValue in class DefaultIOItem

Returns:: the value read from the item. The object returned are either of type Integer, Boolean etc. depending on the datatype of the item
Throws:: RbxIOException - thrown if the read operation failed

readValue

public Object readValue(int dataSource)
                 throws RbxIOException

Read the item value from the device. The value is converted into an object corresponding to the dataType of this item.

Specified by:: readValue in interface IOItem
Overrides:: readValue in class DefaultIOItem

Parameters:: dataSource - The source to read from, ie. CACHE_READ or DEVICE_READ. A cache read will obtain the current value for the item from the device server cache (ie. OPC server). This is fast but the value is only updated with the specified update rate. A CACHE read is accurate to within the 'UpdateRate' of the group.
The data can be read from the DEVICE in which case an actual read of the physical device is to be performed. The intended use of a DEVICE read is to update the register value of an inactive item. The exact implementation of CACHE and DEVICE reads may vary between devices and communication servers.
For CACHE reads the data is only valid if both the group and the item are active. DEVICE reads are not affected by the ACTIVE state of the group or item.
Returns:: the value read from the item. The object returned are either of type Integer, Boolean etc. depending on the datatype of the item
Throws:: RbxIOException - thrown if the read operation failed

writeIntValue

public void writeIntValue(int value)
                   throws RbxIOException

Deprecated. Replaced by writeValue(int).

Write the specified value to the device. The value written is supplied as an integer

Specified by:: writeIntValue in interface IOItem
Specified by:: writeIntValue in class DefaultIOItem

Parameters:: value - The value to send to the device
Throws:: RbxIOException - thrown if the write operation failed