Kraph

In short, this is a GraphQL request JSON body builder for Kotlin. It will
generate the JSON string for request body that work with GraphQL Server.
For example, we have this GraphQL query to list all notes:

query {
    notes {
        id
        createdDate
        content
        author {
            name
            avatarUrl(size: 100)
        }
    }
}

Which is written in Kotlin using Kraph like this:

Kraph {
    query {
        fieldObject("notes") {
            field("id")
            field("createdDate")
            field("content")
            fieldObject("author") {
                field("name")
                field("avatarUrl", mapOf("size" to 100))
            }
        }
    }
}

As you can see, we can achieve our goal with just a few tweaks from the original query.

NOTE: Kraph is still in an early stage. The usage may change in further development.

Features

• DSL builder style. Make it easier to read and use.
• Support Cursor Connection and Input Object Mutation in Relay.

Set up

Adding Kraph to build.gradle

repositories {
    jcenter()
}

dependencies {
    compile "me.lazmaid.kraph:kraph:x.y.z"
}

Guide

If you are not familiar with GraphQL syntax, it is recommended to read the
GraphQL introduction for an overview of how Graphql
works. Usually, you should be able to use queries from other tools (e.g.
GraphiQL) with a few tweaks.
First, let's see what Kraph provides for you.

Simple GraphQL

• query and mutation represents the Query and Mutation operations of GraphQL.
  The name of the query or mutaton can be passed as a string.

  GraphQL:

  query GetUsers {
    ...
  }
  

  Kraph:

  Kraph {
      query("GetUsers") {
          ...
      }
  }
  

  GraphQL:

  mutation UpdateUserProfile {
    ...
  }
  

  Kraph:

  Kraph {
      mutation("UpdateUserProfile") {
          ...
      }
  }
  

• field and fieldObject represent accessors for fields. Though there are
  technically no differences, fieldObject may be chosen for clarity to indicate
  that a field must contain another set of nested fields as an argument.
  Both of them take a Map<String, Any> that maps Kotlin data types to the
  GraphQL data types for input objects.

  query {
    users {
      name
      email
      avatarUrl(size: 100)
    }
  }
  

  Kraph {
      query {
          fieldObject("users") {
              field("name")
              field("email")
              field("avatarUrl", args = mapOf("size" to 100))
          }
      }
  }
  

• fragment provides a mechanism for creating GraphQL Fragments. To use a fragment
  in a query requires two steps. The first is to define the fragment, letting
  Kraph know how to handle it later:

  fragment UserFragment on User {
    name
    email
    avatarUrl(size: 100)
  }
  

  Kraph.defineFragment("UserFragment") {
      field("name")
      field("email")
      field("avatarUrl", mapOf("size" to 100))
  }
  

  Then, when you are creating your query, you can simply use the fragment and
  its fields will be expanded:

  query {
    users {
      ...UserFragment
    }
  }
  

  Kraph {
      query("GetUsers") {
          fieldObject("users") {
              fragment("UserFragment")
          }
      }
  }
  

Relay

• func represents a Field inside a Mutation block that follows the
  Relay Input Object Mutations specification.

  mutation {
    userLogin(input: {email: "hello@taskworld.com", password: "abcd1234"}) {
      accessToken
      user {
        id
        email
      }
    }
  }
  

  Kraph {
      mutation {
          func("userLogin", input = mapOf("email" to "hello@taskworld.com", "password" to "abcd1234")) {
              field("accessToken")
              fieldObject("user") {
                  field("id")
                  field("email")
              }
          }
      }
  }
  

• cursorConnection represents a Field that follows the
  Relay Cursor Connections specification

  query {
     users(first: 10, after: "user::1234") {
      edges {
        node {
          id
          name
        }
      }
    }
  }
  

  Kraph {
      cursorConnection("users", first = 10, after = "user::1234") {   
          edges {
              node {
                  field("id")
                  field("name")
              }
          }
      }
  }
  

Request/Query String

• toRequestString() will generate a JSON body to send in POST request.
• toGraphQueryString() will give you the formatted GraphQL string. This is
  very useful for debugging.

  val query = Kraph {
      query {
          fieldObject("users") {
              field("name")
              field("email")
              field("avatarUrl", args = mapOf("size" to 100))
          }
      }
  }    
  
  println(query.toRequestString())
  /*
   * Result:
   * {"query": "query {\nnotes {\nid\ncreatedDate\ncontent\nauthor {\nname\navatarUrl(size: 100)\n}\n}\n}", "variables": null, "operationName": null}
   */
  println(query.toGraphQueryString())
  /*
   * Result:
   * query {
   *   notes {
   *     id
   *     createdDate
   *     content
   *     author {
   *       name
   *       avatarUrl(size: 100)
   *     }
   *   }
   * }
   */
  

• requestQueryString(), requestVariableString() and requestOperationName()
  provide more fine grained access to the components of the full request string,
  which are sometimes necessary depending on your HTTP request builder and
  GraphQL server setup. They provide the values for the query, variables,
  and operationName parameters, respectively, and so are good for creating
  GET requests. Please note that requestVariableString() will always return
  null until variable support is implemented.

Contributing to Kraph

We use Github issues for tracking bugs and requests.
Any feedback and/or PRs is welcome.