graphql.execution.batched

Annotation Type Batched

@Target(value=METHOD)
@Retention(value=RUNTIME)
public @interface Batched

When placed on DataFetcher.get(DataFetchingEnvironment), indicates that this DataFetcher is batched. This annotation must be used in conjunction with BatchedExecutionStrategy. Batching is valuable in many situations, such as when a DataFetcher must make a network or file system request.

When a DataFetcher is batched, the DataFetchingEnvironment.getSource() method is guaranteed to return a List. The DataFetcher.get(DataFetchingEnvironment) method MUST return a parallel List which is equivalent to running a DataFetcher over each input element individually.

Using the Batched annotation is equivalent to implementing BatchedDataFetcher instead of DataFetcher. It is preferred to use the Batched annotation.

For example, the following two DataFetcher objects are interchangeable if used with a BatchedExecutionStrategy.

 
 new DataFetcher() {
   @Override
   @Batched
   public Object get(DataFetchingEnvironment environment) {
     List<String> retVal = new ArrayList<>();
     for (String s: (List<String>) environment.getSource()) {}
       retVal.add(s + environment.getArgument("text"));
     
     return retVal;
   }
 }
 
 

 
 new DataFetcher() {
   @Override
   public Object get(DataFetchingEnvironment e) {
     return ((String)e.getSource()) + e.getArgument("text");
   }
 }