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   static final String DEFERRED_MARK_RETRY_KEY =
  38     DeferredTaskContext.class.getName() + ".markRetry";
  39
  40   /**
  41    * Returns the {@link HttpServlet} instance for the current running
  42    * deferred task for the current thread or {@code null} if there is
  43    * no current deferred task active for this thread.
  44    */
  45   public static HttpServlet getCurrentServlet() {
  46     Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  47     return (HttpServlet) attributes.get(DEFERRED_TASK_SERVLET_KEY);
  48   }
  49
  50   /**
  51    * Returns the {@link HttpServletRequest} instance for the current running
  52    * deferred task for the current thread or {@code null} if there is
  53    * no current deferred task active for this thread.
  54    */
  55   public static HttpServletRequest getCurrentRequest() {
  56     Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  57     return (HttpServletRequest) attributes.get(DEFERRED_TASK_REQUEST_KEY);
  58   }
  59
  60   /**
  61    * Returns the {@link HttpServletResponse} instance for the current running
  62    * deferred task for the current thread or {@code null} if there is
  63    * no current deferred task active for this thread.
  64    */
  65   public static HttpServletResponse getCurrentResponse() {
  66     Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  67     return (HttpServletResponse) attributes.get(DEFERRED_TASK_RESPONSE_KEY);
  68   }
  69
  70  /**
  71    * Sets the action on task failure. Normally when an exception is thrown,
  72    * the task will be retried, however if {@code setDoNotRetry}
  73    * is set to {@code true}, the task will not be retried.
  74    */
  75    public static void setDoNotRetry(boolean value) {
  76      Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  77      attributes.put(DEFERRED_DO_NOT_RETRY_KEY, value);
  78    }
  79
  80  /**
  81    * Request a retry of this task, even if an exception was not thrown.
  82    * If an exception was thrown and {@link #setDoNotRetry} is set to {@code true}
  83    * the request will not be retried.
  84    */
  85    public static void markForRetry() {
  86      Map<String, Object> attributes = ApiProxy.getCurrentEnvironment().getAttributes();
  87      attributes.put(DEFERRED_MARK_RETRY_KEY, true);
  88    }
  89
  90    private DeferredTaskContext() {}
  91 }