# Error Handling
The **Error Event** is used to handle **exceptions or runtime errors** that occur during the execution of a task in a Microflow or Process Flow.\
It allows the flow to react gracefully to failures by executing **alternative logic**, such as logging errors, sending notifications, or triggering recovery actions.
***
### Purpose
**Error Events** are designed to:
* Capture and handle exceptions thrown during task execution
* Prevent abrupt termination of a flow
* Enable controlled error recovery or escalation logic
For example:
* If a **Java Task** throws an exception
* Or a **Web Service Task** fails during execution
An **Error Event** can be attached to handle the error by:
* Sending an error message or notification
* Logging error details
* Redirecting the flow to an alternate path
This makes Error Handling a critical component for building **robust and production‑ready integrations**.
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### Error Event as a Boundary Event
The Error Event is commonly used as a **Boundary Event**, attached to an Activity Node.
Behavior:
* The main task begins execution
* If an exception occurs within the task
* The Error Event is triggered
* The flow transitions to an error‑handling path
When an Error Event is triggered, the normal execution of the attached task is interrupted.
***
### Error Event Configuration
The **Error Configuration Panel** contains a single tab for defining error handling behavior.
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#### Error Tab
| Property | Mandatory | Default | Description |
| ------------- | --------- | ------- | ------------------------------------------------------------------ |
| **Exception** | Yes | — | Specifies the type of exception that the Error Event should handle |
***
### Managing Exceptions
Within the **Error** tab, users can manage exception handling rules using the following actions:
* **Add Exception Row**\
Add additional exception types to be handled by the Error Event.
* **Delete**\
Remove an existing exception configuration.
Multiple exception types can be associated with a single Error Event, allowing flexible and comprehensive error handling.
***
### Mapping Parameters for Error Handling
The **Open Mapping Parameter** button allows users to map data related to the exception.
When clicked:
1. The system navigates to the **Mapping Parameter Screen**
2. Users can configure:
* **Mapping Parameter Input** – pass data into the error‑handling path
* **Mapping Parameter Output** – capture error information for downstream logic
This enables:
* Detailed error reporting
* Conditional error handling based on exception data
* Propagating error context to other nodes
***
### Best Practices for Error Handling
* Always handle expected failure points (external services, databases, Java logic)
* Combine **Error Events** with **Timer Events** for robust timeout handling
* Avoid swallowing errors silently; log or notify appropriately
* Use descriptive exception mapping to improve troubleshooting
* Keep error‑handling logic clear and isolated
***
### Summary
The **Error Handling** mechanism in ONEWEB allows flows to respond predictably and safely to runtime failures.
By using **Error Events**, developers can:
* Detect and capture execution errors
* Prevent uncontrolled flow termination
* Execute recovery or escalation logic
* Improve reliability of integration workflows
Error Handling is essential for building **fault‑tolerant, enterprise‑grade integrations** in ONEWEB, especially when working with external systems and custom logic.
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