TagHistoryLicense

java.lang.Object
- com.inductiveautomation.gateway.tags.history.module.TagHistoryLicense

All Implemented Interfaces:

LicenseStateUpdateListener, java.util.EventListener
```
public class TagHistoryLicense
extends java.lang.Object
implements LicenseStateUpdateListener
```
This class is used to manage tag history licensing. The only tricky aspect of it is that due to historical reasons, it also checks a platform feature that allows tag history.
There are static functions for retrieving state. However, it is better to use create() to get an instance, which will subscribe to various system, update the state, and cache it for better performance.
In 8.1, we decided to start protected all tag history functionality with the module. Historically, querying was free, and it can still be, but we should probably require a license in order to do it. We have introduced a new "limited" edition for that reason.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`canQuery()`
`boolean`	`canStore()`
`static TagHistoryLicense`	`create(GatewayContext context)`	I prefer this static creation in order to avoid implying the adding of listeners in the constructor.
`static boolean`	`isActive(GatewayContext context)`	Returns whether tag history is available and not demo expired.
`void`	`licenseStateUpdated(LicenseStateUpdateEvent e)`	The LicenseState for the module specified in the LicenseStateChangeEvent has been updated.
`protected void`	`refreshState()`
`void`	`shutdown()`

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

- Method Detail
  - create
```
public static TagHistoryLicense create(GatewayContext context)
```
    I prefer this static creation in order to avoid implying the adding of listeners in the constructor. That is, it balances shutdown()
  - shutdown
```
public void shutdown()
```
  - canStore
```
public boolean canStore()
```
  - canQuery
```
public boolean canQuery()
```
  - licenseStateUpdated
```
public void licenseStateUpdated(LicenseStateUpdateEvent e)
```
    Description copied from interface: LicenseStateUpdateListener
    
    The LicenseState for the module specified in the LicenseStateChangeEvent has been updated. Module id of empty-string represents the license state for the Ignition platform itself.
    
    Specified by:
    
    licenseStateUpdated in interface LicenseStateUpdateListener
    
    Parameters:
    
    e - The LicenseStateUpdateEvent
  - refreshState
```
protected void refreshState()
```
  - isActive
```
public static boolean isActive(GatewayContext context)
```
    Returns whether tag history is available and not demo expired.