Using a drop-down list in a model driven action class in Struts2

Question

I'm populating an <s:select> from database. The action class is model-driven.

@Namespace("/admin_side")
@ResultPath("/WEB-INF/content")
@ParentPackage(value="struts-default")
public final class TestAction extends ActionSupport implements Serializable, ValidationAware, Preparable, ModelDriven<Transporter>
{
    @Autowired
    private final transient SharableService sharableService=null;
    private static final long serialVersionUID = 1L;

    private Transporter transporter; //Getter and setter
    private Long transporterId; //Getter and setter.
    private List<Transporter> transporters; //Getter only.

    @Action(value = "Test",
            results = {
                @Result(name=ActionSupport.SUCCESS, location="Test.jsp"),
                @Result(name = ActionSupport.INPUT, location = "Test.jsp")},
            interceptorRefs={@InterceptorRef(value="defaultStack", params={"validation.validateAnnotatedMethodOnly", "true", "validation.excludeMethods", "load"})})
    public String load() throws Exception
    {
        return ActionSupport.SUCCESS;
    }

    @Validations(
            requiredFields={@RequiredFieldValidator(fieldName="transporterId", type= ValidatorType.FIELD, key = "transporter.required")})
    @Action(value = "testInsert",
        results = {
            @Result(name=ActionSupport.SUCCESS, location="Test.jsp", params={"namespace", "/admin_side", "actionName", "Test"}),
            @Result(name = ActionSupport.INPUT, location = "Test.jsp")},
        interceptorRefs={@InterceptorRef(value="defaultStack", params={"validation.validateAnnotatedMethodOnly", "true"})})
    public String insert() {
        System.out.println("Selected item in the drop box : "+transporterId);
        return ActionSupport.SUCCESS;
    }

    @Override
    public void prepare() throws Exception {
        transporters=sharableService.getTransporterList();
    }

    @Override
    public Transporter getModel() {
        return transporter;
    }
}

and the following is <s:select> :

<s:select id="transporterId" 
          name="transporterId" 
          list="transporters" 
          value="transporterId" 
          listKey="transporterId" 
          listValue="transporterName" 
          headerKey="" headerValue="Select" 
          listTitle="transporterName"/>

This works perfectly.

---

I need this <s:select> in another action class which implements ModelDriven<ZoneTable>.

The table structure is simple, transporter->zone_table->country->state->city. There exists a one-to-many relationship between these tables.

How can we have a model driven action class implementing ModelDrven<ZoneTable> in which Transporter can be mapped to <s:select>, something like?

@Namespace("/admin_side")
@ResultPath("/WEB-INF/content")
@ParentPackage(value="struts-default")
public final class ZoneAction extends ActionSupport implements Serializable, ValidationAware, Preparable, ModelDriven<ZoneTable>
{
    @Autowired
    private final transient ZoneService zoneService=null;
    @Autowired
    private final transient SharableService sharableService=null;

    private ZoneTable entity=new ZoneTable(); //Getter and setter.
    private Long transporterId; //Getter and setter.
    private List<Transporter> transporters; //Getter only.

    @Override
    public ZoneTable getModel() {
        return entity;
    }

    @Override
    public void prepare() throws Exception {
        transporters=sharableService.getTransporterList();
    }
}

Doing like this doesn't work. It doesn't set the value of transporterId upon submission, since the action class is implementing ModelDriven<ZoneTable> and not ModelDriven<Transporter> like the first case.

Is this possible using the model driven approach?

---

EDIT:

ZoneTable.java

public class ZoneTable implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "zone_id", nullable = false)
    private Long zoneId;
    @Column(name = "zone_name", length = 45)
    private String zoneName;
    @JoinColumn(name = "transporter_id", referencedColumnName = "transporter_id")
    @ManyToOne(fetch = FetchType.LAZY)
    private Transporter transporterId;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "zoneTable", fetch = FetchType.LAZY)
    private Set<ZoneCharge> zoneChargeSet;
    @OneToMany(mappedBy = "zoneId", fetch = FetchType.LAZY)
    private Set<Country> countrySet;

    //Getters and setters + constructors.
}

Zone.jsp

<s:form namespace="/admin_side" action="Zone" validate="true" id="dataForm" name="dataForm" cssClass="search_form general_form">

    <s:label key="label.zone.name" for="zone"/>
    <s:textfield id="zoneName" name="zoneName" cssClass="validate[required, maxSize[45], minSize[2]] text-input text"/>
    <s:fielderror fieldName="zoneName"/>

    <s:label key="label.transporter.name" for="transporterId"/>
    <s:select id="transporterId" name="transporterId" list="transporters" value="transporterId" listKey="transporterId" listValue="transporterName" headerKey="" headerValue="Select" listTitle="transporterName"/>
    <s:fielderror fieldName="transporterId"/>

    <s:text name="label.submit"/>
    <s:submit id="btnSubmit" name="btnSubmit" value="Submit" action="AddZone"/>

</s:form>

Since this post has already a lot of code, I'm not posting the action class ZoneAction.java here. In case, it is needed, it is available here.

Answer 1

You need a converter to convert transporterId to Transporter Object. It goes like this:

package com.converter;

public class TransporterConverter extends StrutsTypeConverter {

    @Override
    public Object convertFromString(Map map, String[] strings, Class type) {

        String value = strings[0]; // The value of transporterId submitted from the jsp

        if (value != null && value.length() > 0) {
            try {
                Long longVal = Long.valueOf(value);
                //Integer intVal = Integer.valueOf(value);
                if (type == Transporter.class) {
                    Transporter data = find_transporter_from_the_back_by_transporter_id_using_longVal;
                    return data;
                }
            } catch (Exception ex) {}
        }
        return null;
    }

    @Override
    public String convertToString(Map map, Object o) {

        if ((o instanceof Transporter)) {
            Transporter data = (Transporter) o;
            //return the id of the Transporter Object
        }
        return null;
    }
}

The next thing to do is to map this class in a file called xwork-conversion.properties. This file must reside in your classpath i.e. in classes directory. Enter the following entries in xwork-conversion.properties

package_of_transporter_class.Transporter=com.converter.TransporterConverter

I have not tested it, but I think it should work.

If you need more information on how type converters work, follow this url.