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JavaServer Faces: Common Mistakes

JavaServer Faces: Common Mistakes. Compiled from courses.coreservlets.com. Pressing Button and Nothing Happens. In JSF1, many error conditions simply result in the system redisplaying the form  JSF2 gives better help! No error messages or warnings

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JavaServer Faces: Common Mistakes

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  1. JavaServer Faces: Common Mistakes Compiled from courses.coreservlets.com

  2. Pressing Button and NothingHappens • In JSF1, many error conditions simply result in the system redisplaying the form  JSF2 gives better help! • No error messages or warnings • Very confusing to beginning developers • Debugging strategies for these situations • Many of the errors cause the process to abort at certain points. Knowing how far things got is very helpful. • Use print statements or IDE breakpoints • in the controller method • in the empty constructor • public MyBean() { System.out.println("MyBean built"); } • in the bean setter methods

  3. Pressing Button and NothingHappens: Common Cases • Return value of controller method does not match from-outcome of navigation-case • Remember values are case sensitive • Controller method returns null • This is often done on purpose to redisplay the form, but can be done accidentally as well. • Type conversion error • You declare field to be of type int, but value is not an integer when you submit. • Validation error • You declare field to be required and/or of certain length, but no/incorrect value is given when you submit. • Missing getter/setter method • You associate textfield with bean property foo, but there is no set/getFoomethod in your bean.

  4. Other Common Cases • Using from-action instead of from-outcome • Forgetting # in action of h:commandButton • Typo in from-view-id • Missing h:form • If you use h:inputText with no surrounding h:form, textfields will still appear but nothing will happen when you press submit button Use IDE’s autocomplete feature to help!

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