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bbakermanbbakerman
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A registry and a dispatcher for graphql
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‎build.gradle‎

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@@ -49,6 +49,7 @@ compileJava {
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}
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dependencies {
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compile "com.graphql-java:graphql-java:4.0"
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testCompile "junit:junit:$junitVersion"
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testCompile 'org.awaitility:awaitility:2.0.0'
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}

‎src/main/java/org/dataloader/DataLoaderRegistry.java‎

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package org.dataloader;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.concurrent.CopyOnWriteArrayList;
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/**
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* This allows data loaders to be registered together into a single place so
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* they can be dispatched as one.
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*/
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public class DataLoaderRegistry {
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private final List<DataLoader<?, ?>> dataLoaders = new CopyOnWriteArrayList<>();
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/**
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* @return the currently registered data loaders
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*/
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public List<DataLoader<?, ?>> getDataLoaders() {
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return new ArrayList<>(dataLoaders);
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}
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/**
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* This will register a new dataloader
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*
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* @param dataLoader the data loader to register
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*
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* @return this registry
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*/
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public DataLoaderRegistry register(DataLoader<?, ?> dataLoader) {
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if (!dataLoaders.contains(dataLoader)) {
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dataLoaders.add(dataLoader);
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}
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return this;
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}
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/**
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* This will unregister a new dataloader
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*
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* @param dataLoader the data loader to unregister
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*
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* @return this registry
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*/
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public DataLoaderRegistry unregister(DataLoader<?, ?> dataLoader) {
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dataLoaders.remove(dataLoader);
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return this;
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}
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/**
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* This will called {@link org.dataloader.DataLoader#dispatch()} on each of the registered
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* {@link org.dataloader.DataLoader}s
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*/
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public void dispatchAll() {
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dataLoaders.forEach(DataLoader::dispatch);
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}
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}

‎src/main/java/org/dataloader/graphql/DataLoaderDispatcherInstrumentation.java‎

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package org.dataloader.graphql;
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import graphql.ExecutionResult;
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import graphql.execution.instrumentation.InstrumentationContext;
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import graphql.execution.instrumentation.NoOpInstrumentation;
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import graphql.execution.instrumentation.parameters.InstrumentationExecutionStrategyParameters;
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import org.dataloader.DataLoaderRegistry;
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import java.util.concurrent.CompletableFuture;
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/**
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* This graphql {@link graphql.execution.instrumentation.Instrumentation} will dispatch
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* all the contained {@link org.dataloader.DataLoader}s when each level of the graphql
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* query is executed.
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*/
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public class DataLoaderDispatcherInstrumentation extends NoOpInstrumentation {
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private final DataLoaderRegistry dataLoaderRegistry;
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public DataLoaderDispatcherInstrumentation(DataLoaderRegistry dataLoaderRegistry) {
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this.dataLoaderRegistry = dataLoaderRegistry;
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}
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@Override
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public InstrumentationContext<CompletableFuture<ExecutionResult>> beginExecutionStrategy(InstrumentationExecutionStrategyParameters parameters) {
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return (result, t) -> dataLoaderRegistry.dispatchAll();
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}
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}

‎src/test/java/org/dataloader/DataLoaderRegistryTest.java‎

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package org.dataloader;
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import org.hamcrest.Matchers;
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import org.junit.Test;
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import java.util.concurrent.CompletableFuture;
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import static java.util.Arrays.asList;
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import static org.junit.Assert.assertThat;
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public class DataLoaderRegistryTest {
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final BatchLoader<Object, Object> identityBatchLoader = CompletableFuture::completedFuture;
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@Test
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public void registration_works() throws Exception {
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DataLoader<Object, Object> dlA = new DataLoader<>(identityBatchLoader);
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DataLoader<Object, Object> dlB = new DataLoader<>(identityBatchLoader);
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DataLoader<Object, Object> dlC = new DataLoader<>(identityBatchLoader);
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DataLoaderRegistry registry = new DataLoaderRegistry();
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registry.register(dlA).register(dlB).register(dlC);
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assertThat(registry.getDataLoaders(), Matchers.equalTo(asList(dlA, dlB, dlC)));
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// the same dl twice is one add
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registry = new DataLoaderRegistry();
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registry.register(dlA).register(dlB).register(dlC).register(dlA).register(dlB);
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assertThat(registry.getDataLoaders(), Matchers.equalTo(asList(dlA, dlB, dlC)));
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// and unregister
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registry.unregister(dlC);
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assertThat(registry.getDataLoaders(), Matchers.equalTo(asList(dlA, dlB)));
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}
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}

‎src/test/java/org/dataloader/graphql/DataLoaderDispatcherInstrumentationTest.java‎

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package org.dataloader.graphql;
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import graphql.ExecutionResult;
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import graphql.execution.instrumentation.InstrumentationContext;
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import org.dataloader.BatchLoader;
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import org.dataloader.DataLoader;
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import org.dataloader.DataLoaderRegistry;
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import org.junit.Test;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.concurrent.CompletableFuture;
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import java.util.concurrent.atomic.AtomicInteger;
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import static java.util.Arrays.asList;
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import static java.util.Collections.singletonList;
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import static org.hamcrest.Matchers.equalTo;
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import static org.junit.Assert.assertThat;
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public class DataLoaderDispatcherInstrumentationTest {
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@Test
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public void basic_invocation() throws Exception {
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AtomicInteger invocationCount = new AtomicInteger();
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final List<Object> loadedKeys = new ArrayList<>();
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final BatchLoader<Object, Object> identityBatchLoader = keys -> {
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invocationCount.incrementAndGet();
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loadedKeys.add(keys);
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return CompletableFuture.completedFuture(keys);
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};
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DataLoader<Object, Object> dlA = new DataLoader<>(identityBatchLoader);
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DataLoader<Object, Object> dlB = new DataLoader<>(identityBatchLoader);
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DataLoader<Object, Object> dlC = new DataLoader<>(identityBatchLoader);
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DataLoaderRegistry registry = new DataLoaderRegistry()
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.register(dlA)
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.register(dlB)
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.register(dlC);
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DataLoaderDispatcherInstrumentation dispatcher = new DataLoaderDispatcherInstrumentation(registry);
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InstrumentationContext<CompletableFuture<ExecutionResult>> context = dispatcher.beginExecutionStrategy(null);
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// cause some activity
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dlA.load("A");
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dlB.load("B");
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dlC.load("C");
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context.onEnd(null, null);
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assertThat(invocationCount.get(), equalTo(3));
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// will be [[A],[B],[C]]
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assertThat(loadedKeys, equalTo(asList(singletonList("A"), singletonList("B"), singletonList("C"))));
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}
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}

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