JSF Converter入門 - カスタムConverterの実装

package mypackage;

import java.util.ArrayList;
import java.util.List;

import javax.faces.convert.Converter;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;

public class String2ListConverter implements Converter{
    //Converter ID
    public static final String CONVERTER_ID = "String2List";

    //String型⇒Object型
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        if(value == null || value.equals("")){
            return value;
        }

        String [] items = value.split(",");
        List retList = new ArrayList();
        for (String item : items) {
            if (!"".equals(item)) {
                retList.add(item);
            }
        }
        
        return retList;
    }
    
    //Object型⇒String型
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        assert value instanceof List;
        
        String ret = "";
        List <String>valueList = (List)value;
        for (int i=0; i<valueList.size(); i++) {
            String item = (String)valueList.get(i);
            ret += item;
            
            if (i != valueList.size()-1) {
                ret += ",";
            }
        }
        return ret;
    }
    
    // parameters here
    private String param1;
    public void setParam1(String param1) {
        this.param1 = param1;
    }

    public String getParam1() {
        return param1;
    }
    //...
}