Each ValidField is configured with a validator which checks the correctness of the user's input and performs the input text to java Object translations. The Form tracks the state of all its ValidFields using a validation delegate. Using the validation delegate you can determine whether all the form's fields are valid and inform the user of any validation errors.

There are number of pluggable validators you can assign to a ValidField including:

• DateValidator - validates date strings and allows a minimum and maximum date range to be set
• EmailValidator - validates email strings and allows a minimum and maximum length to be set
• NumberValidator - validates number strings and allows a minimum and maximum values to be set
• PatternValidator - validates text for a specified pattern
• StringValidator - validates string values and allows a minimum length to be set

<bean name="emailValidator" class="org.apache.tapestry.valid.EmailValidator">
    <set-property name="clientScriptingEnabled" expression="true"/>
    <set-property name="minimumLength" expression="8"/>
    <set-property name="required" expression="true"/>
</bean>

Note if a form includes a "Cancel" style submit button, the cancel button will need to set the form's onsubmit event handler to null, so that the JavaScript field validation is not invoked when the form is submitted. For example:

  <input jwcid="@Submit" listener="ognl:listeners.okSubmit" type="Submit" value="  OK  "/>
  <input jwcid="@Submit" listener="ognl:listeners.cancelSubmit" type="Submit" value="Cancel" onclick="form.onsubmit = null;"/>

Body: removed
Informal parameters:allowed
Reserved parameters: "name", "type", "value"

The ValidField is used in this example to provide an auction bidding page. A custom ValidationDelegate is used to render the invalid fiels as yellow. A custom ShowError component is also used to display the first error message if any fields have errors.

For a more extensive example see the Tapestry Workbench. The Fields example in the Workbench also illustrates how to use the FieldLabel component to high light invalid fields.

<form jwcid="@Form" delegate="ognl:beans.delegate">
<table class="examples" cellpadding="2">
<tr>
 <td colspan="2"><span class="title">Regal Auctions Bid Page</span></td>
</tr>
<tr>
 <td colspan="2"><hr></td>
</tr>
<tr>
 <td colspan="2"><span jwcid="@ShowError" delegate="ognl:beans.delegate"/></td>
</tr>
<tr>
 <td><span jwcid="@FieldLabel" field="ognl:components.lotNoField">Lot Number</span></td><td><input jwcid="lotNoField" type="text" size="4" maxlength="4"/></td>
</tr>
<tr>
 <td><span jwcid="@FieldLabel" field="ognl:components.bidAmountField">Bid Amount</span></td><td><input jwcid="bidAmountField" type="text" size="7" maxlength="7"/></td>
</tr>
<tr>
 <td><span jwcid="@FieldLabel" field="ognl:components.fullNameField">Full Name</span></td><td><input jwcid="fullNameField" type="text" size="25" maxlength="30"/></td>
</tr>
<tr>
 <td><span jwcid="@FieldLabel" field="ognl:components.emailField">Email</span></td><td><input jwcid="emailField" type="text" size="25" maxlength="30"/></td>
</tr>
<tr>
 <td><span jwcid="@FieldLabel" field="ognl:components.telephoneField">Telephone</span></td><td><input jwcid="telephoneField" type="text" size="25" maxlength="30"/></td>
</tr>
<tr>
 <td colspan="2" align="right">
  <input jwcid="@Submit" listener="ognl:listeners.okSubmit"  type="Submit" value="   OK   "/>
  <input jwcid="@Submit" listener="ognl:listeners.cancelSubmit"onclick="form.onsubmit = null;"/>
 </td>
</tr>
</table>
</form>


<property-specification name="lotBid" type="com.mycorp.LotBid" persistent="yes" initial-value="new com.mycorp.LotBid()"/>
<property-specification name="actionDetails" type="com.mycorp.ActionDetails" persistent="yes"/>

<bean name="delegate" class="com.mycorp.FormValidationDelegate"/>

<bean name="lotNoValidator" class="org.apache.tapestry.valid.NumberValidator">
    <set-property name="required" expression="true"/>
    <set-property name="minimum" expression="1"/>
    <set-property name="maximum" expression="auctionDetails.numberLots"/>
    <set-property name="valueType">"int"</set-property>
</bean>

