graphql java demo_GraphQL学习，Java简单实现

简介

是一种查询语言，类似前端与后端之间通过sql语言进行交互。用类似json的语言来查询需要的数据。

如在以下查询语句

{

bookById(id: "1") {

id

name

pageCount

author {

name

}

}

}

可以得到一下结果

{

"data": {

"bookById": {

"id": "1",

"name": "风雪追击",

"pageCount": 233,

"author": {

"name": "东野圭吾"

}

}

}

}

maven依赖

org.springframework.boot

spring-boot-starter

org.springframework.boot

spring-boot-starter-web

com.graphql-java

graphql-java

11.0

com.graphql-java

graphql-java-spring-boot-starter-webmvc

1.0

com.google.guava

guava

26.0-jre

定义schema

上面的查询语句我们事先定义了一下schema,放置在src/main/resources/schema.graphqls

type Query {

bookById(id: ID): Book

authors:[Author]

books:[Book]

authorAndBooks:[Author]

}

type Book {

id: ID

name: String

pageCount: Int

author: Author

}

type Author {

id: ID

name: String

books:[Book]

}

其中类型为Query的表示为查询，类似CURD中的R；除了Query还有Mutation来表示对数据进行修改，相当于CURD中的CUD操作。在schema中定义了4跳query语句如上所示。我们还定义了Book和Author的类型，其中Book中包含一个Author，Author中包含Book的列表。

定义GraphQLProvider

GraphQLProvider类将会创建一个GraphQL的实例，这里通过@Bean的方式暴露出去可以通过/graphql的url访问到(由依赖graphql-java-spring-boot-starter-webmvc实现的功能)

@Component

public class GraphQLProvider {

private GraphQL graphQL;

@Bean

public GraphQL graphQL() {

return graphQL;

}

@Autowired

GraphQLDataFetchers graphQLDataFetchers;

@PostConstruct

public void init() throws IOException {

URL url = Resources.getResource("schema.graphqls");

String sdl = Resources.toString(url, Charsets.UTF_8);

GraphQLSchema graphQLSchema = buildSchema(sdl);

this.graphQL = GraphQL.newGraphQL(graphQLSchema).build();

}

private GraphQLSchema buildSchema(String sdl) {

TypeDefinitionRegistry typeRegistry = new SchemaParser().parse(sdl);

RuntimeWiring runtimeWiring = buildWiring();

SchemaGenerator schemaGenerator = new SchemaGenerator();

return schemaGenerator.makeExecutableSchema(typeRegistry, runtimeWiring);

}

private RuntimeWiring buildWiring() {

Map map = new HashMap();

map.put("bookById",graphQLDataFetchers.getBookByIdDataFetcher());

map.put("books",graphQLDataFetchers.getBooksDataFetcher());

map.put("authors",graphQLDataFetchers.getAuthorsDataFetcher());

return RuntimeWiring.newRuntimeWiring()

.type(newTypeWiring("Query")

.dataFetchers(map))

.type(newTypeWiring("Book")

.dataFetcher("author", graphQLDataFetchers.getAuthorDataFetcher())

.dataFetcher("pageCount",graphQLDataFetchers.getPageCountDataFetcher()))

.type(newTypeWiring("Author")

.dataFetcher("books",graphQLDataFetchers.getBooksByAUthorDataFetcher()))

.build();

}

}

DataFetchers

GraphQL在执行查询时，是通过Datafetcher来获取一个字段的数据。DataFetcher是一个接口

public interface DataFetcher {

T get(DataFetchingEnvironment var1) throws Exception;

}

新建一个类用于存放所有的datafetcher(小型项目)

@Component

public class GraphQLDataFetchers {

private static List> books = Arrays.asList(

ImmutableMap.of("id", "1",

"name", "风雪追击",

"totalPages", "233",

"authorId", "a1"),

ImmutableMap.of("id", "4",

"name", "解忧杂货店",

"totalPages", "342",

"authorId", "a1"),

ImmutableMap.of("id", "2",

"name", "达芬奇密码",

"totalPages", "635",

"authorId", "a2"),

ImmutableMap.of("id", "3",

"name", "大秦帝国",

"totalPages", "371",

"authorId", "a3")

);

private static List> authors = Arrays.asList(

ImmutableMap.of("id", "a1",

"name", "东野圭吾"),

ImmutableMap.of("id", "a2",

"name", "丹布朗"),

ImmutableMap.of("id", "a3",

"name", "孙皓晖")

);

public DataFetcher getBookByIdDataFetcher() {

return dataFetchingEnvironment -> {

String bookId = dataFetchingEnvironment.getArgument("id");

return books

.stream()

.filter(book -> book.get("id").equals(bookId))

.findFirst()

.orElse(null);

};

}

public DataFetcher getAuthorDataFetcher() {

return dataFetchingEnvironment -> {

Map book = dataFetchingEnvironment.getSource();

String authorId = book.get("authorId");

return authors

.stream()

.filter(author -> author.get("id").equals(authorId))

.findFirst()

.orElse(null);

};

}

public DataFetcher getBooksByAUthorDataFetcher(){

return dataFetchingEnvironment -> {

Map author = dataFetchingEnvironment.getSource();

String authorId = author.get("id");

return books.stream().filter(book->book.get("authorId").equals(authorId)).toArray();

};

}

public DataFetcher getAuthorTotalCountDataFetcher(){

return dataFetchingEnvironment -> {

Map author = dataFetchingEnvironment.getSource();

String authorId = author.get("id").toString();

return books.stream().filter(book->book.get("authorId").equals(authorId))

.collect(Collectors.summingInt(map->Integer.parseInt(map.get("totalPages"))));

};

}

public DataFetcher getAuthorsDataFetcher(){

return dataFetchingEnvironment->{

return authors;

};

}

public DataFetcher getBooksDataFetcher(){

return dataFetchingEnvironment -> {

return books;

};

}

public DataFetcher getPageCountDataFetcher() {

return dataFetchingEnvironment -> {

Map book = dataFetchingEnvironment.getSource();

return book.get("totalPages");

};

}

}

验证

可以使用graphql-playground工具来进行验证。我电脑的版本是macos10.15.4，使用1.8.9可以运行，1.8.10则会报错，使用前需要在顶栏输入http://localhost:8080/graphql,然后在左边输入查询语句，右边就能得到查询结果。

image.png

参考链接