JSON

Another way of assembling applications without writing Java code is through JSON.

This format can be created manually, but it could also be used to generate the DAG from a different frontend, like a visual tool. Here is the word count written in JSON:

{ 
   "displayName": "WordCountJSON",
   "operators": [ 
   { "name": "input", ... }, { "name": "parse", ... },
   { 
      "name": "count",
      "class": "com.datatorrent.lib.algo.UniqueCounter",
       "properties": { "com.datatorrent.lib.algo.UniqueCounter": { "cumulative": 
         false } } 
   }, 
   { "name": "console", ... } ],
   "streams": [ 
   { "name": "lines", 
     "sinks": [ { "operatorName": "parse", "portName": "input" } ],
     "source": { "operatorName": "input", "portName": "output" } 
   }, 
   { "name": "words", ... },
   { "name": "counts", ... } 
   ] 
 } 

Just like applications that are written in Java, the JSON files will be included in the application package, along with the operator dependencies. Upon launch of the application, the Apex client will parse these files and translate them into a native DAG representation.