Collections (ArrayList), web flow forms, and data binding

[John.Turner]

G'day All,

I have a requirement to retrieve a list of objects from the database, display them in a 'multi-record' form so that they can be edited, and then save the modified records back to the database. I have set up a web flow to retrieve the records from the database, and then present them to the user in a form. I am having problems binding the data to the form. I am also not sure how to access the data after it has been posted.

I have read a large number of threads on this forum and experimented with different syntax in the JSP file but still cannot render a JSP containing a form with the data bound.

I am using Spring v2.5 and Spring Web Flow v1.0.5.

Spring beans config:

    <bean id="viewResolver"
          class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" 
                  value="org.springframework.web.servlet.view.tiles.TilesJstlView" />
    </bean>
    
    <bean id="urlMapping"
          class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <prop key="flow.htm">flowController</prop>
            </props>
        </property>
    </bean>
    
    <bean id="tilesConfigurer" 
          class="org.springframework.web.servlet.view.tiles.TilesConfigurer">
        <property name="definitions">
            <list>
                <value>/WEB-INF/foo-tiles.xml</value>
            </list>
        </property>
    </bean>
    
    <bean id="flowController" 
          class="org.springframework.webflow.executor.mvc.FlowController">
        <property name="flowExecutor" ref="flowExecutor" />
    </bean>
    
    <flow:executor id="flowExecutor" registry-ref="flowRegistry" />
    
    <flow:registry id="flowRegistry">
        <flow:location path="/WEB-INF/flow/**/*-flow.xml" />
    </flow:registry>
    
    <bean id="retrieveRelationshipTypesAction"
          class="foo.action.RetrieveRelationshipTypesAction">
    </bean>
    
    <bean id="saveRelationshipTypeAction"
          class="foo.action.SaveRelationshipTypeAction"/>
    
    <bean id="relationshipTypeFormAction"
          class="foo.form.RelationshipTypeFormAction">
        <property name="formObjectName" value="rtList"/>
        <property name="formObjectScope" value="REQUEST" />
        <property name="formObjectClass" value="java.util.ArrayList"/>
    </bean>

Web flow definition:

    <var name="relationshipTypes" class="java.util.ArrayList" scope="flow" />
    
    <start-state idref="retrieveRelationshipTypes" />
    
    <action-state id="retrieveRelationshipTypes">
        <action bean="retrieveRelationshipTypesAction" />
        <transition on="success" to="showRelationshipTypes" />
    </action-state>
    
    <view-state id="showRelationshipTypes" view="relationshipType.page" >
        <render-actions>
            <action bean="relationshipTypeFormAction" method="setupForm"/>
            <action bean="relationshipTypeFormAction" method="populateList"/>
        </render-actions>
        <transition on="select" to="saveRelationshipType" >
            <action bean="relationshipTypeFormAction" method="bind" />
            <evaluate-action expression="requestScope.pgOfRelTypes">
                <evaluation-result name="flowScope.relationshipTypes" />
            </evaluate-action>
        </transition>
    </view-state>
    
    <action-state id="saveRelationshipType">
        <action bean="saveRelationshipTypeAction" />
        <transition on="success" to="showRelationshipTypes" />
    </action-state>

My action form class is:

package foo.form;

import...

public class RelationshipTypeFormAction extends FormAction {

    private static Logger log = Logger.getLogger(RelationshipTypeFormAction.class);

    public Event populateList(RequestContext context) throws Exception {
        log.debug("populateList: in");
        ArrayList<ItemRelationshipType> relationshipTypes = (ArrayList<ItemRelationshipType>) context.getFlowScope().get("relationshipTypes");
        ArrayList<ItemRelationshipType> rtList = (ArrayList<ItemRelationshipType>) getFormObject(context);
        rtList.clear();
        rtList.addAll(relationshipTypes);
        log.debug("populateList: out");
        return success();
    }
}

JSP page (I'm using tiles):

<jsp:directive.include file="/WEB-INF/page/tags.jsp" />

<h3>Relationship Types</h3>

<form:form action="flow.htm" commandName="rtList">
    <input type="hidden" name="_flowExecutionKey" value="${flowExecutionKey}">
    <input type="hidden" name="targetAction" value="error">
    <table width="80%">
        <tr>
            <td>
                ID
            </td>
            <td>
                Name
            </td>
            <td>
                Description
            </td>
        </tr>
        
