Package graphql.schema

Class SingletonPropertyDataFetcher<T>

java.lang.Object

graphql.schema.SingletonPropertyDataFetcher<T>

Type Parameters:

T - for two

All Implemented Interfaces:

DataFetcher<T>, LightDataFetcher<T>, TrivialDataFetcher<T>

public class SingletonPropertyDataFetcher<T>
extends java.lang.Object
implements LightDataFetcher<T>

The SingletonPropertyDataFetcher is much like the PropertyDataFetcher except that it is designed to only ever fetch properties via the name of the field passed in.

This uses the same code as PropertyDataFetcher and hence is also controlled by static methods such as PropertyDataFetcher.setUseNegativeCache(boolean)

Method Summary

Modifier and Type	Method	Description
T	get(DataFetchingEnvironment environment)	This is called by the graphql engine to fetch the value.
T	get(GraphQLFieldDefinition fieldDefinition, java.lang.Object sourceObject, java.util.function.Supplier<DataFetchingEnvironment> environmentSupplier)	This is called to by the engine to get a value from the source object in a lightweight fashion.
static LightDataFetcher<?>	singleton()	This returns the same singleton LightDataFetcher that fetches property values based on the name of the field that iis passed into it.
static DataFetcherFactory<?>	singletonFactory()	This returns the same singleton DataFetcherFactory that returns the value of singleton()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

singleton

public static LightDataFetcher<?> singleton()

This returns the same singleton LightDataFetcher that fetches property values based on the name of the field that iis passed into it.

Returns:

a singleton property data fetcher

singletonFactory

public static DataFetcherFactory<?> singletonFactory()

This returns the same singleton DataFetcherFactory that returns the value of singleton()

Returns:

a singleton data fetcher factory

get

public T get(GraphQLFieldDefinition fieldDefinition,
             java.lang.Object sourceObject,
             java.util.function.Supplier<DataFetchingEnvironment> environmentSupplier)
      throws java.lang.Exception

Description copied from interface: LightDataFetcher

This is called to by the engine to get a value from the source object in a lightweight fashion. Only the field and source object are passed in a materialised way. The more heavy weight DataFetchingEnvironment is wrapped in a supplier that is only created on demand.

If you are a lightweight data fetcher (like PropertyDataFetcher is) then you can implement this method to have a more lightweight method invocation. However, if you need field arguments etc. during fetching (most custom fetchers will) then you should use implement DataFetcher.get(DataFetchingEnvironment).

Specified by:

get in interface LightDataFetcher<T>

Parameters:

fieldDefinition - the graphql field definition

sourceObject - the source object to get a value from

environmentSupplier - a supplier of the DataFetchingEnvironment that creates it lazily

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.

get

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

Description copied from interface: DataFetcher

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 how to fetch a data value in graphql type terms.

Specified by:

get in interface DataFetcher<T>

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.