I am writing a custom Facelets TagHandler that can be used in Facelets view .xhtml files. Inside the apply method, I am trying to access faceletContext.getFacesContext().getResponseWriter(), but it returns null.

Please note that I am not using managed beans. I am using plain servlets, but utilizing Facelets templates.

public class MyTag extends TagHandler {

  public MyTag(TagConfig config) {
    super(config);
  }

  @Override
  public void apply(FaceletContext ctx, UIComponent parent) throws IOException {
    // ctx.getFacesContext().getResponseWriter() return Null here
  }
 
}

Please note that all configurations for the custom tag have been set up properly, and I have confirmed that the apply method is being executed. However, getResponseWriter() still returns null.

UPDATE: The reason I wanted to access the getResponseWriter() is that I need to write some HTML code to the response output. I also tried using the PrintWriter of the current response inside the apply method, but it did not work.

Any help? Thanks!

I am writing a custom Facelets TagHandler that can be used in Facelets view .xhtml files. Inside the apply method, I am trying to access faceletContext.getFacesContext().getResponseWriter(), but it returns null.

Please note that I am not using managed beans. I am using plain servlets, but utilizing Facelets templates.

public class MyTag extends TagHandler {

  public MyTag(TagConfig config) {
    super(config);
  }

  @Override
  public void apply(FaceletContext ctx, UIComponent parent) throws IOException {
    // ctx.getFacesContext().getResponseWriter() return Null here
  }
 
}

Please note that all configurations for the custom tag have been set up properly, and I have confirmed that the apply method is being executed. However, getResponseWriter() still returns null.

UPDATE: The reason I wanted to access the getResponseWriter() is that I need to write some HTML code to the response output. I also tried using the PrintWriter of the current response inside the apply method, but it did not work.

Any help? Thanks!

• jsf
• facelets
• tag-handler

2 Answers 2

Tag handlers build the view. They don't render the view. Use a Renderer instead, usually in combination with an UI component. Or simply use a tag file (with JSTL), especially as you ultimately don't seem to want to use UI components.

If you tell more about the concrete functional requirement (i.e. what exactly are you ultimately trying to achieve), then we may be able to give a more specific answer/direction.

See also:

• What's the view build time?
• When to use <ui:include>, tag files, composite components and/or custom components?

Update: it appears you wish to compute a chunk of HTML with Java and render it unescaped. In that case, the simplest approach is creating a @RequestScoped bean and preparing the HTML in @PostConstruct and then using a <h:outputText escape="false"> to render it.

@Named
@RequestScoped
public class Bean {

    private String html;

    @PostConstruct
    public void init() {
        html = computeHtmlSomehow();
    }

    public String getHtml() {
        return html;
    }
}

<ui:composition 
    xmlns:ui="jakarta.faces.facelets" 
    xmlns:h="jakarta.faces.html">
    ...
    <h:outputText value="#{bean.html}" escape="false" />
    ...
</ui:composition>

The logic is complex because it relies on the underlying Servlet-based MVC framework developed by my company

Alternatively, you can also manually construct the bean and just let that servlet set it as a request attribute before forwarding to the Facelets page as instructed in your previous question How to set up a Facelets template for a Jakarta Servlet web application (not a Jakarta Faces application)

request.setAttribute("bean", bean);

See also:

• Component to inject and interpret String with HTML code into JSF page

I found out the solution is to not use: ctx.getFacesContext().getResponseWriter().

public class MyTag extends TagHandler {

  public MyTag(TagConfig config) {
    super(config);
  }

  @Override
  public void apply(FaceletContext ctx, UIComponent parent) throws IOException {
    // Prepare for html code
    // This can be complete html code of div, label, input, table, etc.
    String htmlCode = ...

    // HtmlOutputText
    HtmlOutputText ui = new HtmlOutputText();
    ui.setTransient(true); // Stateless
    ui.setEscape(false);   // Will render raw html into the response.

    // The value of this ui is the html code generated above
    ui.setValue(htmlCode);

    // Add ui into the parent
    parent.getChildren().add(ui);
  }
 
}