Compare two fields that use same class

问题

I have two input fields fromDate and toDate which are instances of Date class. The Date class uses custom Date validator which validates the month, day and year fields contained in the date field. The custom date validator is specific for each date i.e, fromDate and toDate. I need to compare the month, day or year fields of fromDate with toDate. If the fromDate is greater than toDate, a validation message has to displayed.

Update:

The fromDate and toDate are two custom date components as below

<eg:dateField id="inpFromDate" value="#{mrBean.fromDate}" .... />
<eg:dateField id="inpToDate" value="#{mrBean.toDate}" .... />

fromDate and toDate are instances of Date class which is

public class Date {
private String mm;
private String dd;
@customDateValidator   //Validates each date field
private String yyyy;
//constructors
//getters and setters

How would you implement the validator in this case where each date already has a validator

回答1:

Yes, you can! Suppose you have the following PrimeFaces's input fields:

<p:calendar id="from" value="#{mrBean.fromDate}" binding="#{from}" >
   <p:ajax process="from to" update="toDateMsg" />
</p:calendar>
<p:calendar id="to"   value="#{mrBean.toDate}" >
   <f:attribute name="fromDate" value="#{from.value}" />
   <f:validator validatorId="validator.dateRangeValidator" />
   <p:ajax process="from to" update="toDateMsg" />
</p:calendar>
<p:message for="to" id="toDateMsg" />

This should be your Validator:

@FacesValidator("validator.dateRangeValidator")
public class DateRangeValidator implements Validator {

    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        if (value == null || component.getAttributes().get("fromDate") == null) return;

        Date toDate   = (Date) value; 
        Date fromDate = (Date) component.getAttributes().get("fromDate");

        if (toDate.after(fromDate)) {
            FacesMessage message = new FacesMessage("Invalid dates submitted.");
            message.setSeverity(FacesMessage.SEVERITY_ERROR);
            throw new ValidatorException(message);
        }
    }
}

Note that I am using PrimeFaces's <p:calendar> component to write my example because the properties binded to this component will automatically be converted to Date object before being validated. In your program, you may have your own Converter to convert String to Date.

来源：https://stackoverflow.com/questions/8745731/compare-two-fields-that-use-same-class

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