By default, wro4j provides 3 locators: ClasspathUriLocator, UrlUriLocator, ServletContextUriLocator. It is very unlikely that you would require a custom locator, because existing one covers almost all use-cases you may have.

Implement Custom Locator

But, in case you still need a custom one, just implement UriLocator interface:

public interface UriLocator {
  InputStream locate(final String uri) throws IOException;
  boolean accept(final String uri);

Configure Custom Locator

There are more options to configure custom locator with wro4j.

Using Custom managerFactory

The most low level approach is to create a custom WroManagerFactory which implements the UriLocatorFactory interface.

public class CustomWroManagerFactory extends BaseWroManagerFactory {
  protected UriLocatorFactory newUriLocatorFactory() {
    return new SimpleUriLocatorFactory().addUriLocator(new ServletContextUriLocator()).addUriLocator(new ClasspathUriLocator()).addUriLocator(
      new UrlUriLocator()).addUriLocator(new CustomUriLocator());

The last thing to do, is to configure CustomWroManager to be used by wroFilter or maven plugin

Using ConfigurableWroManagerFactory

ConfigurableWroManagerFactory allows a simplified configuration with aliases. The idea is that each locator has an associated alias and the locators can be configured in (the location and name of this file is configurable) like this:


It is possible to associated new (or even same) aliases with new custom locator implementations.

Using LocatorProvider

This option is available since 1.4.7. One option to provide custom associations of locator alias and corresponding implementation is to create a class which implements interface. For instance the default aliases are provided like this:

public class DefaultLocatorProvider
    implements LocatorProvider {
  public Map<String, UriLocator> provideLocators() {
    final Map<String, UriLocator> map = new HashMap<String, UriLocator>();
    map.put(ClasspathUriLocator.ALIAS, new ClasspathUriLocator());
    map.put(ServletContextUriLocator.ALIAS, new ServletContextUriLocator());
        new ServletContextUriLocator().setLocatorStrategy(LocatorStrategy.DISPATCHER_FIRST));
        new ServletContextUriLocator().setLocatorStrategy(LocatorStrategy.SERVLET_CONTEXT_FIRST));
    map.put(UrlUriLocator.ALIAS, new UrlUriLocator());
    return map;

Next step is to register that provider to make it visible by ConfigurableWroManagerFactory. To register it, add a file at the following location in project classpath:


Update the content of this file with a single line containing the fully qualified name of the your custom provider, example:


If you have more than one implementation of and want to register all of them, add each class name on the new line:


Using ConfigurableProvider

This option is available since 1.4.7. ro.isdc.wro.util.provider.ConfigurableProvider is an interface which extends and is useful when you want to provide not only locators but also other components like: processors, namingStrategy or hashStrategy.

The principle is the same, the only change is the provider implementation:

public class MyConfigurableProvider
    extends ConfigurableProviderSupport {
  public Map<String, UriLocator> provideLocators() {
    return //provide a map with custom locators

Notice that the DefaultConfigurableProvider extends ConfigurableProviderSupport which provides default implementation for all interfaces the ro.isdc.wro.util.provider.ConfigurableProvider extends.

The next step is to register that implementation as a service at the following location in the classpath:


with the fully qualified name of the custom provider class:


If you have more than one implementation of and want to register all of them, add each class name on the new line: