How to obtain <dmf:listbox> values inside java class?

vsoman1984

Hi All,

I have my JSP page which obtains user entered values and utilizes them to be sent as parameters to a function inside the governing java class.

So my custom elements are as follows

JSP - sendToDistributionList.jsp

JAVA - DummyComponent.java

The JSP has a list box to obtain multiple values from the user.

<dmf:panel name="test">

<tr><td align="right">
<dmf:listbox width="180" name="<%=DummyComponent.TARLANG_LISTBOX_CONTROL_NAME%>" size='5' multiselect='true' cssclass='BrowseNumberList' runatclient='true' >

<dmf:option id = "item1" value="fr-fr" label="French(France)" />
<dmf:option id = "item2" value="zh-cn" label="Chinese(Simplified)" />
<dmf:option id = "item3" value="zh-tw" label="Chinese(Taiwan)" />
<dmf:option id = "item4" value="da-dk" label="Danish" />

</dmf:listbox>

</dmf:panel>
</td></tr>
</td>
</tr>

In the class file i have assumed that the control will be simply acessing the user selected values and passing them through "DummyComponent.TARLANG_LISTBOX_CONTROL_NAME".So i declared the String in the class file and wrote a function to obtain the user selected multiple values.

public

static final String TARLANG_LISTBOX_CONTROL_NAME = "_TARLANG_LISTBOX_CONTROL_NAME";

private String [] tarLang ;

...

private

String[]readTarLanguages(){ListBox control = (ListBox)getControl(

"__TARLANG_LISTBOX_CONTROL_NAME");

if (control != null){

tarLang = control.getParameterNames();

}

System.

out.println("This is Target Language" + tarLang[1]);

return tarLang;}

To check whether the user entered value has been captured i wrote the Sysout "System.out.println("This is Target Language" + tarLang[1]);".

This is where i am getting my Null Pointer exception.

I am not sure where the errors is. Is it in the JSP at the location of values acquisition?Or is it in using the control.getParameterNames(); inside my class?

Could any one kindly guide me as to where i can rectify the mistake.

Thank You

Regards.

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Accepted answers

dnvhariprasad

Yeap. You can use like that. in almost all wdk components the name will be like that only...

All comments

apriam_i

Hello!

Try to change "tarLang = control.getParameterNames();" to "tarLang=control.getValue();"

vsoman1984

Hi Alexey,

control.getValue(); returns a string.

So will it be containing the multiple values selected by the user?Or do u suggest to deploy a for loop to extract each value?

Thank You

vsoman1984

Hi All,

I could not find any handy examples with multiselect='true' for listboxes to iterate through the selected elements.

I have come across dmf:multiselector tag. Can this be a substitute for Listbox.

Does anyone have information regarding this.

Hoping for ur help

Thank You

dnvhariprasad

The multiselect attribute is only available if you retrieve the value in client‑side JavaScript.

Multiple selections are not passed to the component, because no server event is fired. For an

example of a client‑side implementation that retrieves multiple selections in the listbox, refer to

searchsources_preferences.jsp and changesearchsources.jsp.

dnvhariprasad

You can use multiselector if you dont have choice to insert your logic at client side.

the following is from WDK reference guide.

UsageThe component can retrieve a list of selected items from the control by calling getSelectedItems() onthe control. The buttons trigger client side events so that the client doesn’t have to make a round tripto the server every time a button is selected. When a trip to the server is made the control will updateits data on the server side via a hidden field that keeps an updated item list.The List object that holds items has the following features:• Each element in a List represents one item.• The element can be a String, which is a value with no label.• The element can be an array of one String• A serialized list of items can be an array of one string (value) or two strings (value and label).If you supply the lists of available and selected columns in the JSP page, then the list must beserialized to a string before passing it in to the control. (You can create the serialized string from anArrayList using the MultiSelectorUtil class static method encodeItemList(). If you supply a list inyour component class, pass it in as ArrayList.In the following example from the VisibleRepositoryPreferences class, the class gets the controlson the JSP page, calls methods that get the ArrayList for each control, and initializes the items andselected items lists:public void onInit(ArgumentList args){super.onInit(args);...MultiSelector mltRepositories = (MultiSelector)getControl(REPOSITORY_SELECTOR, MultiSelector.class);mltRepositories.setSize("10");//Get selected connection broker and portDataDropDownList docbrokerControl = (DataDropDownList) getControl(CONTROL_DOCBROKER,DataDropDownList.class);Label docbrokerPortNumberControl = (Label) getControl(CONTROL_DOCBROKER_PORT,Label.class);//Get all repositories for this connection brokerArrayList arrDocbases = getInvisibleRepositories(docbrokerControl.getValue(), docbrokerPortNumberControl.getLabel());//Write the list to the available repositories listmltRepositories.setItems(arrDocbases);//Get previously selected repositories, set to selected items listmltRepositories.setSelectedItems(getVisibleRepositories());}

vsoman1984

Hi Hari,

Thank you for your helpful inputs as always.

