title: How to map document with dynamic keys to a Spring MongoDb entity class
body: <p>I have a document that can have dynamic key names:</p>
  
  <pre><code>{
  "_id" : ObjectId("51a29f6413dc992c24e0283e"),
  "envinfo" : {
      "appName" : "MyJavaApp",
      "environment" : {
          "cpuCount" : 12,
          "heapMaxBytes" : 5724766208,
          "osVersion" : "6.2",
          "arch" : "amd64",
          "javaVendor" : "Sun Microsystems Inc.",
          "pid" : 44996,
          "javaVersion" : "1.6.0_38",
          "heapInitialBytes" : 402507520,
  }
  </code></pre>
  
  <p>Here <code>envinfo</code> 's keys are not known in advance.
  What is the best way to create an entity class in Spring Data Mongodb which will map this document?</p>