This is a sample implementation of a Demand Driven API which returns different attributes of Customer as requested in the incoming request. This application explains how graph-ql can be used in a complex multi entity schema; for e.g. in this application we assume that a customer can have multiple accounts, each account could have different attributes / charecterstics etc.
This application can be tested using PostMan or its equivalent. It's a Spring Boot application which uses GraphQL Starter project and runs on default port, 8080. Sample request, { customer { firstName accounts { accountNumber cashBalance { availableCash totalCash } mutualFundHoldings { fundIdentifier fundName, unitsHeld } } address { postCode } } }
In this application, I have modelled two types of accounts, DematAccount and SavingsAccount, both of which implement Account interface. Ideally, I wanted my DematAccount to implement multiple interfaces, for e.g. DematAccount implements Accounts, SupportsCashBalance, SupportsMutualFunds, SupportsBrokerageAssets etc. etc. This way I wanted to keep the behaviour of an Account flexible so that both of the Accounts (DemantAccount and SavingsAccount) can be modelled independently.
While I could do the object modelling, I could not figure out the right way to create the schema file for this. This is something whihc needs to be worked upon in coming days/weeks.