java/src/main/com/google/appengine/api/taskqueue/DeferredTaskContext.java

   1 // Copyright 2011 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.taskqueue;
   4
   5 import com.google.apphosting.api.ApiProxy;
   6
   7 import java.util.Map;
   8
   9 import javax.servlet.http.HttpServlet;
  10 import javax.servlet.http.HttpServletRequest;
  11 import javax.servlet.http.HttpServletResponse;
  12
  13 /**
  14  * Resources for managing {@link DeferredTask}.
  15  *
  16  */
  17 public class DeferredTaskContext {
  18   /**
  19    * The content type of a serialized {@link DeferredTask}.
  20    */
  21   public static final String RUNNABLE_TASK_CONTENT_TYPE =
  22       "application/x-binary-app-engine-java-runnable-task";
  23
  24   /**
  25    * The URL the DeferredTask servlet is mapped to by default.
  26    */
  27   public static final String DEFAULT_DEFERRED_URL = "/_ah/queue/__deferred__";
  28
  29   static final String DEFERRED_TASK_SERVLET_KEY =
  30     DeferredTaskContext.class.getName() + ".httpServlet";
  31   static final String DEFERRED_TASK_REQUEST_KEY =
  32     DeferredTaskContext.class.getName() + ".httpServletRequest";
  33   static final String DEFERRED_TASK_RESPONSE_KEY =
  34     DeferredTaskContext.class.getName() + ".httpServletResponse";
  35   static final String DEFERRED_DO_NOT_RETRY_KEY =
  36     DeferredTaskContext.class.getName() + ".doNotRetry";
  37
  38   /**
  39    * Returns the {@link HttpServlet} instance for the current running
  40    * deferred task for the current thread or {@code null} if there is
  41    * no current deferred task active for this thread.
  42    */
  43   public static HttpServlet getCurrentServlet() {
  44     Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  45     return (HttpServlet) attributes.get(DEFERRED_TASK_SERVLET_KEY);
  46   }
  47
  48   /**
  49    * Returns the {@link HttpServletRequest} instance for the current running
  50    * deferred task for the current thread or {@code null} if there is
  51    * no current deferred task active for this thread.
  52    */
  53   public static HttpServletRequest getCurrentRequest() {
  54     Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  55     return (HttpServletRequest) attributes.get(DEFERRED_TASK_REQUEST_KEY);
  56   }
  57
  58   /**
  59    * Returns the {@link HttpServletResponse} instance for the current running
  60    * deferred task for the current thread or {@code null} if there is
  61    * no current deferred task active for this thread.
  62    */
  63   public static HttpServletResponse getCurrentResponse() {
  64     Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  65     return (HttpServletResponse) attributes.get(DEFERRED_TASK_RESPONSE_KEY);
  66   }
  67
  68   /**
  69    * Sets the action on task failure. Normally when an exception is thrown,
  70    * the task will be retried, however if {@link #setDoNotRetry}(false) is
  71    * set, the task will not be retried.
  72    */
  73    public static void setDoNotRetry(boolean value) {
  74      Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  75      attributes.put(DEFERRED_DO_NOT_RETRY_KEY, value);
  76    }
  77
  78    private DeferredTaskContext() {}
  79 }