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.
- DSL builder style. Make it easier to read and use.
- Support Cursor Connection and Input Object Mutation in Relay.
Adding Kraph to build.gradle
repositories {
jcenter()
}
dependencies {
compile "me.lazmaid.kraph:kraph:x.y.z"
}
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.
-
query
andmutation
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
andfieldObject
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 aMap<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") } } }
func
represents a Field inside a Mutation block that follows the Relay Input Object Mutations specification.mutation { userLogin(input: {email: "[email protected]", password: "abcd1234"}) { accessToken user { id email } } }
Kraph { mutation { func("userLogin", input = mapOf("email" to "[email protected]", "password" to "abcd1234")) { field("accessToken") fieldObject("user") { field("id") field("email") } } } }
cursorConnection
represents a Field that follows the Relay Cursor Connections specificationquery { users(first: 10, after: "user::1234") { edges { node { id name } } } }
Kraph { cursorConnection("users", first = 10, after = "user::1234") { edges { node { field("id") field("name") } } } }
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()
andrequestOperationName()
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 thequery
,variables
, andoperationName
parameters, respectively, and so are good for creating GET requests. Please note thatrequestVariableString()
will always returnnull
until variable support is implemented.
We use Github issues for tracking bugs and requests. Any feedback and/or PRs is welcome.