How can I omit properties from the view state?

Question

The documentation says that using the transient keyword on properties will keep them out of the view state, but my testing seems to show otherwise. How can I exclude this property from the view state?

Example of smallest view state (0.86kb internal):

// ViewStateProblems.cls
public class ViewStateProblems {
}

// ViewStateProblems.page
<apex:page controller="ViewStateProblems">
    <apex:form ></apex:form> <!-- remove the form and view state goes away -->
</apex:page>

Example showing a table of records with no view state (0kb):

// ViewStateProblems.cls
public class ViewStateProblems {
    public List<Case> getCases(){
        return [select CaseNumber, OwnerId, ContactId from Case limit 1000];
    }
}

// ViewStateProblems.page
<apex:page controller="ViewStateProblems">
    <apex:pageBlock >
        <apex:pageBlockTable value="{!cases}" var="c">
            <apex:column value="{!c.CaseNumber}"/>
            <apex:column value="{!c.OwnerId}"/>
            <apex:column value="{!c.ContactId}"/>
        </apex:pageBlockTable>
    </apex:pageBlock>
</apex:page>

Turning on view state by just adding a form to the page. Note, my cases object is not in the form tags (internal view state of 26.02):

// ViewStateProblems.cls
public class ViewStateProblems {
    public List<Case> getCases(){
        return [select CaseNumber, OwnerId, ContactId from Case limit 1000];
    }
}

// ViewStateProblems.page
<apex:page controller="ViewStateProblems">
    <apex:pageBlock >
        <apex:pageBlockTable value="{!cases}" var="c">
            <apex:column value="{!c.CaseNumber}"/>
            <apex:column value="{!c.OwnerId}"/>
            <apex:column value="{!c.ContactId}"/>
        </apex:pageBlockTable>
    </apex:pageBlock>
    <apex:form> maybe create new case here </apex:form>
</apex:page>

Picture of view state (I don't yet sufficient karma to upload photos): http://cl.ly/image/1N183P2C3D3W

Here I make a version using the transient keyword on the cases property but it has no effect on the view state size (internal view state of 26.02):

// ViewStateProblems.cls
public class ViewStateProblems {
    public transient List<Case> cases {get; private set;} {
        cases = [select CaseNumber, OwnerId, ContactId from Case limit 1000]; 
    }
}

// ViewStateProblems.page
<apex:page controller="ViewStateProblems">
    <apex:pageBlock >
        <apex:pageBlockTable value="{!cases}" var="c">
            <apex:column value="{!c.CaseNumber}"/>
            <apex:column value="{!c.OwnerId}"/>
            <apex:column value="{!c.ContactId}"/>
        </apex:pageBlockTable>
    </apex:pageBlock>
    <apex:form> maybe create new case here </apex:form>
</apex:page>

Shouldn't that example using the transient keywork have had the same internal view state size as the first form example of only 0.86kb? If not, how can I stop the cases property from being sent in view state?

Answer 1

The Salesforce documentation states that using transient keyword will reduce the view state, but it also states that it stores some of VF data for housekeeping. To reduce the view state size please try the below code.

<apex:pageBlock >
        <table cellspacing="0" cellpadding="0" border="0" id="searchResults" class="list">
             <thead class="rich-table-thead">
                 <tr class="headerRow">
                     <th>Case Number</th>
                     <th>Case Owner</th>
                     <th>Contact Name</th>
                 </tr>
             </thead>
             <tbody>
                 <apex:repeat value="{!cases}" var="c">
                     <tr onfocus="if (window.hiOn){hiOn(this);}" onblur="if (window.hiOff){hiOff(this);}" onmouseout="if (window.hiOff){hiOff(this);} " onmouseover="if (window.hiOn){hiOn(this);} " class="dataRow even  first">
                         <td class="dataCell">{!c.CaseNumber}</td>
                         <td class="dataCell">{!c.OwnerId}</td>
                         <td class="dataCell">{!c.ContactId}</td>
                     </tr>
                 </apex:repeat>
             </tbody>
         </table>
     </apex:pageBlock> 
   <apex:form > maybe create new case here </apex:form>  

Here we are replacing pageblocktable with a html table. In my observation pageblocktable seems to consume a big part of Internal view state. Using the above code will reduce around 45-48% view state.

Answer 2

The viewstate contains all the information that needs to be moved from the controller back to the page. Using transient on a property that is used in your page is of no help as you want that information and so the system sends it down as it should do so you can see it.

If you declare a private member in your controller and initialised it with a huge string you'll see your view state size increase. If you then add transient you'll see it go down again as that string value will not longer be passed back and forth on each request.

I don't know for sure but I suspect that in the setup you've described here, although your value is in the view state so the records can be displayed on the page, I doubt any values are sent back to the system in the next request.

Long story short, values for properties you need on the page will always be in the viewstate. The transient keyword is to indicate to the system which information can be discarded when a request is completed because you won't need it in the next one.

Answer 3

The docs contain a nicely informative summary of the ingredients of the view state:

The data in the view state should be sufficient to recreate the state of the page when the postback is received. To do this, it stores the following data:

All non-transient data members in the associated controller (either standard or custom) and the controller extensions.

Objects that are reachable from a non-transient data member in a controller or controller extension.

The component tree for that page, which represents the page's component structure and the associated state, which are the values applied to those components.

A small amount of data for Visualforce to do housekeeping.

View state data is encrypted and cannot be viewed with tools like Firebug. The view state inspector described below lets you look at the contents of view state.

So due to #3 above, you can't ever prevent values that are applied to components from being sent in view state, because they are required by the design of Visualforce views.

Answer 4

The following code will remove the setter and thus remove the cases property from the viewstate.

// ViewStateProblems.cls
public class ViewStateProblems {
    public List<Case> getcases() {
        return [select CaseNumber, OwnerId, ContactId from Case limit 1000]; 
    }
}