GraphQL--springBoot java demo

GraphQL is a query language :

搭建server， 供前端与后端使用的时候 参考：howtoGraphQL
简单的语法学习： learn

GraphQL 是一个新的API标准， 可以比Rest更有效的 强大的 灵活；它是由FaceBook开发并开源
API defines how a clientcan load data from a server.
Graph QL是一种都API的查询语言， 不是数据库查询语言， 比Rest更优越

GraphiQL An in-browser IDE for exploring GraphQL.

自己创建参看： readme

简单的搭建一个自己的server

参考 Getting started with GraphQL Java and Spring Boot

1. 安装Java： download JDK1.8， 然后安装JDK与JRE， 配置环境变量
2. 安装Gradle： download zip文件， 解压到相关路径， 并配置环境变量； 参考install
   显示如下便成功了：

gradle -v

Welcome to Gradle 5.6!

3. 按照文档中的示例， 创建spring app： https://start.spring.io/.
   选择
   --Gradle Project
   --Java
   --Spring Boot 2.1.x
   --Group: com.graphql-java.tutorial
   --Artifact: book-details
   -- select Web.这个我自己选择的是

4. 点击后， 会生成一个项目文件的压缩包， 直接解压到电脑中， 然后倒入Idea IDE， 注意导入后， 自己去seeting中设置JDK与Gradle为自己电脑上安装的location
5. 粘贴文档中的代码 作者放在了github中
6. build 项目

代码分析

报错了：

在浏览器中输入： http://localhost:8080/graphql
显示的结果是：

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

Tue Aug 27 14:59:09 CST 2019
There was an unexpected error (type=Bad Request, status=400).
Required String parameter 'query' is not present