<bean name="bidAmountValidator" class="org.apache.tapestry.valid.NumberValidator">
    <set-property name="required" expression="true"/>
    <set-property name="minimum" expression="auctionDetails.minBid"/>
    <set-property name="maximum" expression="auctionDetails.maxBid"/>
    <set-property name="valueType">"float"</set-property>    
</bean>

<bean name="fullNameValidator" class="org.apache.tapestry.valid.StringValidator">
    <set-property name="required" expression="true"/>
    <set-property name="minimumLength" expression="3"/>
</bean>

<bean name="emailValidator" class="org.apache.tapestry.valid.StringValidator">
    <set-property name="required" expression="true"/>
    <set-property name="minimumLength" expression="12"/>
</bean>

<bean name="telephoneValidator" class="org.apache.tapestry.valid.StringValidator">
    <set-property name="required" expression="true"/>
    <set-property name="minimumLength" expression="11"/>
</bean>

<component id="lotNoField" type="ValidField">
    <binding name="value" expression="lotBid.lotNo"/>
    <binding name="validator" expression="beans.lotNoValidator"/>
    <static-binding name="displayName" value="Lot Number"/>
</component>

<component id="bidAmountField" type="ValidField">
    <binding name="value" expression="lotBid.bidAmount"/>
    <binding name="validator" expression="beans.bidAmountNoValidator"/>
    <static-binding name="displayName" value="Bid Amount"/>
</component>

<component id="fullNameField" type="ValidField">
    <binding name="value" expression="lotBid.bidderName"/>
    <binding name="validator" expression="beans.fullNameValidator"/>
    <static-binding name="displayName" value="Full Name"/>
</component>

<component id="emailField" type="ValidField">
    <binding name="value" expression="lotBid.bidderEmail"/>
    <binding name="validator" expression="beans.emailValidator"/>
    <static-binding name="displayName" value="Email"/>
</component>

<component id="telephoneField" type="ValidField">
    <binding name="value" expression="lotBid.bidderTelephone"/>
    <binding name="validator" expression="beans.telephoneValidator"/>
    <static-binding name="displayName" value="Telephone"/>;
</component>


public abstract class LotBidPage extends BasePage {
    public abstract LotBid getLotBid();

    public abstract void setLotBid(LotBid value);
    public asbtract AuctionDetails getAuctionDetails();

    public abstract void setAuctionDetails(AuctionDetails value);

    public void okSubmit(IRequestCycle cycle) {
        ValidationDelegate delegate = (ValidationDelegate) 
            getBeans().getBean("delegate");

        // If no errors process the bid, otherwise stay on this page and 
        // let the fields show their errors.
        if (!delegate.getHasErrors())
            // Save the lot bid to the database.
            ..
            
            // Go to the confirmation page.
            cycle.activate("BidConfirmPage");
        }
    }
    
    public void cancelSubmit(IRequestCycle cycle) {
        cycle.activate("AuctionListPage");
    }
}

public class LotBid implements Serializable {
    private int lotNo;
    private float bidAmount;
    private String bidderName;
    private String bidderEmail;
    private String bidderTelephone;

    public int getLotNo() { return lotNo; }
    
    public void setLotNo(int value) {
        lotNo = value;
    }

    public float getBidAmount() { return bidAmount; }
    
    public void setBidAmount(float value) {
        bidAmount = value;
    }
                  
    public float getBidderName() { return bidderName; }
    
    public void setBidderName(String value) {
        bidderName = value;
    }
    
    public float getBidderEmail() { return bidderEmail; }
    
    public void setBidderEmail(String value) {
        bidderEmail = value;
    }
    
    public float getBidderTelephone() { return bidderTelephone; }
    
    public void setBidderTelephone(String value) {
        bidderTelephone = value;
    }    
}

public class AuctionDetails implements Serializable {
    private int numberLots;
    private float minBid;
    private float maxBid;
    
    public AuctionDetails(int numberLots, float minBid, float maxBid) {
        this.numberLots = numberLots;
        this.minBid = minBid;
        this.maxBid = maxBid;
    }
    
    public int getNumberLots() { return numberLots; }
    
    public float getMinBid() { return minBid; }

    public float getMaxBid() { return maxBid; }    
}