java通过SDL方式构建graphql查询，并自定义graphql标量

实体类看这里：https://blog.csdn.net/qq_26896085/article/details/104854058

创建一个employee.graphqls文件

#这里的Date为处定义的标量，在文件的开始进行声明
scalar Date
schema {
    query: EmployeeQuery
}
type EmployeeQuery {
    employee(empNo:Int) : Employee
}
type Employee {
    empNo: Int
    birthDate: Date
    firstName: String
    lastName: String
    hireDate: Date
    gender: String
}

DateScalarType.java

写法参考源码Scalars中的写法

package com.woodie.modifyoriginal;

import graphql.schema.*;

import java.text.SimpleDateFormat;
import java.util.Date;

// 需要继承GraphQLScalarType
public class DateScalarType extends GraphQLScalarType {

    public DateScalarType() {
        super("Date", "Date value", new Coercing() {

            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

            public String serialize(Object input) {
                return sdf.format(input);
            }

            public String parseValue(Object input) {
                return this.serialize(sdf.format(input));
            }

            public String parseLiteral(Object input) {
                if (!(input instanceof Date)) {
                    throw new CoercingParseLiteralException("Expected AST type 'Date' but was ");
                } else {
                    return sdf.format(input);
                }
            }
        });
    }
}

GraphqlSDLDemo.java

package com.woodie;

import com.woodie.entity.Employee;
import com.woodie.modifyoriginal.DateScalarType;
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;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class GraphqlSDLDemo {

    public static void main(String[] args)  {

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        try {
            String fileName = "employee.graphqls";
            String fileContent = IOUtils.toString(GraphqlSDLDemo.class.getClassLoader().getResource(fileName), "utf-8");
            TypeDefinitionRegistry typeRegistry = new SchemaParser().parse(fileContent);

            // 解决的是数据的查询
            RuntimeWiring wiring = RuntimeWiring.newRuntimeWiring()
                    .type("EmployeeQuery", builder ->
                                    builder.dataFetcher("employee", environment ->{
                                        Integer id = environment.getArgument("empNo");
                                        return  Employee.builder().birthDate(new Date()).empNo(10001).gender("M").firstName("Woodie").lastName("Wang").hireDate(sdf.parse("2222- 03-14")).build();
                                    })
                    )
                    // 有处定义的标量时需要传入自定义的ScallarType()类，
                    .scalar(new DateScalarType())
                    .build();
            GraphQLSchema graphQLSchema= new SchemaGenerator().makeExecutableSchema(typeRegistry,wiring);

            GraphQL graphQL = GraphQL.newGraphQL(graphQLSchema).build();
            String query = "{employee(empNo:10001){empNo， birthDate， hireDate， lastName}}";
            ExecutionResult result = graphQL.execute(query);
            System.out.println(result.toSpecification());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}