在idea中显示如下：

"D:\Install\IdeaUI\IntelliJ IDEA 2019.2.1\jbr\bin\java.exe" -XX:TieredStopAtLevel=1 -noverify -Dspring.output.ansi.enabled=always -Dcom.sun.management.jmxremote -Dspring.jmx.enabled=true -Dspring.liveBeansView.mbeanDomain -Dspring.application.admin.enabled=true "-javaagent:D:\Install\IdeaUI\IntelliJ IDEA 2019.2.1\lib\idea_rt.jar=59523:D:\Install\IdeaUI\IntelliJ IDEA 2019.2.1\bin" -Dfile.encoding=UTF-8 -classpath D:\springBoot\book-details\build\classes\java\main;D:\springBoot\book-details\build\resources\main;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot-starter-web\2.1.7.RELEASE\fa43baf40bde3ecdb93ac9c545dd39f82ab29c35\spring-boot-starter-web-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.session\spring-session-core\2.1.8.RELEASE\2fe4df49293b18373c1050649192ff444be65f6\spring-session-core-2.1.8.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.graphql-java\graphql-java-spring-boot-starter-webmvc\1.0\4cf4fe366b11da5db76127a6b0607909b16977c5\graphql-java-spring-boot-starter-webmvc-1.0.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.graphql-java\graphql-java-spring-webmvc\1.0\93bd3420e9fd1c9e03cf2de0f438f9da2af923b4\graphql-java-spring-webmvc-1.0.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.graphql-java\graphql-java\11.0\1f670532643686b9816a871e2c9b9e5dce205eb6\graphql-java-11.0.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.google.guava\guava\26.0-jre\6a806eff209f36f635f943e16d97491f00f6bfab\guava-26.0-jre.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot-starter-json\2.1.7.RELEASE\9c12f046a7c4ae110d89163a491ad0d7cf036e79\spring-boot-starter-json-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot-starter\2.1.7.RELEASE\e23f4e9460e0e2220b444e40fc7fd6e95f66e0fe\spring-boot-starter-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot-starter-tomcat\2.1.7.RELEASE\11f2a86aefefba72a4efe5ff18f4165a4b4e78b\spring-boot-starter-tomcat-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.hibernate.validator\hibernate-validator\6.0.17.Final\af73055fc4a103ab347c56e7da5a143d68a0170\hibernate-validator-6.0.17.Final.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-webmvc\5.1.9.RELEASE\b9d4a2140488f0e6f9aa231e7938ae18da77b637\spring-webmvc-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-web\5.1.9.RELEASE\9fe4390420fdd0b63dc4ed90d9027dafa9f74f80\spring-web-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot-autoconfigure\2.1.7.RELEASE\2c9d3e2c6ea3cb435e99e2973009636b62a9d816\spring-boot-autoconfigure-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot\2.1.7.RELEASE\1599a2ad1fc6d36dbfc2a7c0dd5dab3a0bb27c61\spring-boot-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-context\5.1.9.RELEASE\c37f8fe15a5ae4ea1f351bd46167fd492a84eefa\spring-context-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-aop\5.1.9.RELEASE\bc2312ffad02251b9d472e4a7c0e472a58f50fbf\spring-aop-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-beans\5.1.9.RELEASE\5a03b3983108d73978aec2fa3e681aedad6782c\spring-beans-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-expression\5.1.9.RELEASE\db3a2468c1b7d697ec3b3ec6e5652dc282994fe3\spring-expression-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-core\5.1.9.RELEASE\dc3815439579b4fa0c19970e6b8e5d774af8d988\spring-core-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework\spring-jcl\5.1.9.RELEASE\7c372790c999777d20f364960cf557dd74f890cf\spring-jcl-5.1.9.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.antlr\antlr4-runtime\4.7.1\946f8aa9daa917dd81a8b818111bec7e288f821a\antlr4-runtime-4.7.1.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.springframework.boot\spring-boot-starter-logging\2.1.7.RELEASE\6e829f739992a7f368c0af44a08ed89ad2a1972f\spring-boot-starter-logging-2.1.7.RELEASE.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\ch.qos.logback\logback-classic\1.2.3\7c4f3c474fb2c041d8028740440937705ebb473a\logback-classic-1.2.3.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.apache.logging.log4j\log4j-to-slf4j\2.11.2\6d37bf7b046c0ce2669f26b99365a2cfa45c4c18\log4j-to-slf4j-2.11.2.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.slf4j\jul-to-slf4j\1.7.26\8031352b2bb0a49e67818bf04c027aa92e645d5c\jul-to-slf4j-1.7.26.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.slf4j\slf4j-api\1.7.26\77100a62c2e6f04b53977b9f541044d7d722693d\slf4j-api-1.7.26.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.graphql-java\java-dataloader\2.1.1\2ac1e4f0764030853195bf89eb4bd0bbe2151eb2\java-dataloader-2.1.1.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.reactivestreams\reactive-streams\1.0.2\323964c36556eb0e6209f65c1cef72b53b461ab8\reactive-streams-1.0.2.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.google.code.findbugs\jsr305\3.0.2\25ea2e8b0c338a877313bd4672d3fe056ea78f0d\jsr305-3.0.2.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.checkerframework\checker-qual\2.5.2\cea74543d5904a30861a61b4643a5f2bb372efc4\checker-qual-2.5.2.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.google.errorprone\error_prone_annotations\2.1.3\39b109f2cd352b2d71b52a3b5a1a9850e1dc304b\error_prone_annotations-2.1.3.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.google.j2objc\j2objc-annotations\1.1\ed28ded51a8b1c6b112568def5f4b455e6809019\j2objc-annotations-1.1.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.codehaus.mojo\animal-sniffer-annotations\1.14\775b7e22fb10026eed3f86e8dc556dfafe35f2d5\animal-sniffer-annotations-1.14.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\javax.annotation\javax.annotation-api\1.3.2\934c04d3cfef185a8008e7bf34331b79730a9d43\javax.annotation-api-1.3.2.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml.jackson.datatype\jackson-datatype-jdk8\2.9.9\4b04126963103216c9c43b0f34bbc36315654204\jackson-datatype-jdk8-2.9.9.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml.jackson.datatype\jackson-datatype-jsr310\2.9.9\a33df137557793b0404a486888dbe049f7abeeeb\jackson-datatype-jsr310-2.9.9.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml.jackson.module\jackson-module-parameter-names\2.9.9\a92facb55a2538e7b2fe14294570a18b823ad431\jackson-module-parameter-names-2.9.9.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.yaml\snakeyaml\1.23\ec62d74fe50689c28c0ff5b35d3aebcaa8b5be68\snakeyaml-1.23.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml.jackson.core\jackson-databind\2.9.9\d6eb9817d9c7289a91f043ac5ee02a6b3cc86238\jackson-databind-2.9.9.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.apache.tomcat.embed\tomcat-embed-websocket\9.0.22\45974d3443cc15ad9d10239d762d5e15759e6364\tomcat-embed-websocket-9.0.22.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.apache.tomcat.embed\tomcat-embed-core\9.0.22\79f39903498b28adacb18fe2ea046edd306295a6\tomcat-embed-core-9.0.22.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.apache.tomcat.embed\tomcat-embed-el\9.0.22\4da4b778b635a7e78ca7cd7288253e2e47b88a9f\tomcat-embed-el-9.0.22.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\javax.validation\validation-api\2.0.1.Final\cb855558e6271b1b32e716d24cb85c7f583ce09e\validation-api-2.0.1.Final.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.jboss.logging\jboss-logging\3.3.2.Final\3789d00e859632e6c6206adc0c71625559e6e3b0\jboss-logging-3.3.2.Final.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml\classmate\1.4.0\291658ac2ce2476256c7115943652c0accb5c857\classmate-1.4.0.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml.jackson.core\jackson-annotations\2.9.0\7c10d545325e3a6e72e06381afe469fd40eb701\jackson-annotations-2.9.0.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\com.fasterxml.jackson.core\jackson-core\2.9.9\bfff5af9fb8347d26bbb7959cb9b4fe9a2b0ca5e\jackson-core-2.9.9.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\ch.qos.logback\logback-core\1.2.3\864344400c3d4d92dfeb0a305dc87d953677c03c\logback-core-1.2.3.jar;C:\Users\Winfery_Wen\.gradle\caches\modules-2\files-2.1\org.apache.logging.log4j\log4j-api\2.11.2\f5e9a2ffca496057d6891a3de65128efc636e26e\log4j-api-2.11.2.jar com.graphqljava.tutorial.bookdetails.BookDetailsApplication

