Canvas Exceptions

The Canvas namespace contains exception classes.

All exception classes support built-in methods for returning the error message and exception type. See Exception Class and Built-In Exceptions.

The Canvas namespace contains this exception:

Exception	Description
`Canvas.CanvasRenderException`	Use this class in your implementation of Canvas.CanvasLifecycleHandler.`onRender(renderContext)`. To show an error to the user in your `onRender()` implementation, throw a `Canvas.CanvasRenderException`, and the canvas framework will render the error message to the user. This exception will be managed only within the `onRender()` method.

Example

The following example implementation of onRender() catches a CanvasException that was thrown because a canvas URL was set with a string that exceeded the maximum length. A CanvasRenderException is created and thrown to display the error to the user.

public with sharing class MyCanvasListener 
implements Canvas.CanvasLifecycleHandler {
    
    public void onRender(Canvas.RenderContext renderContext) {
        Canvas.ApplicationContext app = renderContext.getApplicationContext();

        // Code to generate a URL string that is too long

        // ...

        // Try to set the canvas app URL using the invalid URL string
        try {
            app.setCanvasUrlPath(aUrlPathThatIsTooLong);
        } catch (CanvasException e) {
            // Display error to user by throwing a new CanvasRenderException
            throw new Canvas.CanvasRenderException(e.getMessage());
        }
    }
}

See the Canvas Developer Guide for additional examples that use CanvasRenderException.