java/src/main/com/google/appengine/api/utils/SystemProperty.java

   1 // Copyright 2009 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.utils;
   4
   5 /**
   6  * Global system properties which are set by App Engine.
   7  * <p>
   8  * Example code:
   9  * <pre>
  10  * if (SystemProperty.environment.value() == SystemProperty.Environment.Value.Production) {
  11  *   // do something that's production-only
  12  * }
  13  * String version = SystemProperty.version.get();
  14  * </pre>
  15  *
  16  */
  17 public class SystemProperty {
  18
  19   /**
  20    * The current executing environment. Has the key,
  21    * {@code "com.google.appengine.runtime.environment"}.
  22    * Has the values {@code "Production"} and {@code "Development"}.
  23    */
  24   public static final Environment environment = new Environment();
  25
  26   /**
  27    * The current executing runtime version. Has the key,
  28    * {@code "com.google.appengine.runtime.version"}.
  29    * A Version value is composed of period-separated integers, for example,
  30    * "1.2.8".
  31    */
  32   public static final SystemProperty version =
  33       new SystemProperty("com.google.appengine.runtime.version");
  34
  35   /**
  36    * The application identifier for the current application.  Has the
  37    * key, {@code "com.google.appengine.application.id"}.
  38    */
  39   public static final SystemProperty applicationId =
  40       new SystemProperty("com.google.appengine.application.id");
  41
  42   /**
  43    * The version identifier for the current application version.  Result is of
  44    * the form {@literal <major>.<minor>} where {@literal <major>} is the version
  45    * name supplied at deploy time and {@literal <minor>} is a timestamp value
  46    * maintained by App Engine. Has the key
  47    * {@code "com.google.appengine.application.version"}.
  48    */
  49   public static final SystemProperty applicationVersion =
  50       new SystemProperty("com.google.appengine.application.version");
  51
  52   /**
  53    * @deprecated Use {@link
  54    *             com.google.appengine.api.modules.ModulesService#getCurrentInstanceId()}
  55    */
  56   @Deprecated
  57   public static final SystemProperty instanceReplicaId =
  58     new SystemProperty("deprecated");
  59
  60   /**
  61    * The current executing environment. Has the key,
  62    * {@code "com.google.appengine.runtime.environment"}.
  63    * The set of values are specified by {@link Environment.Value Value}.
  64    */
  65   public static class Environment extends SystemProperty {
  66
  67     /**
  68      * The set of possible values for Environment.
  69      */
  70     public enum Value {
  71       Production,
  72       Development;
  73
  74       public String value() {
  75         return toString();
  76       }
  77     }
  78
  79     private Environment() {
  80       super("com.google.appengine.runtime.environment");
  81     }
  82
  83     /**
  84      * Returns the Value that the SystemProperty is set to.
  85      *
  86      * @return null if the Environment is not set, or is set to a value that
  87      * does not correspond to any predefined {@code Value}.
  88      */
  89     public Value value() {
  90       try {
  91         String propertyValue = get();
  92         return propertyValue != null ? Value.valueOf(get()) : null;
  93       } catch (IllegalArgumentException e) {
  94         return null;
  95       }
  96     }
  97
  98     /**
  99      * Sets the Environment to {@code value}. Equivalent to
 100      * {@code set(value.value())}.
 101      *
 102      */
 103     public void set(Value value) {
 104       set(value.value());
 105     }
 106   }
 107
 108   private SystemProperty(String key) {
 109     this.key = key;
 110   }
 111
 112   private String key;
 113
 114   /**
 115    * The key for the system property.
 116    */
 117   public String key() {
 118     return key;
 119   }
 120
 121   /**
 122    * Gets the value of the system property.
 123    * Equivalent to {@code System.getProperty(key())}.
 124    */
 125   public String get() {
 126     return System.getProperty(key());
 127   }
 128
 129   /**
 130    * Sets the value of the system property.
 131    * Equivalent to {@code System.setProperty(key(), value)}.
 132    */
 133   public void set(String value) {
 134     System.setProperty(key(), value);
 135   }
 136 }