Package jakarta.mvc.engine

Interface ViewEngine

  • public interface ViewEngine

    View engines are responsible for processing views and are discovered using Jakarta Contexts and Dependency Injection. Implementations must look up all instances of this interface, and process a view as follows:

    1. Gather the set of candidate view engines by calling supports(String) and discarding engines that return false.
    2. Sort the resulting set of candidates using priorities. View engines can be decorated with Priority to indicate their priority; otherwise the priority is assumed to be PRIORITY_APPLICATION.
    3. If more than one candidate is available, choose one in an implementation-defined manner.
    4. Fire a BeforeProcessViewEvent event.
    5. Call method processView(ViewEngineContext) to process view.
    6. Fire a AfterProcessViewEvent event.

    The default view engines for Jakarta Server Pages and Facelets use file extensions to determine support. Namely, the default Jakarta Server Pages view engine supports views with extensions jsp and jspx, and the one for Facelets supports views with extension xhtml.

    Since:
    1.0
    Author:
    Santiago Pericas-Geertsen, Ivar Grimstad
    See Also:
    Priority, BeforeProcessViewEvent

    • Field Detail

      • VIEW_FOLDER

        static final String VIEW_FOLDER
        Name of property that can be set to override the root location for views in an archive.
        See Also:
        Application.getProperties(), Constant Field Values

      • PRIORITY_BUILTIN

        static final int PRIORITY_BUILTIN
        Priority for all built-in view engines.
        See Also:
        Constant Field Values

      • PRIORITY_FRAMEWORK

        static final int PRIORITY_FRAMEWORK
        Recommended priority for all view engines provided by frameworks built on top of MVC implementations.
        See Also:
        Constant Field Values

      • PRIORITY_APPLICATION

        static final int PRIORITY_APPLICATION
        Recommended priority for all application-provided view engines (default).
        See Also:
        Constant Field Values

    • Method Detail

      • supports

        boolean supports​(String view)
        Returns true if this engine can process the view or false otherwise.
        Parameters:
        view - the view.
        Returns:
        outcome of supports test.

      • processView

        void processView​(ViewEngineContext context)
          throws ViewEngineException

        Process a view given a ViewEngineContext. Processing a view involves merging the model and template data and writing the result to an output stream.

        Following the Jakarta EE threading model, the underlying view engine implementation must support this method being called by different threads. Any resources allocated during view processing must be released before the method returns.

        Parameters:
        context - the context needed for processing.
        Throws:
        ViewEngineException - if an error occurs during processing.