JSF and Database Validation

Question

I would like to perform validation that seems to be a little involved with JSF and I was curious as to the best practice. I need to perform validation on a summary screen where the user can highlight a row and click an Edit button that takes them to another screen. However, I need to query the database when they click edit to check to see if the item they selected is able to be edited (these rules are part of our business logic). What is the best way to perform database-side validation using JSF? If I query the DB in the action event of the command button, how can I then inform the JSP if the item fails validation and then display a message from messages. properties? Keep in mind that an item can fail validation for a number of reasons, so the message could be different each time the validation is performed.

Answer 1

You have two choices:
a) Don't let the user edit the line, by don't allowing the he to have an action on that row.
b) If you have a global command, then perform the validation on the action method.
In the a) case, you only have to put some flags to tell the page to not put the command on the row. This flags came with the query or whatsoever that you like more.
In the b) case you can perform the validation by calling the business logic, and in case of failiure, you can add a message to the FacesMessage tellong the user the reason of not allowing he to edit.
Example (on the bean):
FacesContext.getCurrentInstance().addMessage(componentId,
new FacesMessage(FacesMessage.SEVERITY_ERROR,
errorMessage,
errorMessage));
The componentId can be null or of not, the id of a component on the page.