Mutation Tutorial

The Mutation is modified from hello world example, and some of the files are updated. The first step is to make a copy of the helloworld example in light-example-4j, and then we can update several files to have a new schema and wired in the business logic.

Prepare environment

First, we need to clone light-codegen, model-config, and light-example-4j into your workspace. I am using networknt as workspace in my home directory.

cd ~/networknt
git clone https://github.com/networknt/light-codegen.git
git clone https://github.com/networknt/light-example-4j.git
git clone https://github.com/networknt/model-config.git

Let’s build light-codegen so that we can use the command line to generate the code.

cd ~/networknt/light-codegen
mvn clean install -DskipTests

Copy from helloworld

First, let’s back up the existing mutation project in light-example-4j/graphql folder.

cd ~/networknt/light-example-4j/graphql
mv mutation mutation.bak

Now let’s copy the helloworld project to mutation.

cd ~/networknt/light-example-4j/graphql
cp -r helloworld mutation

Update

Now let’s open the light-example-4j/graphql/mutation project and update some files. You can update pom.xml to change the project group and artifact but here we will just leave it as it is.

MutationSchema.java

This is the schema provider with all the business logic. Let’s use this file to replace the StarWarsSchema.java

package com.networknt.starwars.schema;

import com.networknt.graphql.router.SchemaProvider;
import graphql.schema.DataFetcher;
import graphql.schema.DataFetchingEnvironment;
import graphql.schema.GraphQLObjectType;
import graphql.schema.GraphQLSchema;

import static graphql.Scalars.GraphQLInt;
import static graphql.schema.GraphQLArgument.newArgument;
import static graphql.schema.GraphQLFieldDefinition.newFieldDefinition;

public class MutationSchema  implements SchemaProvider {
    public static class NumberHolder {
        int theNumber;

        public NumberHolder(int theNumber) {
            this.theNumber = theNumber;
        }

        public int getTheNumber() {
            return theNumber;
        }

        public void setTheNumber(int theNumber) {
            this.theNumber = theNumber;
        }


    }

    public static class Root {
        NumberHolder numberHolder;

        public Root(int number) {
            this.numberHolder = new NumberHolder(number);
        }

        public NumberHolder changeNumber(int newNumber) {
            this.numberHolder.theNumber = newNumber;
            return this.numberHolder;
        }


        public NumberHolder failToChangeTheNumber(int newNumber) {
            throw new RuntimeException("Cannot change the number");
        }
    }

    public static Root root = new Root(6);

    public static GraphQLObjectType numberHolderType = GraphQLObjectType.newObject()
            .name("NumberHolder")
            .field(newFieldDefinition()
                    .name("theNumber")
                    .type(GraphQLInt))
            .build();

    public static GraphQLObjectType queryType = GraphQLObjectType.newObject()
            .name("queryType")
            .field(newFieldDefinition()
                    .name("numberHolder")
                    .dataFetcher(new DataFetcher() {
                        @Override
                        public Object get(DataFetchingEnvironment environment) {
                            return root.numberHolder;
                        }
                    })
                    .type(numberHolderType))
            .build();

    public static GraphQLObjectType mutationType = GraphQLObjectType.newObject()
            .name("mutationType")
            .field(newFieldDefinition()
                    .name("changeTheNumber")
                    .type(numberHolderType)
                    .argument(newArgument()
                            .name("newNumber")
                            .type(GraphQLInt))
                    .dataFetcher(new DataFetcher() {
                        @Override
                        public Object get(DataFetchingEnvironment environment) {
                            Integer newNumber = environment.getArgument("newNumber");
                            return root.changeNumber(newNumber);
                        }
                    }))
            .field(newFieldDefinition()
                    .name("failToChangeTheNumber")
                    .type(numberHolderType)
                    .argument(newArgument()
                            .name("newNumber")
                            .type(GraphQLInt))
                    .dataFetcher(new DataFetcher() {
                        @Override
                        public Object get(DataFetchingEnvironment environment) {
                            Integer newNumber = environment.getArgument("newNumber");
                            return root.failToChangeTheNumber(newNumber);
                        }
                    }))
            .build();

    @Override
    public GraphQLSchema getSchema() {
        return GraphQLSchema.newSchema()
                .query(queryType)
                .mutation(mutationType)
                .build();
    }

}

service.yml

Now let’s update service.yml to replace StarWarsSchema with MutationSchema for the SchemaProvider interface.


# Singleton service factory configuration/IoC injection
singletons:
# HandlerProvider implementation
#- com.networknt.handler.HandlerProvider:
#  - com.networknt.graphql.router.GraphqlRouter
# StartupHookProvider implementations, there are one to many and they are called in the same sequence defined.
# - com.networknt.server.StartupHookProvider:
  # If you are using mask module to remove sensitive info before logging, uncomment the following line.
  # - com.networknt.server.JsonPathStartupHookProvider
  # - com.networknt.server.Test1StartupHook
  # - com.networknt.server.Test1StartupHook
# ShutdownHookProvider implementations, there are one to many and they are called in the same sequence defined.
# - com.networknt.server.ShutdownHookProvider:
  # - com.networknt.server.Test1ShutdownHook
# GraphQL schema provider interface implementation
- com.networknt.graphql.router.SchemaProvider:
  - com.networknt.starwars.schema.MutationSchema


- javax.sql.DataSource:
  - com.zaxxer.hikari.HikariDataSource:
      DriverClassName: com.mysql.jdbc.Driver
      jdbcUrl: jdbc:mysql://mysqldb:3306/oauth2?useSSL=false
      username: root
      password: my-secret-pw
      maximumPoolSize: 10
      useServerPrepStmts: true
      cachePrepStmts: true
      cacheCallableStmts: true
      prepStmtCacheSize: 10
      prepStmtCacheSqlLimit: 2048
      connectionTimeout: 2000

Build and Start server

cd ~/networknt/light-example-4j/graphql/mutation
mvn clean install exec:exec

Test

Open your browser and point to

https://localhost:8443/graphql

Now you can explore the schema on Documentation Explorer. There should be a query and a mutation.

Test query with GraphiQL

query {
  numberHolder {
    theNumber
  }
}

The result should be something like:

{
  "data": {
    "numberHolder": {
      "theNumber": 6
    }
  }
}

Test mutation with GraphiQL

mutation {
  changeTheNumber(newNumber:4) {
    theNumber
  }
}

The result should be:

{
  "data": {
    "changeTheNumber": {
      "theNumber": 4
    }
  }
}

Test the query again

With the same query in the beginning, we should have the updated value 4 returned.

query {
  numberHolder {
    theNumber
  }
}

The result should be:

{
  "data": {
    "numberHolder": {
      "theNumber": 4
    }
  }
}

Test mutation with variables

Query:

mutation ($n: Int!) {
  changeTheNumber(newNumber: $n) {
    theNumber
  }
}

Variables

{"n": 5}

And the result should be:

{
  "data": {
    "changeTheNumber": {
      "theNumber": 5
    }
  }
}

You can also use the following curl command to test.

curl -k -H 'Content-Type:application/json' -XPOST https://localhost:8443/graphql -d '{"query":"{ numberHolder { theNumber }}"}'
curl -k -H 'Content-Type:application/json' -XPOST https://localhost:8443/graphql -d '{"query":"mutation { changeTheNumber(newNumber: 4) { theNumber }}"}'
curl -k -H 'Content-Type:application/json' -XPOST https://localhost:8443/graphql -d '{"query":"{ numberHolder { theNumber }}"}'