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POValuechangelistener Doubt in JSF
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  1. POValuechangelistener Doubt in JSF
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    copied!<p>HI,</p> <p>Please see the following code:</p> <pre><code> &lt;h:selectOneMenu id="countries" value="#{countryBean.selectedCountry}" onchange="submit() valueChangeListener="#{countryBean.changeCountry}"&gt; &lt;f:selectItems value="#{countryBean.countries }" /&gt; &lt;/h:selectOneMenu&gt; </code></pre> <p><strong>Backing Bean</strong></p> <pre><code>public void changeCountry(ValueChangeEvent event){ String newValue = (String)event.getNewValue(); String oldValue = (String)event.getOldValue(); System.out.println("New Value : " + newValue); System.out.println("Old Value : " + oldValue); if ("1".equals(newValue)){ this.countries = new ArrayList&lt;SelectItem&gt;(); this.cities.add(new SelectItem("1","Delhi")); this.cities.add(new SelectItem("2","Mumbai")); } if ("2".equals(newValue)){ this.cities = new ArrayList&lt;SelectItem&gt;(); this.cities.add(new SelectItem("1","Mossco")); } } </code></pre> <p>Please let me know if the implementation is correct. It is working fine. My questions are:</p> <ul> <li>What is the advantage of adding the <em>f:valueChangeListener</em> tag inside the <em>h:selectOneMenu</em> tag. I have used the normal attribute valueChangeListener="#{countryBean.changeCountry}". </li> <li>Is it necessary to use <em>onchange="submit()</em> this code to change the values.</li> <li>What is difference between writing the custom listeners by implementing the ActionListener interface and just using the attribute in the UIComponent tags (action="methodName"). Please explain me.</li> </ul>
 

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