java 使用GraphQL-关联对象

GraphQL并不会实现关联查询，数据关联需要程序自己实现

官网首页有介绍获取多个资源只需要一个请求，如想获取用户信息和身份证信息，原来需要先查用户信息，再通过用户id查询身份证信息，而在GraphQL中一次请求就可以实现。

对于这个观点我不敢苟同，可能我还没有体会到这种感觉，我认为只要需求明确，多个资源一次请求在RESTFUl中同样可以实现。

废话不说了，进入在正题

　　之前已经实现了对user对象的查询操作，现在对user添加一个card属性，操作user对象时可以关联到card信息

User.java

public class User {
    private int age;
    private long id;
    private String name;
    private Card card;

    public User(int age, long id, String name, Card card) {
        this.age = age;
        this.id = id;
        this.name = name;
        this.card = card;
    }

    public Card getCard() {
        return card;
    }

    public void setCard(Card card) {
        this.card = card;
    }

    public User(int age, long id, String name) {
        this.age = age;
        this.id = id;
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

Card.java

public class Card {
    private String cardNumber;
    private Long userId;

    public Card(String cardNumber, Long userId) {
        this.cardNumber = cardNumber;
        this.userId = userId;
    }

    public String getCardNumber() {
        return cardNumber;
    }

    public void setCardNumber(String cardNumber) {
        this.cardNumber = cardNumber;
    }

    public Long getUserId() {
        return userId;
    }

    public void setUserId(Long userId) {
        this.userId = userId;
    }
}

user.graphqls

#对应的User定义如下
schema {    #定义查询
    query: UserQuery
}
type UserQuery {    #定义查询类型
    user(id:Long) : User    #指定对象以及参数类型
}
type User { #定义对象
    id: Long!   #!表示非空
    name:String
    age:Int
    card:Card
}

type Card {
    cardNumber:String
    userId:Long
}

demo

import clc.bean.Card;
import clc.bean.User;
import graphql.ExecutionResult;
import graphql.GraphQL;
import graphql.schema.GraphQLSchema;
import graphql.schema.idl.RuntimeWiring;
import graphql.schema.idl.SchemaGenerator;
import graphql.schema.idl.SchemaParser;
import graphql.schema.idl.TypeDefinitionRegistry;
import org.apache.commons.io.IOUtils;


/**
 * ClassName: GraphQLSDLDemo<br/>
 * Description: <br/>
 * date: 2019/6/28 11:19 AM<br/>
 *
 * @author chengluchao
 * @since JDK 1.8
 */

public class GraphQLSDLDemo2 {
    public static void main(String[] args) throws Exception {
        //读取graphqls文件
        String fileName = "user.graphqls";
        String fileContent = IOUtils.toString(GraphQLSDLDemo2.class.getClassLoader().getResource(fileName), "UTF-8");
        //解析文件
        TypeDefinitionRegistry typeDefinitionRegistry = new SchemaParser().parse(fileContent);

        RuntimeWiring wiring = RuntimeWiring.newRuntimeWiring()
                .type("UserQuery", builder ->
                        builder.dataFetcher("user", environment -> {
                            Long id = environment.getArgument("id");
                            Card card = new Card("123456", id);
                            return new User(18, id, "user0" + id, card);
                        })
                )
                .build();

        GraphQLSchema graphQLSchema = new SchemaGenerator().makeExecutableSchema(typeDefinitionRegistry, wiring);

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

        String query = "{user(id:15){id,name,age,card{cardNumber,userId}}}";
        ExecutionResult result = graphQL.execute(query);

        System.out.println("query: " + query);
        System.out.println(result.toSpecification());
    }
}

query: {user(id:15){id,name,age,card{cardNumber,userId}}}
{data={user={id=15, name=user015, age=18, card={cardNumber=123456, userId=15}}}}

再次强调，关联信息是程序控制的，并不是GraphQL