Load JavaScript and CSS from Server Nearby

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DocumentationZK Developer's ReferencePerformance TipsLoad JavaScript and CSS from Server Nearby
Load JavaScript and CSS from Server Nearby

If some of the client machines are far away from the application server, we could set up a server near the clients to host ZK's JavaScript and CSS files, and then configure the application server to generate the URLs of JavaScript and CSS (and images it refers) from the server near the clients.


*Notice : the ZK static resource server is an application server which you deploy only official ZK library to, not your whole application.


  1. Implement the Encodes.URLEncoder
  2. Add library-property configuration to the zk.xml
    Document : ZK Configuration Reference/zk.xml/The Library Properties/org.zkoss.web.servlet.http.URLEncoder.
  3. Host ZK static resource server

Following is a sample :


    <value>org.zkoss.test.TestEncoder</value> <!-- Where the Implementation Class is -->


package org.zkoss.test;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import org.zkoss.web.servlet.http.Encodes.URLEncoder;
public class TestEncoder implements URLEncoder {

	public String encodeURL(ServletContext ctx, ServletRequest request, ServletResponse response,
	String uri, URLEncoder defaultEncoder) throws Exception {
		if (isStaticResource(uri)) {
			return getResourceHost() + uri.replace("~./", "");
		} else {
			return defaultEncoder.encodeURL(ctx, request, response, uri, defaultEncoder);
	 * file .wcs : CSS File
	 * file .wpd : Javscript File
	private boolean isStaticResource(String url) {
		// zul.lang.wpd should not be a static resource
		return url.startsWith("~./") && !url.endsWith("zul.lang.wpd") && (url.endsWith(".wpd") || url.endsWith(".wcs"));

	 * Detect where the ip is / who login / what kind of resource server
	 * @return the host name include protocol prefix. (Client will retrieve resource from it)
	private String getResourceHost() {
		return "http://SomeWhereNearbyMe/DefaultContext/zkau/web/";


Hosting ZK Static Resource

  1. Create a WAR with all ZK JARs only (without your application code)
  2. configure web.xml as a normal ZK application
  3. deploy such special ZK WAR to a server near your customer and add the URL to your implementation of URLEncoder.

Don't know how to deploy on server ? Please refer to Installation Guide.

Last Update : 2024/02/05

Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.