com.expedia.graphql.hooks

Class DataFetcherExecutionPredicate

com.expedia.graphql.hooks.DataFetcherExecutionPredicate

public class DataFetcherExecutionPredicate

Perform runtime evaluations of each parameter passed to any KotlinDataFetcher.

The DataFetcherExecutionPredicate is declared globally for all the datafetchers instances and all the parameters. However a more precise logic (at the field level) is possible depending on the implement of evaluate and test

The predicate logic is split into two parts (evaluate and test) so the result of the evaluation like a list of errors can be passed to the onFailure method and added to an exception

Because the DataFetcherExecutionPredicate is global, it's not possible to have methods where the type is inferred.

It's recommended to check the type of the different arguments.

Constructor Summary

Constructors

Constructor and Description
DataFetcherExecutionPredicate() Perform runtime evaluations of each parameter passed to any KotlinDataFetcher.

Method Summary

Modifier and Type	Method and Description
<T> java.lang.Object	evaluate(T value, Parameter parameter, java.lang.String argumentName, graphql.schema.DataFetchingEnvironment environment) Evaluate if the value passed respects some constraints.
<T> T	execute(T value, Parameter parameter, java.lang.String argumentName, graphql.schema.DataFetchingEnvironment environment) Perform the predicate logic by evaluating the argument and its value Then depending on the result either returning the value itself to continue the datafetcher invocation or break the data fetching execution.
java.lang.Void	onFailure(java.lang.Object evaluationResult, Parameter parameter, java.lang.String argumentName, graphql.schema.DataFetchingEnvironment environment) If the test is unsuccessful, this function will be invoked.
boolean	test(java.lang.Object evaluationResult) Assert that the result of the {@link #evaluate(T, Parameter, String, DataFetchingEnvironment)} method is as expected eg: the list of errors is empty

Constructor Detail

DataFetcherExecutionPredicate

public DataFetcherExecutionPredicate()

Perform runtime evaluations of each parameter passed to any KotlinDataFetcher.

The DataFetcherExecutionPredicate is declared globally for all the datafetchers instances and all the parameters. However a more precise logic (at the field level) is possible depending on the implement of evaluate and test

The predicate logic is split into two parts (evaluate and test) so the result of the evaluation like a list of errors can be passed to the onFailure method and added to an exception

Because the DataFetcherExecutionPredicate is global, it's not possible to have methods where the type is inferred.

It's recommended to check the type of the different arguments.

Method Detail

execute

public <T> T execute(T value,
                     Parameter parameter,
                     java.lang.String argumentName,
                     graphql.schema.DataFetchingEnvironment environment)

Perform the predicate logic by evaluating the argument and its value Then depending on the result either returning the value itself to continue the datafetcher invocation or break the data fetching execution.

Parameters:

parameter - the function argument reference containing the KClass and the argument annotations

argumentName - the name of the argument as declared in the query / kotlin function

environment - the DataFetchingEnvironment in which the data fetcher is executed (gives access to field info, execution context etc)

value - the value to execute the predicate against.

evaluate

public <T> java.lang.Object evaluate(T value,
                                     Parameter parameter,
                                     java.lang.String argumentName,
                                     graphql.schema.DataFetchingEnvironment environment)

Evaluate if the value passed respects some constraints.

Parameters:

parameter - the function argument reference containing the KClass and the argument annotations

argumentName - the name of the argument as declared in the query / kotlin function

environment - the DataFetchingEnvironment in which the data fetcher is executed (gives access to field info, execution context etc)

value - the value to execute the predicate against.

Returns:

the result of the evaluation eg: List of errors

test

public boolean test(java.lang.Object evaluationResult)

Assert that the result of the {@link #evaluate(T, Parameter, String, DataFetchingEnvironment)} method is as expected eg: the list of errors is empty

Parameters:

evaluationResult - the result of the evaluation

Returns:

whether the parameter passes the predicate

onFailure

public java.lang.Void onFailure(java.lang.Object evaluationResult,
                                Parameter parameter,
                                java.lang.String argumentName,
                                graphql.schema.DataFetchingEnvironment environment)

If the test is unsuccessful, this function will be invoked.

An exception can then be thrown to block the data fetcher execution

Parameters:

evaluationResult - the object return by the evaluate function

parameter - the function argument reference containing the KClass and the argument annotations

argumentName - the name of the argument as declared in the query / kotlin function

environment - the DataFetchingEnvironment in which the data fetcher is executed (gives access to field info, execution context etc)