        <c:forEach items="${rtList}" var="rt" varStatus="loop">
            <tr>
                <td>
                    <%-- <c:out value="${rt.itemRelationshipTypeId}" /> --%>
                    <form:input path="${rtList}[${loop.index}].itemRelationshipTypeId" />
                </td>
                <td>
                    <%-- <c:out value="${rt.name}" /> --%>
                    <form:input path="${rtList}[${loop.index}].name" />
                </td>
                <td>
                    <%-- <c:out value="${rt.description}" /> --%>
                    <form:input path="${rtList}[${loop.index}].description" />
                </td>
            </tr>
        </c:forEach>
        
    </table>
    <p>
        <input type="submit" name="_eventId_cancel" value="Cancel"/>
        <input type="submit" name="_eventId_save" value="Save"/>
    </p>
</form:form>

When this JSP is called I get this error:

17:14:11,225 [[ACTIVE] ExecuteThread: '0' for queue: 'weblogic.kernel.Default (self-tuning)'] ERROR org.springframework.web.servlet.tags.form.InputTag - Invalid property '[foo.model.ItemRelationshipType@79b022, foo.model.ItemRelationshipType@79b00e, foo.model.ItemRelationshipType@79affa][0]' of bean class [java.util.ArrayList]: Bean property '[foo.model.ItemRelationshipType@79b022, foo.model.ItemRelationshipType@79b00e, foo.model.ItemRelationshipType@79affa][0]' is not readable or has an invalid getter method: Does the return type of the getter match the parameter type of the setter?
org.springframework.beans.NotReadablePropertyException: Invalid property '[foo.model.ItemRelationshipType@79b022, foo.model.ItemRelationshipType@79b00e, foo.model.ItemRelationshipType@79affa][0]' of bean class [java.util.ArrayList]: Bean property '[foo.model.ItemRelationshipType@79b022, foo.model.ItemRelationshipType@79b00e, foo.model.ItemRelationshipType@79affa][0]' is not readable or has an invalid getter method: Does the return type of the getter match the parameter type of the setter?
	at org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:544)
	at org.springframework.beans.BeanWrapperImpl.getNestedBeanWrapper(BeanWrapperImpl.java:451)
	at org.springframework.beans.BeanWrapperImpl.getBeanWrapperForPropertyPath(BeanWrapperImpl.java:428)
	...

Can anyone tell me what the correct syntax is for binding to a list? I've tried several variations on what I've presented here but with no success.

Thanks, John

[Marten Deinum]

You cannot use a List as a formBackingObject. You can use an object containing a List. The samples shipped with Spring provide a working sample of that.

[John.Turner]

Marten, Thanks for your suggestion. I now have the binding working OK. Regards, John

For future reference the syntax for binding in the JSP is:

<jsp:directive.include file="/WEB-INF/page/tags.jsp" />

<h3>Relationship Types</h3>

<form:form action="flow.htm" commandName="relationshipTypeForm">
    <input type="hidden" name="_flowExecutionKey" value="${flowExecutionKey}">
    <input type="hidden" name="targetAction" value="error">
    <table width="80%">
        <tr>
            <td>
                ID
            </td>
            <td>
                Name
            </td>
            <td>
                Description
            </td>
        </tr>
        
        <c:forEach items="${relationshipTypeForm.rtList}" var="rt" varStatus="loop">
            <tr>
                <td>
                    <%-- <c:out value="${rt.itemRelationshipTypeId}" /> --%>
                    <form:input path="rtList[${loop.index}].itemRelationshipTypeId" />
                </td>
                <td>
                    <%-- <c:out value="${rt.name}" /> --%>
                    <form:input path="rtList[${loop.index}].name" />
                </td>
                <td>
                    <%-- <c:out value="${rt.description}" /> --%>
                    <form:input path="rtList[${loop.index}].description" />
                </td>
            </tr>
        </c:forEach>
        
    </table>
    <p>
        <input type="submit" name="_eventId_cancel" value="Cancel"/>
        <input type="submit" name="_eventId_save" value="Save"/>
    </p>
</form:form>

[geoffreyeaster]

How are you applying validation to this? How do you refer to the indexed list in your validator?

[Shachi Rai]

You cannot use a List as a formBackingObject. You can use an object containing a List. The samples shipped with Spring provide a working sample of that.

Could you please provide the URL for the samples you have referred in your comment