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Value change listener updating bean

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posted 16 years ago

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Howzit guys.

Ok here is an interesting one.

Below is a code sample of a value change listener. The example is a bit contrived, but is simple enough to explain my problem.

I got field on the form mapped to a String on my BB. This field is manadatory. (There's a reason for it). Also I have a drop down box on the page, whose value is mapped to a String on my BB. Lastly there are 2 extra fields on the page that display or hide based on the selection of the drop down box.

Now everything is working just fine. The trick is I don't want validation to happen when the onchange for the drop down is called. For that in the valueChangeListener method I renderResponse as soon as I have updated my beans flags. ie: FacesContext.getCurrentInstance().renderResponse(); without this validation on the mandatory field still happens, which I don't want.

Here comes the problem. Let's say each item in the my drop down value is 1, 2, and 3. I want to display this value is the mandatory field. Look at the valueChanged method to see what I'm trying to do. The problem is that the BB getters aren't called again when the page is rendered. Also, if I take the renderResponse out, in other words, get the rest of the components on the form to update the BB, then the setter is called for the component that I just set myself, and overwrites that value with what was filled in in the jsp.

If this is all not clear hopefully is becomes so when I post the code. Otherwise please shout.

Cheers
Darryl

Bean:

package valuechange;
 
import javax.faces.context.FacesContext;
import javax.faces.event.ValueChangeEvent;
 
public class ValueChangeBean {
  //value of the item selected from drop down
  private String selectedItem = "";
  //flags to render field1 and field2
  private boolean showField1;
  private boolean showField2;
  //this is the mandatory field, to be filled in with selectedItem value
  private String mandatoryField;
  
  public void valueChanged(ValueChangeEvent evt) {
    if (evt.getNewValue().equals("1")) {
      setShowField1(true);
      setShowField2(false);
    } else if (evt.getNewValue().equals("2")) {
      setShowField1(false);
      setShowField2(true);
    } else {
      setShowField1(true);
      setShowField2(true);
    }
    //TRYING TO SET VALUE OF MANDATORYFIELD here....
    mandatoryField = evt.getNewValue().toString();
    FacesContext.getCurrentInstance().renderResponse();
  }
  
  
 
  public String getSelectedItem() {
    return selectedItem;
  }
 
  public void setSelectedItem(String selectedItem) {
    this.selectedItem = selectedItem;
  }
  
  public boolean isShowField1() {
    return showField1;
  }
 
  public void setShowField1(boolean showField1) {
    this.showField1 = showField1;
  }
 
  public boolean isShowField2() {
    return showField2;
  }
 
  public void setShowField2(boolean showField2) {
    this.showField2 = showField2;
  }
 
  public String getMandatoryField() {
    return mandatoryField;
  }
 
  public void setMandatoryField(String mandatoryField) {
    this.mandatoryField = mandatoryField;
  }
}

JSP PAGE:

<%@ page isELIgnored="false" language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://myfaces.apache.org/tomahawk" prefix="t" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<f:view>
<head>
  <title>Value Change Tester</title>
</head>
<body>
 
  <h:form id="mainform">
<h:inputText id="mandField" value="#{changeBean.mandatoryField}" required="true"/>
<h:message id="msgMandField" for="mandField"/>
<p>
    <h:selectOneMenu id="scheduleType" value="#{changeBean.selectedItem}"
    onchange="submit()" valueChangeListener="#{changeBean.valueChanged}" immediate="true">
    <f:selectItem itemValue="1" itemLabel="Show Field 1"/>
  <f:selectItem itemValue="2" itemLabel="Show Field 2"/>
  <f:selectItem itemValue="3" itemLabel="Show Both"/>
    </h:selectOneMenu>
    <p>
    
    <h:inputText required="true" value="field1" rendered="#{changeBean.showField1}"/>
<br>
    <h:inputText required="true" value="field2" rendered="#{changeBean.showField2}"/>
    
  </h:form>
  
</div>
</body>
</f:view>
</html>

I understand what is happening. JSF is calling the setter of the mandatoryField after I have set the value, with the value filled in on the page, which is nothing, that's why it is being overwritten. My question is how do I get kind oif behavior to work??

Thanks
cheers
Darryl

Christophe Verré

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posted 16 years ago

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What about binding the input to your BB, and calling setSubmittedValue ?

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Darryl Nortje

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Posts: 140

posted 16 years ago

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Howzit Christopher,

Thanks for the solution. I'm sure it'll work. Will give it a try a bit later when I have more time.

In the mean time though, and out of interest, would this be possible without binding?

Cheers
Darryl

Sivalingam Sivasuthan

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Posts: 75

posted 14 years ago

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Thanks Christophe, I had the same issue solved by your solution.

- Siva<br /> Sun Certified Programmer for the Java™2 Platform

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