Struts 2 INPUT Result: How are Conversion and Validation Errors Handled, and Why is an INPUT Result Returned Instead of an Exception?

Struts2 INPUT Result: How it Works? How Are Conversion/Validation Errors Handled?

Main Question

When an invalid string is entered instead of a number, it should pass through the Exception Interceptor. During the Param Interceptor, converting to an int type using Integer.parseInt should fail, triggering a NumberFormatException. Shouldn't this exception be pushed into the Value Stack? Why is the result shown despite errors?

Side Question

Entering alphabets in the form results in zero being displayed. Why is this?

Concept

Struts2 treats conversion and validation errors as input errors rather than blocking errors. Instead of raising exceptions, it returns an INPUT result and notifies the user of incorrect input.

Detailed Workflow

1. Parameters Interceptor: Tries to set parameters. If a RuntimeException (e.g., NumberFormatException) occurs in devMode, an error message is added to the Action Errors. Otherwise, the exception is suppressed.
2. Conversion Errors Interceptor: Checks for conversion errors and adds Field Errors for any found. It also saves original values to display them in subsequent requests.
3. Validation Interceptor: Performs requested validations and adds Field Errors for fields not meeting criteria.
4. Workflow Interceptor: Checks for Field Errors. If none are found, the chain continues. If errors exist, an INPUT result is returned.

Side Question Answer

In the original answer, conversion errors resulted in zero due to retrieving the default int value instead of the String input. However, Conversion Interceptor should have saved the original string to display it in subsequent requests.

But why is the string displayed as zero instead of abc?

The issue is caused by the value attribute in the input component. Using getText() or getText() in the value attribute results in conversion issues. Removing the value attribute or using %{myIntField} solves the problem.

Conclusions

• Ensure the Interceptor Stack is properly configured.
• Check the value attribute in input components.
• Remove the value attribute for testing purposes to verify correct behavior.

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