Question

I have an array list named “newSymptomList” which contains a list of Symptom id’s (e.g. [1,3,4]) generated by a pick list target. I want to go through each symptom and get the relevant symptom name from the database although I’m stuck on the while loop.

PickList:

<rich:pickList id="plID" listWidth="10em" 
                        value="#{sym.newSymptomList}" 
                        sourceCaption="Symptoms" 
                        targetCaption="Selected Symptoms">
                    <!--List of all Symptoms-->
                    <f:selectItems value="#{sym.allSym}" var="c"
                                   itemLabel="#{c.symptomName}" itemValue="#{c.symptomId}"/>
</rich:pickList>

Relevant code in SymptomBean:

private List<Symptom> newSymptomList = new ArrayList<Symptom>();

public List getNewSymptomList()
{
  return newSymptomList;
}

public void setNewSymptomList(List<Symptom> newSymptomList )
{
  this.newSymptomList = newSymptomList; 
}

//Here is the code which returns a list of matching symptom names:

public List getSymNames() {
    List selectedSymptoms= new ArrayList(); 
    int i = 0;
    try
    {
        Class.forName("com.mysql.jdbc.Driver");
        con = ...
        ps = con.createStatement();
        rs = ps.executeQuery("select * from symptoms");
        while (rs.getString(1)== newSymptomList) {
            //getString(1) is symptomID and getString(2) is symptomName
            selectedSymptoms.add(i,new Symptom(rs.getString(1), rs.getString(2)));
            i++;
        }
    }//end of try

    catch (Exception e)
    {
        System.out.println("Error Data : " + e.getMessage());
    }

    return selectedSymptoms;
}

Answer 1

You’re going in the wrong direction as to achieving the requirement. You have the symptom names already there in the allSym list as referenced by <f:selectItems>. Your mistake is that you’re setting the selected symptoms as List<Symptom> while it should actually be a List<String> or whatever type the #{c.symptomId} actually is (it seems to be String as you’re attempting to get it by ResultSet#getString(), which is not a sane type, but that aside), otherwise you would get a ClassCastException when iterating over it.

Fix it accordingly:

private List<String> newSymptomList; // +getter+setter.

Finally, you could just go through the allSym list which you already have there in the same bean to get the Symptom objects.

List<Symptom> selectedSymptoms = new ArrayList<Symptom>();

for (Symptom symptom : allSym) {
    if (newSymptomList.contains(symptom.getSymptomId())) {
        selectedSymptoms.add(symptom);
    }
}

// ...

Another way is to keep the newSymptomList a real List<Symptom> and fix the itemValue of your <f:selectItems> to be #{c} instead of #{c.symptomId}. You only need to implement a javax.faces.converter.Converter so that JSF will be able to automatically convert between Symptom and its unique String representation. For an example, see also our <h:selectOneMenu> tag wiki page.