Package org.apache.commons.chain.web

Class ChainServlet

  • All Implemented Interfaces:
    java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig
    Direct Known Subclasses:
    ChainProcessor
    public class ChainServlet
extends javax.servlet.http.HttpServlet

    Servlet that automatically scans chain configuration files in the current web application at startup time, and exposes the result in a Catalog under a specified servlet context attribute. The following servlet init parameters are utilized:

    • org.apache.commons.chain.CONFIG_CLASS_RESOURCE - comma-delimited list of chain configuration resources to be loaded via ClassLoader.getResource() calls. If not specified, no class loader resources will be loaded.
    • org.apache.commons.chain.CONFIG_WEB_RESOURCE - comma-delimited list of chain configuration webapp resources to be loaded. If not specified, no web application resources will be loaded.
    • org.apache.commons.chain.CONFIG_ATTR - Name of the servlet context attribute under which the resulting Catalog will be created or updated. If not specified, it is expected that parsed resources will contain <catalog> elements (which will cause registration of the created Catalogs into the CatalogFactory for this application, and no servet context attribute will be created. NOTE - This parameter is deprecated.

    • org.apache.commons.chain.RULE_SET - Fully qualified class name of a Digester RuleSet implementation to use for parsing configuration resources (this class must have a public zero-args constructor). If not defined, the standard RuleSet implementation will be used.

    When a web application that has configured this servlet is started, it will acquire the Catalog under the specified servlet context attribute key, creating a new one if there is none already there. This Catalog will then be populated by scanning configuration resources from the following sources (loaded in this order):

    • Resources loaded from specified resource paths from the webapp's class loader (via ClassLoader.getResource()).
    • Resources loaded from specified resource paths in the web application archive (via ServetContext.getResource()).

    If no attribute key is specified, on the other hand, parsed configuration resources are expected to contain <catalog> elements, and the catalogs will be registered with the CatalogFactory for this web application.

    This class runs on Servlet 2.2 or later. If you are running on a Servlet 2.3 or later system, you should also consider using ChainListener to initialize your Catalog. Note that ChainListener uses parameters of the same names, but they are context init parameters instead of servlet init parameters. Because of this, you can use both facilities in the same application, if desired.

    Author:
    Matthew J. Sgarlata, Craig R. McClanahan, Ted Husted
    See Also:
    Serialized Form

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.lang.String CONFIG_ATTR
      The name of the context init parameter containing the name of the servlet context attribute under which our resulting Catalog will be stored.
      static java.lang.String CONFIG_CLASS_RESOURCE
      The name of the context init parameter containing a comma-delimited list of class loader resources to be scanned.
      static java.lang.String CONFIG_WEB_RESOURCE
      The name of the context init parameter containing a comma-delimited list of web applicaton resources to be scanned.
      static java.lang.String RULE_SET
      The name of the context init parameter containing the fully qualified class name of the RuleSet implementation for configuring our ConfigParser.

    • Constructor Summary

      Constructors 
      Constructor Description
      ChainServlet()  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void destroy()
      Clean up after ourselves as this application shuts down.
      void init()
      Create (if necessary) and configure a Catalog from the servlet init parameters that have been specified.
      void service​(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
      Does nothing; this servlet's only purpose is to initialize a Chain and store it in the servlet context.

      • Methods inherited from class javax.servlet.http.HttpServlet

        doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service

      • Methods inherited from class javax.servlet.GenericServlet

        getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • CONFIG_ATTR

        public static final java.lang.String CONFIG_ATTR

        The name of the context init parameter containing the name of the servlet context attribute under which our resulting Catalog will be stored.

        See Also:
        Constant Field Values

      • CONFIG_CLASS_RESOURCE

        public static final java.lang.String CONFIG_CLASS_RESOURCE

        The name of the context init parameter containing a comma-delimited list of class loader resources to be scanned.

        See Also:
        Constant Field Values

      • CONFIG_WEB_RESOURCE

        public static final java.lang.String CONFIG_WEB_RESOURCE

        The name of the context init parameter containing a comma-delimited list of web applicaton resources to be scanned.

        See Also:
        Constant Field Values

      • RULE_SET

        public static final java.lang.String RULE_SET

        The name of the context init parameter containing the fully qualified class name of the RuleSet implementation for configuring our ConfigParser.

        See Also:
        Constant Field Values

    • Constructor Detail

      • ChainServlet

        public ChainServlet()

    • Method Detail

      • destroy

        public void destroy()

        Clean up after ourselves as this application shuts down.

        Specified by:
        destroy in interface javax.servlet.Servlet
        Overrides:
        destroy in class javax.servlet.GenericServlet

      • init

        public void init()
          throws javax.servlet.ServletException

        Create (if necessary) and configure a Catalog from the servlet init parameters that have been specified.

        Overrides:
        init in class javax.servlet.GenericServlet
        Throws:
        javax.servlet.ServletException - if the servlet could not be initialized

      • service

        public void service​(javax.servlet.http.HttpServletRequest request,
                    javax.servlet.http.HttpServletResponse response)
             throws javax.servlet.ServletException,
                    java.io.IOException

        Does nothing; this servlet's only purpose is to initialize a Chain and store it in the servlet context.

        Overrides:
        service in class javax.servlet.http.HttpServlet
        Parameters:
        request - the request issued by the client
        response - the response to be returned to the cliengt
        Throws:
        javax.servlet.ServletException - (this exception is never thrown)
        java.io.IOException - (this exception is never thrown)