Refresh JSF validator attributes on rerender - jsf

Question

I have an issue with the attributes values of a validator component.
Apparently the validator is created when I first visit a page.
Please see my code below:
<h:inputText value="#{qsetting.value}" rendered="#{qsetting.dataType=='Double'}">
<mw:validateRange min="#{qsetting.minValue}" max="#{qsetting.maxValue}" />
</h:inputText>
The inputText component is rerendered through ajax but apparently, including the value that is displayed.
Unfortunately, the qsetting.minValue and qsetting.maxValue are not refreshed, causing my validator to not work correctly.
Is there a possibility to refresh the validator, to make sure it re-retrieves its attributes or to just create a new instance of the validator?
The validator class itself is currently implementing "Validator, Serializable".
Also, I'm using jsf1.2 with facelets...
Thanks,
Steven

Answer 1

I've hit this problem in a non-ajax environment a few times over the years, and hit it again today. The addition of Ajax doesn't really change anything since a validator attribute is never evaluated again once the page is initially built, ajax or otherwise.
The only solution I've come up with is to set the validator attribute to a validator expression, then evaluate that expression inside the validate method.
One other issue I hit (also with JSF 1.2 and Facelets) is that not all EL variables worked. I had to use a static managed bean as the root of my expression to access the value. A facelet ui:param value as a root would not work. I haven't tested to see what else may not correctly evaluate. This could be due to another bug in the design of JSF itself. See http://myfaces.apache.org/core12/myfaces-api/apidocs/javax/faces/context/FacesContext.html#getELContext%28%29.
For example, instead of:
max="#{qsetting.maxValue}"
use
maxExpression="qsetting.maxValue"
Then
public String getMax(FacesContext context) {
Application app = context.getApplication();
ExpressionFactory exprFactory = app.getExpressionFactory();
ValueExpression ve = exprFactory.createValueExpression(context.getELContext(),
"#{" + getMaxExpression() + "}",
String.class);
Object result = ve.getValue(context.getELContext());
return (String)result;
}
public String getMaxExpression() {
return this.maxExpression;
}
public void setMaxExpression(String maxExpression) {
this.maxExpression = maxExpression;
}
//// StateHolder
public boolean isTransient() {
return isTransient;
}
public void setTransient(boolean newTransientValue) {
isTransient = newTransientValue;
}
public Object saveState(FacesContext context) {
Object[] state = new Object[1];
state[0] = maxExpression;
return state;
}
public void restoreState(FacesContext context, Object state) {
Object[] values = (Object[]) state;
maxExpression = (String) values[0];
}
UPDATE 2012-09-19:
After investigating how MyFaces Commons solves this problem, the better solution is to change the rules Facelets uses to evaluate validator and converter attribute expressions.
It basically comes down to adding a new validator or converter MetaRule which, when applied, checks to see if the attribute value is non-literal. If it is non-literal, call a special method on your validator or converter which passes in the value expression rather than the current value.
http://svn.apache.org/viewvc/myfaces/commons/trunk/myfaces-commons-validators/src/main/java/org/apache/myfaces/commons/validator/_ValidatorRule.java?view=markup
The validator at that point needs to store the value expression as state and evaluate it when needed. MyFaces commons provides all of the complicated infrastructure to make this happen generically, but you could dump all of that and write a simple custom rule and directly manage the ValueExpression yourself, similar to what I originally posted.