graphql.schema

Interface DataFetcher<T>

Type Parameters:

T - the type of object returned. May also be wrapped in a DataFetcherResult

All Known Subinterfaces:

BatchedDataFetcher

All Known Implementing Classes:

AsyncDataFetcher, PropertyDataFetcher, SimpleListConnection, StaticDataFetcher, UnbatchedDataFetcher

@PublicSpi
public interface DataFetcher<T>

A data fetcher is responsible for returning a data value back for a given graphql field. The graphql engine uses data fetchers to resolve / fetch a logical field into a runtime object that will be sent back as part of the overall graphql ExecutionResult In other implementations, these are sometimes called "Resolvers" or "Field Resolvers", because that is there function, they resolve a logical graphql field into an actual data value.

Method Summary

Modifier and Type	Method and Description
T	get(DataFetchingEnvironment environment) This is called by the graphql engine to fetch the value.
default boolean	isTrivialDataFetcher() If a data fetcher is simply mapping data from an object to a field, it can be considered a trivial data fetcher for the purposes of tracing and so on.

Method Detail

get

T get(DataFetchingEnvironment environment)
throws java.lang.Exception

This is called by the graphql engine to fetch the value. The DataFetchingEnvironment is a composite context object that tells you all you need to know about who to fetch a data value in graphql type terms.

Parameters:

environment - this is the data fetching environment which contains all the context you need to fetch a value

Returns:

a value of type T. May be wrapped in a DataFetcherResult

Throws:

java.lang.Exception - to relieve the implementations from having to wrap checked exceptions. Any exception thrown from a DataFetcher will eventually be handled by the registered DataFetcherExceptionHandler and the related field will have a value of null in the result.

isTrivialDataFetcher

default boolean isTrivialDataFetcher()

If a data fetcher is simply mapping data from an object to a field, it can be considered a trivial data fetcher for the purposes of tracing and so on.

Returns:

true if the data fetcher can be considered a trivial data fetcher.