Package org.apache.commons.chain.web.javax

Class ChainServlet

java.lang.Object
javax.servlet.GenericServlet
javax.servlet.http.HttpServlet
org.apache.commons.chain.web.javax.ChainServlet
All Implemented Interfaces:
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:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final 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 final String
    CONFIG_CLASS_RESOURCE
    The name of the context init parameter containing a comma-delimited list of class loader resources to be scanned.
    static final String
    CONFIG_WEB_RESOURCE
    The name of the context init parameter containing a comma-delimited list of web application resources to be scanned.
    static final 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()
    The Default-Constructor for this class.

  • Method Summary

    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 Details

  • Constructor Details

    • ChainServlet

      public ChainServlet()
      The Default-Constructor for this class.

  • Method Details

    • 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, 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
      IOException - this exception is never thrown