Duplicate call

Question

I have been coding in JSF for 2/3 years now, but never read a book on, been learning as I go. I do have a book now to try further my understanding of what happens behind the scenes but I'm rather perplexed at this code below, I can not understand why it does what it does. This is my code, it is list of email addresses which are displayed and can be modified, added to, delete...
JSF
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<f:view>
<h:form id="updateForm">
     <h:dataTable value="#{FeedbackReceiversHandler.receivers}" var="receiver"
          headerClass="headerBlue" rowClasses="white, altbg"
          border="0" cellpadding="3" cellspacing="0" width="500">
          <h:column>
               <f:facet name="header">
                    <h:outputText value="Id" />
               </f:facet>
               <h:outputText value="#{receiver.id}" />
          </h:column>
          <h:column>
               <f:facet name="header">
                    <h:outputText value="Check Details" />
               </f:facet>
               <h:inputText value="#{receiver.email}" />
          </h:column>
          <h:column>
               <f:facet name="header">
                    <h:outputText value="Enabled" />
               </f:facet>
               <h:selectBooleanCheckbox value="#{receiver.enabled}" />
          </h:column>
          <h:column>
               <f:facet name="header">
                    <h:outputText value="Preference" />
               </f:facet>
               <h:selectOneMenu id="preference" value="#{receiver.preference}">
                    <f:selectItem id="item1" itemLabel="Daily" itemValue="DAILY" />
                    <f:selectItem id="item2" itemLabel="Monday" itemValue="MONDAY" />
                    <f:selectItem id="item3" itemLabel="Tuesday" itemValue="TUESDAY" />
                    <f:selectItem id="item4" itemLabel="Wednesday" itemValue="WEDNESDAY" />
                    <f:selectItem id="item5" itemLabel="Thursday" itemValue="THURSDAY" />
                    <f:selectItem id="item6" itemLabel="Friday" itemValue="FRIDAY" />
               </h:selectOneMenu>
          </h:column>
          <h:column>
               <h:commandLink id="deleteReceiver" action="#{FeedbackReceiversHandler.delete}">
                    <h:graphicImage id="deleteImg" value="/images/delete.gif" alt="Remove email receiver" />
                    <f:param name="receiverId" value="#{receiver.id}" />
               </h:commandLink>
          </h:column>
     </h:dataTable>
     <h:commandButton id="save" action="#{FeedbackReceiversHandler.saveChanges}" value="Save Changes" />
</h:form>
</f:view>
Managed Bean
public class FeedbackReceiversHandler extends BaseBean {
     private static final Logger logger = Logger.getLogger(FeedbackReceiversHandler.class.getName());
     private ArrayList<ReceiverVO> receiversData;
     public ArrayList<ReceiverVO> getReceivers() {
          logger.debug("Get List Data...");
          receiversData = new ArrayList<ReceiverVO>();
          System.out.println("CALLED");
          Connection conn = null;
          ResultSet rs = null;
          PreparedStatement ps = null;
          try {
               conn = PooledConnectionHelper.getConnection("DS_WFMT_DATA");
               if (conn != null) {
                    logger.debug("Attempting to execute SQL: " + buildSQL());
                    ps = conn.prepareStatement(buildSQL());
                    // bind the variables
                    ps.setString(1, getPerspective());
                    rs = ps.executeQuery();
                    // Add each rows data into a data bean object and place into bean
                    while (rs.next()) {
                         ReceiverVO oneRecord = new ReceiverVO();
                         oneRecord.setId(rs.getString("RECEIVER_ID"));
                         oneRecord.setEmail(rs.getString("EMAIL"));
                         oneRecord.setEnabled(rs.getString("ENABLED").equalsIgnoreCase("Y"));
                         oneRecord.setPreference(rs.getString("PREFERENCE"));
                         receiversData.add(oneRecord);
          } catch (Exception ex) {
               logger.error("FAILED TO EXECUTE SQL: " + ex);
          } finally {
               PooledConnectionHelper.closeAllDatabaseObjects(conn, rs, ps);
          logger.debug("List of rows return contains "+ receiversData.size() +" records");
          return receiversData;
     private static String buildSQL() {
          // Main SQL to return all rows data for Records Return search without search criteria where clause
               SELECT
                    receiver_id,
                    email,
                    enabled,
                    preference
               FROM
                    feedback_receivers
               WHERE
                    perspective = ?
          final String RETVAL = "SELECT receiver_id, email, enabled, preference FROM feedback_receivers WHERE perspective = ?";
          return RETVAL;
     }What I can not understand is why the getReceivers() method gets called twice??? I have added System.outs into this method and also run the code through in debug mode in Eclipse so I know this get called twice when the page loads. What I don't know is why, and how do I stop this.
Depending on how fast the getReceivers() method runs, I very often get duplicate rows displayed which is the problem, plus even if it does display ok, it still means the database is getting hit twice.
Q's
1) So my questions are, why is this called twice?
2) How do I stop it being called twice?
TIA,
Dale Ellis

Answer 1

Dale_Ellis wrote:
What I can not understand is why the getReceivers() method gets called twice??? I have added System.outs into this method and also run the code through in debug mode in Eclipse so I know this get called twice when the page loads. What I don't know is why, and how do I stop this.Bean getters can indeed be invoked more than once in bean's life. Bean getters are purely intented to return data, not to load data. You normally use the bean class constructor, or init block, or lazy loading, or action(event) methods for this.
1) So my questions are, why is this called twice?
2) How do I stop it being called twice?Carefully read those articles.
[http://balusc.blogspot.com/2006/09/debug-jsf-lifecycle.html]
[http://balusc.blogspot.com/2006/06/using-datatables.html]
That said, the name of your ' PooledConnectionHelper' class scares me... At that stage in the code you normally really shouldn't worry about if it is a pooled connection or a normal connection. This is honestly a smell.