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.7.RELEASE)

2019-08-27 16:20:05.959  INFO 12308 --- [           main] c.g.t.b.BookDetailsApplication           : Starting BookDetailsApplication on EPCNSZUW0073 with PID 12308 (D:\springBoot\book-details\build\classes\java\main started by Winfery_Wen in D:\springBoot\book-details)
2019-08-27 16:20:05.960  INFO 12308 --- [           main] c.g.t.b.BookDetailsApplication           : No active profile set, falling back to default profiles: default
2019-08-27 16:20:06.639  INFO 12308 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2019-08-27 16:20:06.658  INFO 12308 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-08-27 16:20:06.659  INFO 12308 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.22]
2019-08-27 16:20:06.743  INFO 12308 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-08-27 16:20:06.749  INFO 12308 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 757 ms
2019-08-27 16:20:07.035  INFO 12308 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-08-27 16:20:07.178  INFO 12308 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-08-27 16:20:07.181  INFO 12308 --- [           main] c.g.t.b.BookDetailsApplication           : Started BookDetailsApplication in 1.444 seconds (JVM running for 1.923)
2019-08-27 16:21:15.060  INFO 12308 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-08-27 16:21:15.060  INFO 12308 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2019-08-27 16:21:15.066  INFO 12308 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 6 ms
2019-08-27 16:21:15.092  WARN 12308 --- [nio-8080-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.bind.MissingServletRequestParameterException: Required String parameter 'query' is not present]

Resolution

follow the log
install GraphQL Playground; open new workspace and
use url: http://localhost:8080/graphql?query=%7B__schema%20%7B%20types%20%7Bname%7D%20%7D%7D

一下的结果是在浏览器的url中输入的结果
{"data":{
    "__schema":
        {"types":
        [
            {"name":"__TypeKind"},
            {"name":"__Field"},
            {"name":"Query"},
            {"name":"__Schema"},
            {"name":"__Type"},
            {"name":"__EnumValue"},
            {"name":"__DirectiveLocation"},
            {"name":"String"},
            {"name":"Int"},
            {"name":"Book"},
            {"name":"Author"},
            {"name":"ID"},
            {"name":"__InputValue"},
            {"name":"Boolean"},
            {"name":"__Directive"}
            ]
           }
        }
}

打开GraphQL playground后就能进行使用； 但是只能使用他规定的query语句

{
  bookById(id:"book-1"){
    id
    name
    author{
      firstName
      lastName
    }
  }
}

return:

