Struts2: Updating the values of a “List Of Objects

Question

There is an object ObjectA which has a list of ObjectB. There is a TreeMap inside the ObjectB. This TreeMap has a String as key and a List of another object ObjectC as value. This TreeMap and the list inside has been displayed on the jsp using the s:iterator and s:textfield and it is being displayed correctly. i.e. the "values" inside the s:textfield are correct. Now, the problem arises when the textfield is modified. How do we capture the modified values inside ObjectC in the action class? With the code given here, the key ("Key1") comes in the action but the value is null.

Java Code

public class ObjectA implements Serializable {
private Integer attr1;
private List<ObjectB> objB;
//...getters and setters....
public class ObjectB implements Serializable {
private Integer attr11;
private TreeMap<String,List<ObjectC>> allPlainFields;
// ...getters and setters....
public class ObjectC implements Serializable {
private Integer attr111;
public String attr112;
// ...getters and setters....

JSP Code

<s:iterator value="objA.objB" var="currentObjB" status="currentGroupStatus">

  <s:iterator value="#currentObjB.allPlainFields" var="parentMap" status="headerStatus">
     <s:iterator value="#parentMap.value" var="fieldList" status="fieldStatus">

       <s:textfield  name="objA.objB[%{#currentGroupStatus.index}].allPlainFields['%{#parentMap.key}'][%{#fieldStatus.index}].attr112"/>


</s:iterator>                       

 </s:iterator> 

HTML rendered: <input type="text" id="review-act1_objA_objB_0__allPlainFields_'Key1'__6__attr112" value="Correct Value" name="objA.objB[0].allPlainFields['Key1'][0].attr112">

The object structure in the "VAriables" view of eclipse shows:

objA    Object A  (id=955)  
objB    ArrayList<E>  (id=966)  
    elementData Object[10]  (id=967)    
        [0] ObjectB  (id=968)   
            allPlainFields  TreeMap<K,V>  (id=972)  
                comparator  null    
                descendingMap   null    
                entrySet    TreeMap$EntrySet  (id=979)  
                keySet  null    
                modCount    1   
                navigableKeySet null    
                root    TreeMap$Entry<K,V>  (id=980)    
                size    1   
                values  null    

        [1] ObjectB  (id=969)   
        [2] ObjectB  (id=970)   
        [3] ObjectB  (id=971)   
        [4] null    
        [5] null    
        [6] null    
        [7] null    
        [8] null    
        [9] null    
    modCount    4   
    size    4   

****In the Eclipse "Variables" view, the value for allPlainFields is**:** {Key1=}

EDIT(27-Feb-2013):

Tried this but didn't work. The values appear on jsp but when submitted, they don't come in action:

In Action class:

private TreeMap<String,ObjectCList> testTreeMap = new TreeMap<String,ObjectCList>();
//get,set and setting two keys in map "mykey1" and "mykey2"

In ObjectCList class:

private ArrayList<ObjectC> paramMdlList;
 //default constructor, get, set

In JSP:

<s:form id="test-map" method="post">
<s:iterator value="testTreeMap" var="pMap" status="hStatus">
     <li><label><s:property value="%{#pMap.key}" /></label> 
        <s:iterator value="%{#pMap.value.paramMdlList}" var="pList" status="innerStatus">
            <s:textfield name="testTreeMap['%{#pMap.key}'].paramMdlList[%{#innerStatus.index}].attr111"/>
            <s:textfield name="testTreeMap['%{#pMap.key}'].paramMdlList[%{#innerStatus.index}].attr112"/> 

        </s:iterator>


    </li>

</s:iterator>
<s:submit value=" " type='button' id="btnh1" action="saveTreeMap">
            <span>Save TreeMap</span>
</s:submit>
</s:form>

When the form is submitted, updateTreeMap method of the action is called. The map is printed as mentioned here :

public String updateTreeMap(){

    for (Map.Entry<String, ObjectCList> entry : testTreeMap.entrySet())
    {
        System.out.println(entry.getKey() + "/" + entry.getValue());
    }

    return SUCCESS;

}

What is "printed" : mykey1/ mykey2/ i.e. null values

The screen below shows values coming in jsp

Answer 1

I've become curious and did other experiments.

I found out that neither Lists inside Lists, nor Maps inside Maps (and all the interpolations), declared as interface (List, Map), or as their implementations (ArrayList, HashMap, TreeMap) are correctly handled by the XWork Converter.

All the test cases have failed.

Maybe it's my fault, if so we really need some OGNL Experts here, because in the whole web there's nothing talking about this.

Then i tried what I was pretty sure that would have worked: encapsulating this informations in custom objects, in pure OOP way.

And it worked :)

Instead of

private ArrayList<ArrayList<String>> outerObjects;

you can use in your Action

private ArrayList<OuterObject> outerObjects; 

/* GETTERS AND SETTERS */
public ArrayList<OuterObject> getOuterObjects() {
    return outerObjects;
}
public void setOuterObjects(ArrayList<OuterObject> outerObjects) {
    this.outerObjects = outerObjects;
}

the OuterObject definition:

/* ELSEWHERE IN YOUR PROJECT... */
public class OuterObject{
    private ArrayList<InnerObject> innerObjects;

    /* GETTERS AND SETTERS */
    public ArrayList<InnerObject> getInnerObjects() {
        return innerObjects;
    }
    public void setInnerObjects(ArrayList<InnerObject> innerObjects) {
        this.innerObjects = innerObjects;
    }       
}

the InnerObject definition:

public class InnerObject{
    String innerField;

    /* GETTERS AND SETTERS */       
    public String getInnerField() {         
        return innerField;
    }
    public void setInnerField(String innerField) {
        this.innerField = innerField;
    }

}

the optional execute() method of your Action to test the preset values:

        InnerObject innerObj1 = new InnerObject();
        innerObj1.setInnerField("Inner Value 1");

        ArrayList<InnerObject> innerObjArrayList = new ArrayList<InnerObject>();
        innerObjArrayList.add(innerObj1);

        OuterObject outerObj1 = new OuterObject();      
        outerObj1.setInnerObjects(innerObjArrayList);

        outerObjects = new ArrayList<OuterObject>();
        outerObjects.add(outerObj1);

the JSP:

    <s:form>
        <s:textfield name="outerObjects[0].innerObjects[0].innerField" />
        <s:submit/>
    </s:form>

(when iterating, simply use [%{#stat.index}] for Lists and ['%{#stat.index}'] for Maps)

The same solution is applicable for every kind of iterable structure (probably except the Guava stuff that needs the .create() method to be invoked).

Of course this is not handy in every case, in your example you have already a huge structure and this will almost double it, but it works, it's OOP, your OGNL will be clearer (because of names) and however seems to be the only way.

Note: the Classes must be real stand-alone Classes, not Inner Classes, another case where OGNL fails to autowire the objects.

Hope that helps

---

EDIT

What you need then, is only one more level:

change this:

private TreeMap<String,List<ObjectC>> allPlainFields;

to this

private TreeMap<String,ObjectX> allPlainFields;

and create an ObjectX containing a private field that is a List<ObjectC>.

It will work.

Answer 2

According to your latest update. If you are using TreeMap Struts2 cannot correctly determine type of elements inside it. Change declaration of testTreeMap from TreeMap to Map.

private Map<String,ObjectCList> testTreeMap = new TreeMap<String,ObjectCList>();

Or annotate testTreeMap with com.opensymphony.xwork2.util.Element annotation to tell Struts2 what type are elements inside map.

@Element(value = ObjectCList.class)
private TreeMap<String,ObjectCList> testTreeMap = new TreeMap<String,ObjectCList>();