User Story

As a ZK app developer using comet server push, I want the XMLHttpRequest event handling to use modern APIs and be easily extensible. So that I can handle different request states (timeouts, network errors, etc.) without complex override patterns

Acceptance Criteria

1. Modern XMLHttpRequest Event Handling
   • GIVEN a comet server push request is initiated
   • WHEN the request completes, times out, errors, or is aborted
   • THEN dedicated event handlers should be called instead of generic onreadystatechange

       // Proposed modern approach
       req.onload = this._onLoad.bind(this);
       req.onerror = this._onError.bind(this);
       req.ontimeout = this._onTimeout.bind(this);
       req.onabort = this._onAbort.bind(this);
     

2. Extensible Event Handler Architecture
   • GIVEN developers need custom request handling behavior
   • WHEN they want to override specific event types
   • THEN they should be able to override single funciton
3. Event Classification and Context
   • GIVEN different types of request events occur
   • WHEN handlers are invoked
   • THEN they should receive rich context about the event type and state
4. Backward Compatibility
   • GIVEN existing ZK applications use the current API
   • WHEN this feature is implemented
   • THEN existing behavior should remain unchanged by default
   • AND new behavior should be opt-in via configuration
5. Put XMLHttpRequestino creation in an independent function
   • allow to be overridden

Details

• The current SPush implementation in /zkcml/zkex/src/main/resources/web/js/zkex/cmsp/serverpush.ts uses legacy XMLHttpRequest event handling:

  // Current (legacy approach)
  req.onreadystatechange = this._onRespReady.bind(this);
  req.onabort = this._retry.bind(this) as never;
  // Missing: ontimeout, onerror handlers

This causes several issues:

• Expected timeouts are treated as errors, incrementing fail counters
• Network errors and timeouts can't be distinguished
• Developers need complex zk.override() patterns to customize behavior
• Mixed old/new event paradigms create inconsistent behavior