Thursday, November 19, 2009

Sinek, spreadsheet component, for JSF 2

Here are some notes on developing a spreadsheet component for JSF. Here is how it looks like :Cells contents are being updated with ajax, user is able to add rows/columns by clicking the buttons on the bottom-right corner. I am calling this component 'sinek'. Probably I will rename it later. To check the source code click here.
Here are the parts that make up the component :
  • org.mca.sinek.jsf
This package has 3 files that make up the main component. UISinek, SinekRenderer and WorkSheet.
  • WorkSheet is the datamodel. Its basically a two dimensioned array of Strings:
 public class WorkSheet {
List<List<String>> sheet;
public Integer getNumOfColumns() {
public int getNumOfRows() {
public List<String> addEmptyRow() {
public void addEmptyCol() {
It also has methods that return the number of rows, add rows/cols.
  • UISinek is the component that holds the state values. After its added to view it adds the sheet cells as its children. Cells are made up of inputtext components :
 @FacesComponent(value = "sinek")
@ListenerFor(systemEventClass = PostAddToViewEvent.class)
@ResourceDependency(name = "jsf.js", library = "javax.faces", target = "body")
public class UISinek extends UIInput {
public void processEvent(ComponentSystemEvent event) throws AbortProcessingException {
Map<String, String> requestParameterMap = getFacesContext().getExternalContext()
String exec = requestParameterMap.get("javax.faces.source");
if((getClientId()+ "_addr").equals(exec)) {
} else if((getClientId()+ "_addc").equals(exec)) {
int count = getChildCount();
private void createRow(List<String> row, int rindex) {
ValueExpression ve = this.getValueExpression("value");
String exp = ve.getExpressionString();
exp = exp.substring(0, exp.length() - 1);
int cl = 0;
for (String cell : row) {
String id = getId() + "_" + rindex + "_" + cl;
if(findComponent(id) != null) {
HtmlInputText in = new HtmlInputText();
ValueExpression el = ELUtils.createValueExpression(exp + ".sheet[" + rindex + "][" + cl + "]}");
in.setValueExpression("value", el);
We are annotating it with the @FaceComponent annotation. It listens for the PostAddToViewEvent with the @ListenFor annotation. When the event fires processEvent method will be fired. Process events creates HtmlInputText components whose values are backed up with the datamodel. Also sets up the ajax call which will update the component values. Because we will be using ajax we have to define it with the @ResourceDependency annotation. The "javax.faces.source" will be used to identify the add col/row events.
  • SinekRenderer is the renderer. It renders our cells into the cells of a table:
 @FacesRenderer(rendererType = "sinek", componentFamily = "javax.faces.Input")
@ResourceDependency(name = "sinek.css", library = "org.mca", target = "head"),
@ResourceDependency(name = "jsf.js", library = "javax.faces", target = "body")})
public class SinekRenderer extends Renderer {
public void encodeBegin(FacesContext facesContext, UIComponent comp) throws IOException {
UISinek sinek = (UISinek) comp;
ResponseWriter writer = facesContext.getResponseWriter();
writer.write("<table id=\"" +sinek.getClientId()+"\" class=\"mctable\">");
int R = sinek.getWorkSheet().getNumOfColumns();
renderFooter(writer, R, sinek);
renderColumnHeaders(writer, R);
renderCells(facesContext, writer, sinek);
private void renderCells(FacesContext facesContext, ResponseWriter writer, UISinek sinek) throws IOException {
int i = 0;
int rno = 1;
int r = sinek.getWorkSheet().getNumOfColumns();
List<UIComponent> rows = sinek.getChildren();
for (UIComponent c : rows) {
if (i % r == 0) {
if (i % 2 == 1) {
writer.write("<tr class=\"altrow\">");
} else {
rno = renderRowHeader(writer, rno);
if (i % r == (r - 1)) {
public void encodeChildren(FacesContext context, UIComponent component) throws IOException {
public boolean getRendersChildren() {
return true;
Renderers are defined with the @FacesRenderer annotation and again @ResourceDependecy annotation is used for the css and ajax scripts. It renderers the children (cells) so we need to override the encodeChildren and getRendersChildren methods.
  • mca.taglib.xml : Defines the namespace and components.
  • sinek.css : Style sheet for our project.
My example also contains Hello class which is a example bean used on page index.xhtml.
Thats all for now drop me a line if you need more info and be sure to check-out the source.

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