GraphQL 与 Spring Boot 的初体验

GraphQL 既是一种用于 API 的查询语言也是一个满足你数据查询的运行时。 GraphQL 对你的 API 中的数据提供了一套易于理解的完整描述，使得客户端能够准确地获得它需要的数据，而且没有任何冗余，也让 API 更容易地随着时间推移而演进，还能用于构建强大的开发者工具。

定义 Schema

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# src/main/resources/schema.graphql
schema {
query: Query
}

type Query {
allBooks: [Book]
book(id: String): Book
}

type Book {
isbn: String
title: String
publisher: String
authors: [String]
publishedDate: String
}

加载并解析上面定义的 Schema

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@Service
public class GraphQLService {

@Value("classpath:schema.graphql")
private Resource resource;

@Getter
private GraphQL graphQL;
@Autowired
private AllBooksDataFetcher allBooksDataFetcher;
@Autowired
private BookDataFetcher bookDataFetcher;

@PostConstruct
private void loadSchema() throws IOException {
// 获取本地定义的 Schema 文件
File schemaFile = resource.getFile();
// 解析 Schema 文件
TypeDefinitionRegistry typeRegistry = new SchemaParser().parse(schemaFile);
RuntimeWiring wiring = buildRuntimeWiring();
GraphQLSchema schema = new SchemaGenerator().makeExecutableSchema(typeRegistry, wiring);
graphQL = GraphQL.newGraphQL(schema).build();
}

private RuntimeWiring buildRuntimeWiring() {
return RuntimeWiring.newRuntimeWiring()
.type("Query", typeWiring -> typeWiring
.dataFetcher("allBooks", allBooksDataFetcher)
.dataFetcher("book", bookDataFetcher)
).build();
}
}

提供 DataFetcher

相当于提供 Schema 中的 Query 实现：

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type Query {
allBooks: [Book]
book(id: String): Book
}

AllBooksDataFetcher 对应实现 allBooks: [Book]：

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@Component
public class AllBooksDataFetcher implements DataFetcher<List<Book>> {

@Autowired
private BookRepository bookRepository;

@Override
public List<Book> get(DataFetchingEnvironment dataFetchingEnvironment) {
return bookRepository.findAll();
}
}

BookDataFetcher 对应实现 book(id: String): Book：

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@Component
public class BookDataFetcher implements DataFetcher<Book> {

@Autowired
private BookRepository bookRepository;

@Override
public Book get(DataFetchingEnvironment dataFetchingEnvironment) {
String isn = dataFetchingEnvironment.getArgument("id");
return bookRepository.findById(isn).orElse(null);
}
}

提供 GraphQL API

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@RestController
@RequestMapping(path = "/v1/books")
public class BookController {

@Autowired
private GraphQLService graphQLService;

@PostMapping
public ResponseEntity<Object> getAllBooks(@RequestBody String query) {
ExecutionResult execute = graphQLService.getGraphQL().execute(query);
return new ResponseEntity<>(execute, HttpStatus.OK);
}
}

启动并测试

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$ mvn install
...
[INFO] BUILD SUCCESS
...
$ mvn spring-boot:run
...
2019-08-24 19:35:11.700 INFO 14464 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2019-08-24 19:35:11.702 INFO 14464 --- [ main] i.g.y.s.graphql.GraphQLApplication : Started GraphQLApplication in 16.808 seconds (JVM running for 25.601)

查询部分字段

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$ curl -X POST \
http://127.0.0.1:8080/v1/books \
-H 'Content-Type: text/plain' \
-d '{
allBooks {
isbn
title
}
}' | jq
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 579 0 524 100 55 34933 3666 --:--:-- --:--:-- --:--:-- 38600
{
"errors": [],
"data": {
"allBooks": [
{
"isbn": "9787111213826",
"title": "Java 编程思想（第4版）"
},
...
]
},
"extensions": null,
"dataPresent": true
}

