Many times Developers are tempted to write their own validations.
If using Java, better to use “Commons Validator”
1. Always check for null. Don’t assume that customer will provide data.
2. Always check for boundary values….i.e min/max/…etc
3. Better to associate Error Messages with Error Codes. Pretty much required for Automation.
4. Externalize Strings to support multi lingual support
5. If not doing anything, don’t catch exceptions.
6. Don’t swallow exceptions….preserve the stack trace
7. Don’t convert exception A to exception B
8. Use Sonar and fix the values
9. Define constants separately….if possible configurable in future.