JSF转换前保存输入值

Question

I have a input field where user enter their social security number(userid). This number has to be in a certain format so I use a custom converter to format it correctly. Later the number is checked against a DB. When the check fails, I want the number to be displayed the way the user entered it for UX reasons. But the conversion is before the check and the userid in the backing bean is set to the converted value, the original number is lost. What is the best way to save the original value?

<h:inputText id="userId" value="#{bean.userId}">
    <f:converter converterId="IdConverter" />
</h:inputText>

Answer 1

If I understand your problem correctly then you do not need to save the original value. Take advantage of the JSF lifecycle.

In addition to a custom converter, you would also need a custom validator. In your validator, if the check between the converted input and the data on the db is successful then the getAsString of your custom converter will simply return the converted input. However, if conversion succeeds but validation fails (meaning the check against the db record is unsuccessful) then you will simply throw a ValidatorException . The getAsString will not get called and the raw input will be displayed.

There are two ways that I can think of on how you can achieve this. For the first approach, you can define a validator method within your bean and move your validation logic in that method. Example :

public class Bean {    
    //Remainder omitted

    public void validate(FacesContext fc, UIComponent uic, Object o) {
        //Get the converted input. Assuming of type String
         String convertedInput = (String) o; 

        //Move the db check in this method. If it fails simply throw 
        //a ValidatorException like below. If it succeeds, don't return anything

        //throw new ValidatorException(new FacesMessage("Validation Failed")); 
    }
} 

Be mindful of the return type and the parameters.

Then you would add the validator attribute in the <h:inputText> like so

<h:inputText id="userId" value="#{bean.userId}" validator="#{bean.validate}">

One advantage with this approach is that this method will be able to access other instance variables of the Bean class but as a downside, it is less portable.

Another approach would be to have a separate class implement the Validator interface. Example:

@FacesValidator("customValidator")
public class MyValidator implements javax.faces.validator.Validator {

    @Override
    public void validate(FacesContext fc, UIComponent uic, Object o) {
        //Same logic as bean validator method
    }
}

Then add in your <h:inputText>

<f:validator validatorId="customValidator" />

You problem seems to indicate a lack of understanding of the JSF Lifecycle. I would highly suggest that you take the time to understand this concept as much as possible. You might not understand it in one sitting but as you get more involved with JSF, some aspects will become clearer. Here's a good place to start.

Debug JSF lifecycle