Dynamic Fields on JSF

Question

I need to perform a web service (method) call just before load of a jsf page. The call will return a list of input fields that have to be displayed on my jsf page. The user can fill in the form and on click of next I need the values entered on the form to be sent back to another web service (method). My approach was to have a request scoped bean for the jsf page(which consists of a blank form and a binding to the bean), and perform the web service call in the setter method of my form method and dynamically create UIInput fields

//call web service
//Loop
    UIInput input = new HtmlInputText();
    //set unique Id
    form.getChildren().add(input);
//End Loop

It does create the Input fields, but if I perform browser back or refresh it keeps adding Input fields. So clearly my approach is wrong.
Also I found out that when I try to get the values for these dynamically created Input fields on Submit action like

List<UIComponent> dynamicFields = form.getChildren();
 for(int i=0;i<form.getChildCount();i++){   
     if("javax.faces.Input".equals(componentFamily)){
        UIInput input = (UIInput)dynamicFields.get(i);
        System.out.println("Input Field: ID = "+input.getId() + " , Value="+ input.getValue());
      }
 }

The Id of the fields is printed properly, However value is always null. Clearly doing it all wrong.

Kindly let me know when and at what point do I create fields and how do I capture those values P.S Am using JSF 2.0, Jdeveloper, Glassfish and/or Weblogic Server

Answer 1

From your question I was not able to be sure about what kind of data you expect to get from your webservice, and what kind of component you want to render it in. My answer below assumes that you will always receive a list of String and that you will display them in text boxes.

One possible approach would be to call your webservice and fetch the data in a @PostConstruct method, put this data into a list, and then render the data in a data table. Code below.

Bean:

@ManagedBean(name="bean")
@ViewScoped
public class YourBean implements Serializable {


private static final long serialVersionUID = 1L;

private List<String> values = new ArrayList<String>();

   //The method below @PostConstruct is called after the bean is instantiated
   @PostConstruct
   public void init(){
          //fetch data from source webservice, save it to  this.values
   }

   public void save(){
        for(String s: this.values)
            // send s to destination webservice
   }

   public List<String> getValues(){
         return this.values;
   }  

   public void setValues(List<String> values){
         this.values = values;
   }       

}

XHTML excerpt:

<h:form>
     <h:dataTable value="#{bean.values}" var="s">
          <h:column>
                <h:inputText value="#{s}" />
          </h:column>
     </h:dataTable>
     <h:commandButton value="Save" action="#{bean.save}" />
</h:form>

Answer 2

This problem because the scope of your bean you are binding on it if it is @RequestScoped this means that every time you refresh or call the page you are going to invoke the post constuctor (@PostConstuct) method again so do the job of the creation again and for the null value of the input fields you should add to every input field value expression to store the value in it.

    private String inputValue; //setter() getter()
    UIInput input = new HtmlInputText(); 

   @PostCostruct
   public void addInput()
     {
        // your previos create and add input fields to the form + setting value expression
        Application app = FacesContext.getCurrentInstance().getApplication();  
        input.setValueExpression("value",app.getExpressionFactory().createValueExpression(
                   FacesContext.getCurrentInstance().getELContext(), "#{bean.inputValue}", String.class));
     }

The correct answer if you are using binding don't use Request scope use Session Scope and it will work with you and get data not null when retrieve values.