~~ specific language governing permissions and limitations
~~ under the License.

 ---
 Legacy Artifact Handlers Reference
 ---
 Hervé Boutemy
 ---
 2013-08-02
 ---

Legacy Artifact Handlers Reference

  Maven 3 artifact handlers (see {{{../maven-artifact/apidocs/org/apache/maven/artifact/handler/ArtifactHandler.html} API}})

## Handlers & Routes

Handlers have a predefined Handler ID. 
In addition, there can be several *static* subroutes used to differentiate between different handlers of the same ID.
A subroute on a client must match a subroute on the server. So routes cannot be used for dynamic routing, unlike HTTP.

## Override the default exception handlers

**FastAPI** has some default exception handlers.

These handlers are in charge of returning the default JSON responses when you `raise` an `HTTPException` and when the request has invalid data.

You can override these exception handlers with your own.

### Override request validation exceptions

{!../../../docs_src/events/tutorial001.py!}
```

In this case, the `startup` event handler function will initialize the items "database" (just a `dict`) with some values.

You can add more than one event handler function.

And your application won't start receiving requests until all the `startup` event handlers have completed.

### `shutdown` event

  // handler specifies the underlying runtime and configuration that the CRI
  // implementation will use to handle pods of this class. The possible values
  // are specific to the node & CRI configuration.  It is assumed that all
  // handlers are available on every node, and handlers of the same name are
  // equivalent on every node.
  // For example, a handler called "runc" might specify that the runc OCI

    opt raise
        dep -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        dep -->> dep: Raise other exception
    end
    dep ->> operation: Run dependency, e.g. DB session
    opt raise
        operation -->> dep: Raise HTTPException
        dep -->> handler: Auto forward exception
        handler -->> client: HTTP error response

Construction should create informers (via `kclient.New`), setup a queue (via `controllers.NewQueue`), and register event handlers on the informers.
Often, these handlers are adding something to the queue like `client.AddEventHandler(controllers.ObjectHandler(queue.AddObject))`.
Construction should NOT actually start running all of these things, do I/O, or block in anyway.

This was changed in version 0.110.0 to fix unhandled memory consumption from forwarded exceptions without a handler (internal server errors), and to make it consistent with the behavior of regular Python code.

  // handler specifies the underlying runtime and configuration that the CRI
  // implementation will use to handle pods of this class. The possible values
  // are specific to the node & CRI configuration.  It is assumed that all
  // handlers are available on every node, and handlers of the same name are
  // equivalent on every node.
  // For example, a handler called "runc" might specify that the runc OCI

  // CRI implementation will use to handle pods of this class. The possible
  // values are specific to the node & CRI configuration.  It is assumed that
  // all handlers are available on every node, and handlers of the same name are
  // equivalent on every node.
  // For example, a handler called "runc" might specify that the runc OCI