I followed the searchsources_preferences.jsp and its behaviou class and the picture is a lot clearer now.Just one doubt remains from my side.I have got the list of elements to b displayed inside the listbox with me.They are not coming from any source like database etc. There are 22 elements in my List box

<dmf:listbox width="180" 
name="<%=DummyComponent.TARLANG_LISTBOX_CONTROL_NAME%>" size='5' 
multiselect='true'  cssclass='BrowseNumberList'  runatclient='true' > <dmf:option id = "item1" value="fr-fr" label="French(France)" /> 

<dmf:option id = "item2" value="zh-cn" label="Chinese(Simplified)" /> 

<dmf:option id = "item3" value="zh-tw" label="Chinese(Taiwan)" /> 

<dmf:option id = "item4" value="da-dk" label="Danish" /> 

<dmf:option id = "item5" value="nl-nl" label="Dutch(The Netherlands)" 
/> 
<dmf:option id = "item6" value="fr-ca" label="French(Canada)" /> 

<dmf:option id = "item7" value="de-de" label="Germany(Germany)" /> 

<dmf:option id = "item8" value="it-it" label="Italian(Italy)" 
/>
<dmf:option id = "item9" value="ja-jp" label="Japanese" 
/>
<dmf:option id = "item10" value="ko-kr" label="Korean" 
/>
<dmf:option id = "item11" value="nb-no" label="Norwegian(Bokmal)" 
/>
<dmf:option id = "item12" value="es-XL" label="Spanish(LAS)" 
/>
<dmf:option id = "item13" value="es-mx" label="Spanish(Mexico)" 
/>
<dmf:option id = "item14" value="es-es" label="Spanish(Spain)" 
/>
<dmf:option id = "item15" value="sv-se" label="Swedish" 
/>
<dmf:option id = "item16" value="nl-be" label="Flemish" 
/>
<dmf:option id = "item17" value="ru-ru" label="Russian(Russia)" 
/>
<dmf:option id = "item18" value="es-eu" label="Basque" 
/>
<dmf:option id = "item19" value="ca-es" label="Catalan" 
/>
<dmf:option id = "item20" value="en-gb" label="English(United 
Kingdom)" />
<dmf:option id = "item21" value="es-gl" label="Galician" 
/>
<dmf:option id = "item22" value="es-vl" label="Valencian" /> 

</dmf:listbox>

Observing the class and JSP of searchsources_preferences.jsp i am unclear as to how can i populate the list box with these values.

The client side javascript will iterate over the values in the listbox. But how will it obtain the values to be iterated over is my question.

The searchsources_preferences.jsp has

<td><dmf:listboxname='<%=SearchSourcesPreferences.CONTROL_REPOSITORY_LISTBOX%>'height="200" width="300" id='searchlistbox' size='12'multiselect="true"tooltipnlsid='MSG_REPOSITORIES_INCLUDED_SEARCH_PATH_TIP'onselect="getListBoxSelectedValues" runatclient="true"/></td>

as well as :

<dmf:hidden name="<%=SearchSourcesPreferences.CONTROL_LISTBOX_SELECTED_VALUES%>" id="listBoxSelectedValues"/>

mentioned in the JSP and the javascript:

functionvarvarforifif<%=strDocbaseSearchPathSeparator%>";}newText += document.forms[0].searchlistbox.options[j].value;}}document.forms[0].listBoxSelectedValues.value = newText;} (newText != ""){newText += " (option[j].selected){ (var j = 0; j < option.length; j++){ option = document.forms[0].searchlistbox.options; newText = ""; getListBoxSelectedValues (){

Can i place my set of 22 elements at the place (marked in orange) in the above snippet?

vsoman1984

Just to clarify by marked in orange i meant the following bolder code snippet:

<td><dmf:listbox name ='<%=SearchSourcesPreferences.CONTROL_REPOSITORY_LISTBOX%>'height ="200" width="300" id='searchlistbox' size='12'multiselect ="true"tooltipnlsid ='MSG_REPOSITORIES_INCLUDED_SEARCH_PATH_TIP'onselect ="getListBoxSelectedValues" runatclient="true"/></td>

Thank You

dnvhariprasad

You can just leave your listbox markup as it is. Option controls inside listbox will work.

You just need to define onselect attribute in your tag and create the function in javascript.

To get the values, you can take the help of getListBoxSelectedValues

vsoman1984

Hi Hari,

So i just need to leave my options inside the listbox.The name field for the listbox is required, will it be proper if i provide a placeholder name for the control for name like 'CLASSNAME.STRINGINSIDECLASS'.?

<dmf:panel name="test">

<tr><td align="right">
<dmf:listbox width="180" name="<%=CLASSNAME.STRINGINSIDECLASS(Placeholder)%>" size='5' multiselect='true' cssclass='BrowseNumberList' runatclient='true' >

<dmf:option id = "item1" value="fr-fr" label="French(France)" />
<dmf:option id = "item2" value="zh-cn" label="Chinese(Simplified)" />
...(remailing 20 options likewise)

</dmf:panel>
</td></tr>

</td>
</tr>
Really appreciate your help.

Thank You

dnvhariprasad

Yeap. You can use like that. in almost all wdk components the name will be like that only...

vsoman1984

Hi Hari

As always it did work

Zillion thanks.

Reached the solution by stating

dmf:listbox width="180" name="<%=DummyComponent.TARLANG_LISTBOX_CONTROL_NAME%>" size='5' multiselect='true' cssclass='BrowseNumberList' onselect="getListBoxSelectedValues" runatclient='true' id='searchlistbox'>

Thank You