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$ curl -X POST \
http://127.0.0.1:8080/v1/books \
-H 'Content-Type: text/plain' \
-d '{
book(id: "9787121362132") {
title
}
}' | jq
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 210 0 159 100 51 1691 542 --:--:-- --:--:-- --:--:-- 2234
{
"errors": [],
"data": {
"book": {
"title": "高可用可伸缩微服务架构：基于 Dubbo、Spring Cloud 和 Service Mesh"
}
},
"extensions": null,
"dataPresent": true
}

查询全部字段

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$ curl -X POST \
http://127.0.0.1:8080/v1/books \
-H 'Content-Type: text/plain' \
-d '{
allBooks {
isbn
title
authors
publisher
publishedDate
}
}' | jq
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 1139 0 1044 100 95 750 68 0:00:01 0:00:01 --:--:-- 818
{
"errors": [],
"data": {
"allBooks": [
{
"isbn": "9787111213826",
"title": "Java 编程思想（第4版）",
"authors": [
"Bruce Eckel"
],
"publisher": "机械工业出版社",
"publishedDate": "2007-06-01"
},
...
]
},
"extensions": null,
"dataPresent": true
}

Copy
$ curl -X POST \
http://127.0.0.1:8080/v1/books \
-H 'Content-Type: text/plain' \
-d '{
book(id: "9787121362132") {
title
authors
publisher
publishedDate
}
}' | jq
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 421 0 320 100 101 312k 98k --:--:-- --:--:-- --:--:-- 411k
{
"errors": [],
"data": {
"book": {
"title": "高可用可伸缩微服务架构：基于 Dubbo、Spring Cloud 和 Service Mesh",
"authors": [
"程超",
"梁桂钊",
"秦金卫",
"方志斌",
"张逸",
"杜琪",
"殷琦",
"肖冠宇"
],
"publisher": "电子工业出版社",
"publishedDate": "2019-05-01"
}
},
"extensions": null,
"dataPresent": true
}

查询多个数据

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$ curl -X POST \
http://127.0.0.1:8080/v1/books \
-H 'Content-Type: text/plain' \
-d '{
allBooks {
isbn
title
}
book(id: "9787121362132") {
title
authors
publisher
publishedDate
}
}' | jq
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 930 0 785 100 145 3866 714 --:--:-- --:--:-- --:--:-- 4581
{
"errors": [],
"data": {
"allBooks": [
{
"isbn": "9787111213826",
"title": "Java 编程思想（第4版）"
},
{
"isbn": "9787111421900",
"title": "深入理解 Java 虚拟机：JVM 高级特性与最佳实践（第2版）"
},
{
"isbn": "9787115221704",
"title": "重构 改善既有代码的设计（第2版）"
},
{
"isbn": "9787121362132",
"title": "高可用可伸缩微服务架构：基于 Dubbo、Spring Cloud 和 Service Mesh"
},
{
"isbn": "9787302392644",
"title": "人月神话（40周年中文纪念版）"
}
],
"book": {
"title": "高可用可伸缩微服务架构：基于 Dubbo、Spring Cloud 和 Service Mesh",
"authors": [
"程超",
"梁桂钊",
"秦金卫",
"方志斌",
"张逸",
"杜琪",
"殷琦",
"肖冠宇"
],
"publisher": "电子工业出版社",
"publishedDate": "2019-05-01"
}
},
"extensions": null,
"dataPresent": true
}

综上可见，API 不变只改动了查询的内容，就会自动响应不同的结果。

参考链接

https://graphql.org/

https://developer.github.com/v4/

https://www.baeldung.com/graphql

https://www.baeldung.com/spring-graphql

https://youtu.be/zX2I7-aIldE

https://leader.js.cool/#/basic/db/graphql

https://github.com/glennreyes/graphpack

全面解析 GraphQL，携程微服务背景下的前后端数据交互方案

前端 er 了解 GraphQL，看这篇就够了

GraphQL 之路

谈谈 GraphQL 的历史、组件和生态系统