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Custom scalar types

If the remote service contains custom scalar types represented as strings in GraphQL documents, a typesafe client can learn to understand these types through introducing a class that represents them. The class has to contain logic necessary for serializing and deserializing from/to raw strings.

A model class is considered to represent a scalar GraphQL type if it contains a static builder method named of, valueOf, or parse whose sole parameter is a java.lang.String and it returns an instance of the class itself. The name of the GraphQL type is assumed to be equal to the short name of the class.

For example, if the server supports a URL type (there is a scalar URL clause in the schema), create a class that represents a value for URL:

public class URL {

    private String value;

    public URL(String value) {
        this.value = value;

    public static URL valueOf(String value) {  // <1>
        return new URL(value);

    public String toString() {   // <2>
        return value;
  • <1> The static valueOf(String) method will be used for deserializing a URL from a string.
  • <2> The toString() will be used for serializing a URL into a string to be sent to the GraphQL service