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smallrye#521: implement federation data fetcher and type resolver
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server/implementation/src/main/java/io/smallrye/graphql/bootstrap/FederationDataFetcher.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| package io.smallrye.graphql.bootstrap; | ||
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| import static java.util.stream.Collectors.toList; | ||
| import static java.util.stream.Collectors.toSet; | ||
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| import java.util.HashMap; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Set; | ||
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| import com.apollographql.federation.graphqljava._Entity; | ||
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| import graphql.schema.DataFetcher; | ||
| import graphql.schema.DataFetchingEnvironment; | ||
| import graphql.schema.DelegatingDataFetchingEnvironment; | ||
| import graphql.schema.GraphQLArgument; | ||
| import graphql.schema.GraphQLCodeRegistry; | ||
| import graphql.schema.GraphQLFieldDefinition; | ||
| import graphql.schema.GraphQLObjectType; | ||
| import graphql.schema.GraphQLOutputType; | ||
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| class FederationDataFetcher implements DataFetcher<List<Object>> { | ||
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| private final GraphQLObjectType queryType; | ||
| private final GraphQLCodeRegistry codeRegistry; | ||
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| public FederationDataFetcher(GraphQLObjectType queryType, GraphQLCodeRegistry codeRegistry) { | ||
| this.queryType = queryType; | ||
| this.codeRegistry = codeRegistry; | ||
| } | ||
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| @Override | ||
| public List<Object> get(DataFetchingEnvironment environment) throws Exception { | ||
| return environment.<List<Map<String, Object>>> getArgument(_Entity.argumentName).stream() | ||
| .map(representations -> fetchEntities(environment, representations)) | ||
| .collect(toList()); | ||
| } | ||
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| private Object fetchEntities(DataFetchingEnvironment env, Map<String, Object> representations) { | ||
| Map<String, Object> requestedArgs = new HashMap<>(representations); | ||
| requestedArgs.remove("__typename"); | ||
| String typename = (String) representations.get("__typename"); | ||
| for (GraphQLFieldDefinition field : queryType.getFields()) { | ||
| if (matchesReturnType(field, typename) && matchesArguments(requestedArgs, field)) { | ||
| return execute(field, env, requestedArgs); | ||
| } | ||
| } | ||
| throw new RuntimeException("no query found for " + typename + " by " + requestedArgs.keySet()); | ||
| } | ||
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| private boolean matchesReturnType(GraphQLFieldDefinition field, String typename) { | ||
| GraphQLOutputType returnType = field.getType(); | ||
| return returnType instanceof GraphQLObjectType && ((GraphQLObjectType) returnType).getName().equals(typename); | ||
| } | ||
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| private boolean matchesArguments(Map<String, Object> requestedArguments, GraphQLFieldDefinition field) { | ||
| Set<String> argumentNames = field.getArguments().stream().map(GraphQLArgument::getName).collect(toSet()); | ||
| return argumentNames.equals(requestedArguments.keySet()); | ||
| } | ||
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| private Object execute(GraphQLFieldDefinition field, DataFetchingEnvironment env, Map<String, Object> requestedArgs) { | ||
| DataFetcher<?> dataFetcher = codeRegistry.getDataFetcher(queryType, field); | ||
| DataFetchingEnvironment argsEnv = new DelegatingDataFetchingEnvironment(env) { | ||
| @Override | ||
| public Map<String, Object> getArguments() { | ||
| return requestedArgs; | ||
| } | ||
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| @Override | ||
| public boolean containsArgument(String name) { | ||
| return requestedArgs.containsKey(name); | ||
| } | ||
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| @Override | ||
| public <T> T getArgument(String name) { | ||
| //noinspection unchecked | ||
| return (T) requestedArgs.get(name); | ||
| } | ||
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| @Override | ||
| public <T> T getArgumentOrDefault(String name, T defaultValue) { | ||
| return containsArgument(name) ? getArgument(name) : defaultValue; | ||
| } | ||
| }; | ||
| try { | ||
| return dataFetcher.get(argsEnv); | ||
| } catch (Exception e) { | ||
| throw new RuntimeException("can't fetch data from " + field, e); | ||
| } | ||
| } | ||
| } |