GraphQL接口查询语言初步学习

A query language for your API

最近公司经常用到这东西&＃xff0c;小编出于兴趣&＃xff0c;学习一二&＃xff0c;记录如下&＃xff0c;如有不妥&＃xff0c;还望多多指教。

一 概述

GraphQL是一种用于api的查询语言&＃xff0c;在项目运行时对现有数据的一种查询方式。GraphQL为API中的数据提供了一个完整的、可理解的描述&＃xff0c;允许客户端要求他们真正需要的东西&＃xff0c;使API更容易随着时间的推移而发展&＃xff0c;并支持强大的开发工具。

同级可对比APIJson,个人感觉apiJson在Java开发中比较实用和简单&＃xff0c;如权限验证通过 &＃64; MethodAccess 注解Model来添加角色对表的操作权限&＃xff0c;以及支持远程函数调用&＃xff0c;而相对比&＃xff0c;graphql学习难度和成本以及规范性&＃xff0c;都比较高。不过技多不压身&＃xff0c;今天咱来看看。
&＃xff08;APIjson个人感觉可参考该博客&＃xff0c;感觉还不错https://blog.csdn.net/u014618954/article/details/107021638/&＃xff09;

二 初步展示

graphql是api的查询语言&＃xff0c;在一定程度上使开发更加高效和便捷&＃xff0c;一下是一个例子。
例如&＃xff0c;一个GraphQL服务告诉我们登录用户是谁(me)以及该用户的名字可能是这样的:
①创建
在这些类型上定义类型和字段&＃xff0c;然后为每种类型的每个字段提供函数。

type Query {me: User
}type User {id: IDname: String
}


function Query_me(request) {return request.auth.user;
}function User_name(user) {return user.getName();
}


②查询

{me {name}
}


③返回

{"me": {"name": "Luke Skywalker"}
}


上述为查询query,可根据name查询所有对应名字的name,以及通过type,多参等查询优点&＃xff0c;具体也不多说&＃xff0c;可参考graphql官方文档&＃xff0c;简单讲解分为三点&＃xff0c;如下。

应用场景&＃xff1a;
①多平台等原因导致的字段冗余
②一个页面多次调用聚合数据
③经常改动接口且精简逻辑

三 实际应用

讲了半天湿的&＃xff0c;下面来点干货&＃xff0c;本次演示Java和go两种语言的基本使用

3.1 java&＃43;spring boot&＃43;graphql

我们的示例应用程序将是一个简单的API&＃xff0c;用于获取特定书籍的详细信息。

① 构建目录

Select:Gradle ProjectJavaSpring Boot 2.1.x
Project metadataGroup: com.graphql-java.tutorialArtifact: book-details
Dependencyweb


② 添加基础依赖


com.graphql-java:graphql-java:11.0 // NEW
com.graphql-java:graphql-java-spring-boot-starter-webmvc:1.0 // NEW
com.google.guava:guava:26.0-jre // NEW
org.springframework.boot:spring-boot-starter-web
org.springframework.boot:spring-boot-starter-test
}


③ 创建相关文件
在src/main/resources目录下创建 schema.graphqls

//该部分是一个关于书籍的基本类型的定义&＃xff0c;并与后续类型的查询有关
type Query {bookById(id: ID): Book
}type Book {id: IDname: StringpageCount: Intauthor: Author
}type Author {id: IDfirstName: StringlastName: String
}


在com.graphqljava.tutorial.bookdetails目录下创建GraphQLProvider.class,并创建一个GraphQL实例&＃xff1a;

&＃64;Component
public class GraphQLProvider {private GraphQL graphQL;&＃64;Beanpublic GraphQL graphQL() { return graphQL;// 这个GraphQL实例通过使用&＃64;Bean注释的GraphQL()方法公开为一个Spring Bean}&＃64;PostConstructpublic void init() throws IOException {//使用Guava资源从类路径读取文件URL url &＃61; Resources.getResource("schema.graphqls");//GraphQL Java Spring适配器将使用该GraphQL实例使我们的模式通过HTTP在默认url / String sdl &＃61; Resources.toString(url, Charsets.UTF_8);//创建一个GraphQLSchema和GraphQL实例GraphQLSchema graphQLSchema &＃61; buildSchema(sdl);this.graphQL &＃61; GraphQL.newGraphQL(graphQLSchema).build();}&＃64;AutowiredGraphQLDataFetchers graphQLDataFetchers;//抓取数据private GraphQLSchema buildSchema(String sdl) {TypeDefinitionRegistry typeRegistry &＃61; new SchemaParser().parse(sdl);RuntimeWiring runtimeWiring &＃61; buildWiring();SchemaGenerator schemaGenerator &＃61; new SchemaGenerator();return schemaGenerator.makeExecutableSchema(typeRegistry, runtimeWiring);}/*buildWiring使用graphQLDataFetchers bean实际注册两个DataFetchers:一个用于检索具有特定ID的图书一个用于获取特定书籍的作者*/private RuntimeWiring buildWiring() {return RuntimeWiring.newRuntimeWiring().type(newTypeWiring("Query").dataFetcher("bookById", graphQLDataFetchers.getBookByIdDataFetcher())).type(newTypeWiring("Book").dataFetcher("author", graphQLDataFetchers.getAuthorDataFetcher())).build();}
}

