Resources

A WResource is a target for an HTTP request. It specifies application-dependent content that may be generated by your application on demand. This allows you to serve auxiliary objects related to a particular application or application session, and perhaps dynamically generate the content. There are different type of resources which can serve an HTTP request:

You can deploy a resource depending on the scope:

  • Deploy a private resource if access should be limited to a session (single user access).
  • Deploy a global resource if access should always be possible (e.g. a web service).

By default, a resource is private to an application; access to it is protected by same secret session ID that protects any other access to the application.

You can help the browser to start a suitable helper application to handle the downloaded resource, or suggest to the user a suitable filename for saving the resource, by setting an appropriate file name using suggestFileName().

To serve resources that you create on the fly, you need to specialize the WResource class and implement handleRequest().

Because of the nature of the web, a resource may be requested one time or multiple times at the discretion of the browser, and therefore your resource should in general not have any side effects except for what is needed to render its own contents. Unlike event notifications to a JWt application, resource requests are not serialized, but are handled concurrently. You need to grab the application lock if you want to access or modify other widget state from within the resource.

Example
source 
  class MyResource extends WResource {
    private static Logger logger = LoggerFactory.getLogger(MyResource.class);

    MyResource() {
      super();
      this.suggestFileName("data.txt");
    }

    void handleRequest(final WebRequest request, final WebResponse response) throws IOException {
      response.setContentType("plain/text");
      response.out().append("I am a text file.").append('\n');
    }
  }

  void ResourceCustom() {
    WContainerWidget container = new WContainerWidget();
    MyResource textResource = new MyResource();
    WLink link = new WLink(textResource);
    link.setTarget(LinkTarget.NewWindow);
    WAnchor anchor = new WAnchor(link, "Download file", (WContainerWidget) container);
  }

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Static resources

Static resources are global which means that they are available as long as the application is running. A web service (e.g. REST, SOAP, WSDL) is a typical example of a resource that should always be available. This could be needed for machine-to-machine communication, etc.

Use WServer.addResource() to deploy static resources.

Example
source 
  void ResourceStatic() {
    WContainerWidget container = new WContainerWidget();
  }

Classes such as WAnchor or WImage can use a resource instead of a URL to provide their contents. So, in any widget where you pass a WLink, you can refer to a resource. You can find several examples in the widget gallery:

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