struts2-jquery-tree-plugin + json

Front-end
#1

Srs(a),

Estou tentando aprender como funciona o plugin struts2-jquery-tree-plugin com o exemplo do proprio site.
Quando clico no nó da árvore, o navegador abre o json, criado na action, como texto. Não é “processado” como
se fosse novos nós. O jsp estaria incompleto?

jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="s" uri="/struts-tags"%>    
<%@ taglib prefix="sj" uri="/struts-jquery-tags"%>
<%@ taglib prefix="sjt" uri="/struts-jquery-tree-tags"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>

 <sjt:tree>
        <s:url id="treeDataUrl" action="jsonTreeData"/>
        <sjt:treeItem
        		title="json1" 
                id="jsonTree" 
                href="%{treeDataUrl}"
                onClickTopics="treeClicked" 
                
        />
</sjt:tree>   
      
</body>
</html>

java action

@ParentPackage( value="json-default")
public class JsonTreeDataAction {

	private List<TreeNode> nodes = new ArrayList<TreeNode>();
	private String id = "";
	
	@Action(value = "jsonTreeData", results = {
			@Result(name = "ok", type = "json", params = {
					"root", "nodes" })
			})	
	public String execute() {
		
		System.out.println("ACTION");
		TreeNode nodeA = new TreeNode();
        nodeA.setId("A" + id);
        nodeA.setTitle("Node A" + id);
        nodeA.setState(TreeNode.NODE_STATE_CLOSED);

        TreeNode nodeB = new TreeNode();
        nodeB.setId("B" + id);
        nodeB.setState(TreeNode.NODE_STATE_CLOSED);
        nodeB.setTitle("Node B" + id);

        TreeNode nodeC = new TreeNode();
        nodeC.setId("C" + id);
        nodeC.setState(TreeNode.NODE_STATE_CLOSED);
        nodeC.setTitle("Node C" + id);

        nodes.add(nodeA);
        nodes.add(nodeB);
        nodes.add(nodeC);
        
		return "ok";
	}
	
	public String getJSON() {
		return execute();
	}

	public List<TreeNode> getNodes() {
		return nodes;
	}

	public void setId(String id) {
		this.id = id;
	}
}

Desde já agradeço,

#2