重要的接口&＃xff08;不用自己创&＃xff09;&＃xff1a;
DataFetcher是一个带有单个方法的接口&＃xff0c;它只接受DataFetcherEnvironment类型的单个参数&＃xff1b;
当GraphQL Java执行查询时&＃xff0c;它会为在查询中遇到的每个字段调用适当的数据表器。

public interface DataFetcher {T get(DataFetchingEnvironment dataFetchingEnvironment) throws Exception;
}


让我们假设有一个不匹配的图书映射有一个关键totalPages而不是pageCount。这将导致每本书的pageCount值为空&＃xff0c;因为PropertyDataFetcher无法获取正确的值。为了解决这个问题&＃xff0c;你必须为Book注册一个新的DataFetcher&＃xff08;本文案例不需要&＃xff09;

// 在 GraphQLDataFetchers class// 实现 DataFetcherpublic DataFetcher getPageCountDataFetcher() {return dataFetchingEnvironment -> {Map book &＃61; dataFetchingEnvironment.getSource();return book.get("totalPages");};}


创建一个新的类GraphQLDataFetchers&＃xff0c;其中包含书籍和作者的示例列表

&＃64;Component
public class GraphQLDataFetchers {private static List> books &＃61; Arrays.asList(ImmutableMap.of("id", "book-1","name", "Harry Potter and the Philosopher&＃39;s Stone","pageCount", "223","authorId", "author-1"),ImmutableMap.of("id", "book-2","name", "Moby Dick","pageCount", "635","authorId", "author-2"),ImmutableMap.of("id", "book-3","name", "Interview with the vampire","pageCount", "371","authorId", "author-3"));private static List> authors &＃61; Arrays.asList(ImmutableMap.of("id", "author-1","firstName", "Joanne","lastName", "Rowling"),ImmutableMap.of("id", "author-2","firstName", "Herman","lastName", "Melville"),ImmutableMap.of("id", "author-3","firstName", "Anne","lastName", "Rice"));public DataFetcher getBookByIdDataFetcher() {return dataFetchingEnvironment -> {String bookId &＃61; dataFetchingEnvironment.getArgument("id");return books.stream().filter(book -> book.get("id").equals(bookId)).findFirst().orElse(null);};}public DataFetcher getAuthorDataFetcher() {return dataFetchingEnvironment -> {Map book &＃61; dataFetchingEnvironment.getSource();String authorId &＃61; book.get("authorId");return authors.stream().filter(author -> author.get("id").equals(authorId)).findFirst().orElse(null);};}
}


加入application的main方法启动项目测试

package com.graphqljava.tutorial.bookdetails;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;&＃64;SpringBootApplication
public class BookDetailsApplication {public static void main(String[] args) {SpringApplication.run(BookDetailsApplication.class, args);}}


可通过网页版测试https://cpq-dev.ext.hp.com/playground

可以很清晰的拿到结果了
&＃xff08;该playground可自行安装相应测试软件&＃xff0c;如postman,altair,本文使用网页版&＃xff0c;如有问题可参考源码&＃xff1a;https://github.com/graphql-java/tutorials&＃xff09;

3.2 Golang&＃43;graphql

① 安装相应支持

go get github.com/graphql-go/graphql


&＃xff08;此目录为path目录下&＃xff0c;之前博客有讲导包问题&＃xff0c;可前往浏览&＃xff0c;如不知道自己项目path目录&＃xff0c;可用 go Current GOPATH 命令查找&＃xff09;

② 应用举例
下面是一个简单的例子&＃xff0c;它定义了一个带有hello字符串类型字段的模式和一个返回字符串世界的Resolve方法。对该模式执行GraphQL查询&＃xff0c;结果输出以JSON格式打印

package mainimport ("encoding/json""fmt""log""github.com/graphql-go/graphql"
)func main() {// Schemafields :&＃61; graphql.Fields{"hello": &graphql.Field{Type: graphql.String,Resolve: func(p graphql.ResolveParams) (interface{}, error) {return "world", nil},},}rootQuery :&＃61; graphql.ObjectConfig{Name: "RootQuery", Fields: fields}schemaConfig :&＃61; graphql.SchemaConfig{Query: graphql.NewObject(rootQuery)}schema, err :&＃61; graphql.NewSchema(schemaConfig)if err !&＃61; nil {log.Fatalf("failed to create new schema, error: %v", err)}// Queryquery :&＃61; &＃96;{hello}&＃96;params :&＃61; graphql.Params{Schema: schema, RequestString: query}r :&＃61; graphql.Do(params)if len(r.Errors) > 0 {log.Fatalf("failed to execute graphql operation, errors: %&＃43;v", r.Errors)}rJSON, _ :&＃61; json.Marshal(r)fmt.Printf("%s \n", rJSON) // {"data":{"hello":"world"}}
}


上述为简单示例&＃xff0c;更多有趣复杂案例推荐可前往
https://github.com/graphql-go/graphql/tree/master/examples/
https://github.com/graphql-go/graphql/blob/master/graphql_test.go 学习

本人也是对graphql初步学习&＃xff0c;也希望大佬多多提建议

本文参考学习于
https://graphql.org/官网及相关git源码

个人推荐https://blog.csdn.net/qq_41882147/article/details/82966783&＃xff0c;挺详细&＃xff0c;介绍也比较实际&＃xff0c;可适合进阶学习