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Input and output adapters to Esper provide the means of accepting events from various sources, and for making available events to destinations.
Esper has a fully-evolved API and natively accepts various input event formats and natively produces various output event objects, as part of core Esper.
It is therefore not necessary to use any of the adapters listed herein. Simply use the public Esper APIs directly in your code.
Most adapters present their own configuration as well as API. Some adapters also provide operators for use in data flows.
The Adapter interface allows client applications to control the state of an input and output adapter. It provides state transition methods that each
input and output adapter implements.
An input or output adapter is always in one of the following states:
Opened - The begin state; The adapter is not generating or accepting events in this state
Started - When the adapter is active, generating and accepting events
Paused - When operation of the adapter is suspended
Destroyed
The state transition table below outlines adapter states and, for each state, the valid state transitions:
Table 1.1. Adapter State Transitions
| Start State | Method | Next State |
|---|---|---|
| Opened | start() | Started |
| Opened | destroy() | Destroyed |
| Started | stop() | Opened |
| Started | pause() | Paused |
| Started | destroy() | Destroyed |
| Paused | resume() | Started |
| Paused | stop() | Opened |
| Paused | destroy() | Destroyed |