How Does Struts2\'s INPUT Result Handle Conversion and Validation Errors?

Struts2 INPUT Result: Mechanisms for Error Handling

Struts2's INPUT result offers a seamless method for handling conversion and validation errors without triggering exceptions. Here's how it operates:

Conversion Error Handling

When String is entered instead of an int, the Parameters Interceptor attempts conversion. If Integer.parseInt() encounters a NumberFormatException, the exception is suppressed in development mode, and an error message is added to the Action Errors. In production mode, the exception is silently ignored.

The Conversion Errors Interceptor subsequently checks for conversion errors. If any are identified, Field Errors are added, and the input value is stored to be displayed to the user during subsequent requests.

Validation Error Handling

The Validation Interceptor executes necessary validations based on XML or Annotations. Validation errors add Field Errors to the action. This ensures that errors are displayed to the user and the form is re-populated with the original values.

Workflow and INPUT Result

The Workflow Interceptor examines Field Errors. Upon encountering any errors, it returns an INPUT result. This result re-displays the form, preserving the original input values and error messages.

Handling Alphabets and Zeroes

The framework handles this scenario gracefully. When an alphabetic character is entered, the Conversion Interceptor saves its original value. The subsequent Getter will return the original value (e.g., "abc") instead of its numeric equivalent (e.g., "0").

Troubleshooting Conversion Errors

If not working as expected, ensure Interceptors are in the correct order and verify the value attribute. Avoid using it, if possible, for conversion purposes. Use it instead to preserve state, such as storing a placeholder value.

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