{
  "data": {
    "bookById": {
      "id": "book-1",
      "name": "Harry Potter and the Philosopher's Stone",
      "author": {
        "firstName": "Joanne",
        "lastName": "Rowling"
      }
    }
  }
}

schema:

directive @defer on FIELD
type Author {
  id: ID
  firstName: String
  lastName: String
}

type Book {
  id: ID
  name: String
  pageCount: Int
  author: Author
}

type Query {
  bookById(id: ID): Book
}

introspection

在该示例代码中， 其实是使用了GraphQL的schema来定义了只能使用的query； 其实就是使用了graphQL中的introSpection(自我检测)；我们定义了type， 但是有时候我们并不知道里面包含了哪些type， 这个时候我们就可以通过query： __schema来获取这个系统相关的信息：

{
  __schema {
    types {
      name
    }
  }
}

对应的结果就是

{
  "data": {
    "__schema": {
      "types": [
        {
          "name": "Query"
        },
        {
          "name": "Episode"
        },
        {
          "name": "Character"
        },
        {
          "name": "ID"
        },
        {
          "name": "String"
        },
        {
          "name": "Int"
        },
        {
          "name": "FriendsConnection"
        },
        {
          "name": "FriendsEdge"
        },
        {
          "name": "PageInfo"
        },
        {
          "name": "Boolean"
        },
        {
          "name": "Review"
        },
        {
          "name": "SearchResult"
        },
        {
          "name": "Human"
        },
        {
          "name": "LengthUnit"
        },
        {
          "name": "Float"
        },
        {
          "name": "Starship"
        },
        {
          "name": "Droid"
        },
        {
          "name": "Mutation"
        },
        {
          "name": "ReviewInput"
        },
        {
          "name": "__Schema"
        },
        {
          "name": "__Type"
        },
        {
          "name": "__TypeKind"
        },
        {
          "name": "__Field"
        },
        {
          "name": "__InputValue"
        },
        {
          "name": "__EnumValue"
        },
        {
          "name": "__Directive"
        },
        {
          "name": "__DirectiveLocation"
        }
      ]
    }
  }
}

而上面的例子中， 其实输入的就是该query。
现在， 我们需要知道哪些query是我们可以做的，当我们定义type系统的时候， 我们需要指定所有query的起始type， 这个时候需要使用introspection来帮我们得到：

所以query 是我们开始的类型；
查询某个type对象的信息

{
  __type(name:"Author"){
    name
    kind
    description
    
  }
}

{
  "data": {
    "__type": {
      "name": "Author",
      "kind": "OBJECT",
      "description": null
    }
  }
}

查询type内容中子域的type信息

{
  __type(name:"Author"){
    name
    kind
    fields{
      name
      type{
        name
        kind
      }
    }
    
  }
}

return

{
  "data": {
    "__type": {
      "name": "Author",
      "kind": "OBJECT",
      "fields": [
        {
          "name": "id",
          "type": {
            "name": "ID",
            "kind": "SCALAR"
          }
        },
        {
          "name": "firstName",
          "type": {
            "name": "String",
            "kind": "SCALAR"
          }
        },
        {
          "name": "lastName",
          "type": {
            "name": "String",
            "kind": "SCALAR"
          }
        }
      ]
    }
  }
}

创建一个GraphQL service就是通过定义type和field， 然后为每一个type中的每一个field提供functions， 例如:

type Query {
  me: User
}

type User {
  id: ID
  name: String
}

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

function User_name(user) {
  return user.getName();
}

一旦一个service开始运行（一般是web sevice上的url）， 这个服务器上就能发送query并执行， 收到的query首先会被检查并确保所涉及的type都是正确的， 然后运行代码中对应的函数来得到结果。
例如：

{
  me {
    name
  }
}

return

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

具体语法参照

• Queries and Mutations
  • Fields
  • Arguments
  • Aliases
  • Fragments
  • Operation Name
  • Variables
  • Directives
  • Mutations
  • Inline Fragments
• Schemas and Types
  • Type System
  • Type Language
  • Object Types and Fields
  • Arguments
  • The Query and Mutation Types
  • Scalar Types
  • Enumeration Types
  • Lists and Non-Null
  • Interfaces
  • Union Types
  • Input Types