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Express Exception Handler ​

This guide explains how to integrate Lens's exception watcher with your Express application to monitor and report exceptions.

Configuration ​

First, ensure the exceptionWatcherEnabled option is set to true when initializing Lens. This option is enabled by default, but it's good practice to confirm its status in your configuration:

ts
const { handleExceptions } = await lens({
  // ... other options
  exceptionWatcherEnabled: true, // Ensure this is true to enable exception watching
});

Integration ​

Lens leverages Express Error Handling. You should call the handleExceptions function after all your routes are defined. This ensures that Lens can catch and process any exceptions that occur within your route handlers.

ts
// All routes are defined above

handleExceptions(app);

app.listen(port, () => {
  console.log(`Server is running at http://localhost:${port}`);
});

Verification ​

To verify that the exception handler is working correctly, you can intentionally throw an exception in one of your routes:

ts
app.get("/throw-error", async (_, res) => {
    throw new Error("Something went wrong");
});

After triggering this route, navigate to the Lens /exceptions path in your browser, and you should see the details of the captured exception.