title: dynamodb: How to add auto increment numbers to key field while adding record to table
body: <p>I would like to add auto numbers to key field of table in dynamodb via console,
  e.g. 0,1,2,...</p>
  
  <p>I have <code>contact_us</code> table that I would like to have column with auto id increment.
  Please help me with this.</p>
  
  <pre><code>import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAutoGeneratedKey;
  import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBHashKey;
  import com.amazonaws.services.dynamodbv2.model.AttributeValue;
  
  public class ContactUs extends HttpServlet {
  
      String con_id;
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          try{
             // ...
             // ...
  
             Map&lt;String, AttributeValue&gt; item = newRecord();
             //System.out.println(item);
  
             // ...
  
             dbObject.addRecord(item, "contact_us");
  
          }catch (Exception e) {
             // TODO: handle exception
             e.printStackTrace();
          }
      }
  
      private Map&lt;String, AttributeValue&gt; newRecord() {
          Map&lt;String, AttributeValue&gt; item = new HashMap&lt;String, AttributeValue&gt;();
          con_id = getConID();
          dateTimeTimestamp = new SysDateTimeTimestamp();
          //Need to add con_id which will be auto id.
          item.put("con_id", new AttributeValue(con_id));
          // ...
          // ...
  
          return item;
      }
  
      @DynamoDBHashKey(attributeName = "con_id")
      @DynamoDBAutoGeneratedKey
      public String getConID(){
         return con_id;
      }
  
      public void setConID(String con_id){
         this.con_id = con_id;
      }
  }
  </code></pre>
  
  <p>Here I am receiving con_id value blank.</p>