https://github.com/killbill/technical-support/issues/188

Details for Hello World plugin HelloWorldInvoicePluginApi class.

Author: KBbitsP

userguide/tutorials/plugin_development.adoc

@@ -172,6 +172,16 @@ The https://github.com/killbill/killbill-hello-world-java-plugin/blob/3aa938d19f
 
 The https://github.com/killbill/killbill-hello-world-java-plugin/blob/3aa938d19fdfba81c7c035b45c3f17cac74db177/src/main/java/org/killbill/billing/plugin/helloworld/HelloWorldPaymentPluginApi.java[_HelloWorldPaymentPluginApi_] class provides sample code for developing a payment plugin. It implements the https://github.com/killbill/killbill-plugin-api/blob/d9eca5af0e37541069b1c608f95e100dbe13b301/payment/src/main/java/org/killbill/billing/payment/plugin/api/PaymentPluginApi.java[_PaymentPluginApi_] interface. You can extend this class as required to develop a payment plugin. See the https://docs.killbill.io/latest/payment_plugin.html[_Payment Plugin Tutorial_] for further information.
 
+=== HelloWorldInvoicePluginApi
+
+The https://github.com/killbill/killbill-hello-world-java-plugin/blob/3aa938d19fdfba81c7c035b45c3f17cac74db177/src/main/java/org/killbill/billing/plugin/helloworld/HelloWorldInvoicePluginApi.java[_HelloWorldInvoicePluginApi_] class provides sample code for developing an invoice plugin. It implements the https://github.com/killbill/killbill-plugin-api/blob/a20776687fc61ce4ca94d84e2b117e4cce0a255c/invoice/src/main/java/org/killbill/billing/invoice/plugin/api/InvoicePluginApi.java[_InvoicePluginApi_] interface. You can extend this class as required to develop an invoice plugin. See the https://docs.killbill.io/latest/invoice_plugin.html[_https://docs.killbill.io/latest/invoice_plugin_] for further information. The HelloWorldInvoicePluginApi class shows examples of adding three item types. 
+
+* https://github.com/killbill/killbill-hello-world-java-plugin/blob/master/src/main/java/org/killbill/billing/plugin/helloworld/HelloWorldInvoicePluginApi.java#L83[_External_Charge_]: It applies a fixed static charge linked to the very first item of the current invoice being generated. An example could be, a fixed charge that you always wish to add to the invoice, like handling charge, acquisition cost etc. 
+
+* https://github.com/killbill/killbill-hello-world-java-plugin/blob/master/src/main/java/org/killbill/billing/plugin/helloworld/HelloWorldInvoicePluginApi.java#L78[_Tax_Item_]: It applies a fixed charge linked to the very first item of the current invoice being generated. For simplicity this is fixed in this example, however, it could be percentage based calculation as well.
+
+* https://github.com/killbill/killbill-hello-world-java-plugin/blob/master/src/main/java/org/killbill/billing/plugin/helloworld/HelloWorldInvoicePluginApi.java#L88[_Item_Adj_]: It checks the historical invoices for the account and applies the adjustment linked to each item of the first invoice where adjustment item type is not present.
+
 === Other Classes
 
 In addition to the classes listed above, some of the other classes in the `hello-world-plugin` are as follows: