Storing Data in a Page

Sometimes there are fields in a page that you want the page to store for use next time you access the page.
To do this, annotate those fields with @Persist.

In this example we use @Persist on a field called count. We increment count every time the page is rendered.
If you revisit this page or reload it, you will see that count has been remembered and incremented.
The number of times you have visited this page during this session: 1
The default strategy for @Persist is "session", which means store the field's value server-side in your web session. Alternative strategies for @Persist include "flash" and "client" - see Persistent Page Data.

To remove a session-persisted field from the session, set it to null, or call ComponentResources' discardPersistentFieldChanges() method as demonstrated by this link:
Remove count from the Session and go Home.
To see what's currently stored in your session, see the Display Session Contents example.

Caution

You can add your own persistence strategy: see How To Use Persistent Field Strategy.

References: Persistent Page Data, @Persist, PersistenceConstants, Clustering Issues, How To Use Persistent Field Strategy.

Home


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- We need a doctype to allow us to use special characters like &nbsp; 
     We use a "strict" DTD to make IE follow the alignment rules. -->
     
<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_4.xsd">
<body class="container">
    <h3>Storing Data in a Page</h3>
    
    Sometimes there are fields in a page that you want the page to store for use next time you access the page.<br/>
    To do this, annotate those fields with <code>@Persist</code>.<br/><br/>
    
    In this example we use @Persist on a field called <em>count</em>. We increment <em>count</em> every time the page is rendered.<br/>
    If you revisit this page or reload it, you will see that <em>count</em> has been remembered and incremented.
    
    <div class="eg">
        The number of times you have visited this page during this session: <strong>${count}</strong>
    </div>
    
    The default <em>strategy</em> for @Persist is "session", which means store the field's value server-side in your web session. 
    Alternative strategies for @Persist include "flash" and "client" - see 
    <a href="http://tapestry.apache.org/persistent-page-data.html">Persistent Page Data</a>. <br/><br/>
    
    To remove a session-persisted field from the session, set it to null, or call ComponentResources' 
    <code>discardPersistentFieldChanges()</code> method as demonstrated by this link:
    
    <div class="eg">
        <a t:type="eventlink" t:event="clear" href="#">Remove count from the Session and go Home</a>.
    </div>
     
    To see what's currently stored in your session, see the Display Session Contents example.<br/><br/>
    
    <p><strong>Caution</strong></p>
    <ul>
        <li>The "session" strategy is risky because many browsers share the same session across windows and tabs.
            The danger is that the field will be overwritten if the user opens a new window or tab and visits the same page. 
            We address this issue in the Wizard examples by creating a "conversation".</li>
        <li>"Session" persistence also has an impact on clustered servers.  Howard discusses this in 
            <a href="http://thread.gmane.org/gmane.comp.java.tapestry.user/65410/focus=65426">Tapestry App Replication</a> 
            (note that <em>@ApplicationState</em> is the old name for <em>@SessionState</em>)
            and the documentation discusses it in 
            <a href="http://tapestry.apache.org/persistent-page-data.html#PersistentPageData-ClusteringIssues">Clustering Issues</a>.</li>
    </ul>

    You can add your own persistence strategy: see
    <a href="http://wiki.apache.org/tapestry/Tapestry5HowToUsePersistentFieldStrategy">How To Use Persistent Field Strategy</a>.<br/><br/> 
    
    References: <a href="http://tapestry.apache.org/persistent-page-data.html">Persistent Page Data</a>, 
    <a href="http://tapestry.apache.org/5.4/apidocs/org/apache/tapestry5/annotations/Persist.html">@Persist</a>, 
    <a href="http://tapestry.apache.org/5.4/apidocs/org/apache/tapestry5/PersistenceConstants.html">PersistenceConstants</a>, 
    <a href="http://tapestry.apache.org/persistent-page-data.html#PersistentPageData-ClusteringIssues">Clustering Issues</a>, 
    <a href="http://wiki.apache.org/tapestry/Tapestry5HowToUsePersistentFieldStrategy">How To Use Persistent Field Strategy</a>.<br/><br/>
    
    <t:pagelink page="Index">Home</t:pagelink><br/><br/>

    <t:tabgroup>
        <t:sourcecodetab src="/web/src/main/java/jumpstart/web/pages/examples/state/StoringDataInAPage.tml"/>
        <t:sourcecodetab src="/web/src/main/java/jumpstart/web/pages/examples/state/StoringDataInAPage.java"/>
        <t:sourcecodetab src="/web/src/main/resources/META-INF/assets/css/examples/olive.css"/>
    </t:tabgroup>
</body>
</html>



package jumpstart.web.pages.examples.state;

import jumpstart.web.pages.Index;

import org.apache.tapestry5.ComponentResources;
import org.apache.tapestry5.annotations.Import;
import org.apache.tapestry5.annotations.Persist;
import org.apache.tapestry5.annotations.Property;
import org.apache.tapestry5.ioc.annotations.Inject;

@Import(stylesheet="css/examples/olive.css")
public class StoringDataInAPage {

    // Screen fields

    @Property
    @Persist
    private int count;

    // Generally useful bits and pieces

    @Inject
    private ComponentResources componentResources;

    // The code
    
    void setupRender() {
        count++;
    }

    Object onClear() {
        componentResources.discardPersistentFieldChanges();
        return Index.class;
    }
}



.eg {
                margin: 20px 0;
                padding: 14px;
                color: olive;
                border: 1px solid #ddd;
                border-radius: 6px;
                -webkit-border-radius: 6px;
                -mox-border-radius: 6px;
}