Introducing InitiatedBy annotation to be used on initiated flows to simplify flow registration.

This removes the need to do manual registration using the PluginServiceHub. As a result CordaPluginRegistry.servicePlugins is no longer needed. For oracles and services there is a CorDappService annotation.

I've also fixed the InitiatingFlow annotation such that client flows can be customised (sub-typed) without it breaking the flow sessions.

samples/trader-demo/src/integration-test/kotlin/net/corda/traderdemo/TraderDemoTest.kt

@@ -16,6 +16,7 @@ import net.corda.node.services.transactions.SimpleNotaryService
 import net.corda.nodeapi.User
 import net.corda.testing.BOC
 import net.corda.testing.node.NodeBasedTest
+import net.corda.traderdemo.flow.BuyerFlow
 import net.corda.traderdemo.flow.SellerFlow
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.Test
@@ -36,6 +37,8 @@ class TraderDemoTest : NodeBasedTest() {
                 startNode(DUMMY_NOTARY.name, advertisedServices = setOf(ServiceInfo(SimpleNotaryService.type)))
         ).getOrThrow()
 
+        nodeA.registerInitiatedFlow(BuyerFlow::class.java)
+
         val (nodeARpc, nodeBRpc) = listOf(nodeA, nodeB).map {
             val client = CordaRPCClient(it.configuration.rpcAddress!!)
             client.start(demoUser[0].username, demoUser[0].password).proxy
@@ -57,12 +60,8 @@ class TraderDemoTest : NodeBasedTest() {
         val executor = Executors.newScheduledThreadPool(1)
         poll(executor, "A to be notified of the commercial paper", pollInterval = 100.millis) {
             val actualPaper = listOf(clientA.commercialPaperCount, clientB.commercialPaperCount)
-            if (actualPaper == expectedPaper) {
-                Unit
-            } else {
-                null
-            }
-        }.get()
+            if (actualPaper == expectedPaper) Unit else null
+        }.getOrThrow()
         executor.shutdown()
         assertThat(clientA.dollarCashBalance).isEqualTo(95.DOLLARS)
         assertThat(clientB.dollarCashBalance).isEqualTo(5.DOLLARS)

samples/trader-demo/src/main/kotlin/net/corda/traderdemo/flow/BuyerFlow.kt

@@ -4,36 +4,24 @@ import co.paralleluniverse.fibers.Suspendable
 import net.corda.contracts.CommercialPaper
 import net.corda.core.contracts.Amount
 import net.corda.core.contracts.TransactionGraphSearch
-import net.corda.core.identity.Party
+import net.corda.core.div
 import net.corda.core.flows.FlowLogic
+import net.corda.core.flows.InitiatedBy
+import net.corda.core.identity.Party
 import net.corda.core.node.NodeInfo
-import net.corda.core.node.PluginServiceHub
-import net.corda.core.serialization.SingletonSerializeAsToken
 import net.corda.core.transactions.SignedTransaction
 import net.corda.core.utilities.Emoji
 import net.corda.core.utilities.ProgressTracker
 import net.corda.core.utilities.unwrap
 import net.corda.flows.TwoPartyTradeFlow
-import java.nio.file.Paths
 import java.util.*
 
-class BuyerFlow(val otherParty: Party,
-                private val attachmentsDirectory: String,
-                override val progressTracker: ProgressTracker = ProgressTracker(STARTING_BUY)) : FlowLogic<Unit>() {
+@InitiatedBy(SellerFlow::class)
+class BuyerFlow(val otherParty: Party) : FlowLogic<Unit>() {
 
     object STARTING_BUY : ProgressTracker.Step("Seller connected, purchasing commercial paper asset")
 
-    class Service(services: PluginServiceHub) : SingletonSerializeAsToken() {
-        init {
-            // Buyer will fetch the attachment from the seller automatically when it resolves the transaction.
-            // For demo purposes just extract attachment jars when saved to disk, so the user can explore them.
-            val attachmentsPath = (services.storageService.attachments).let {
-                it.automaticallyExtractAttachments = true
-                it.storePath
-            }
-            services.registerServiceFlow(SellerFlow::class.java) { BuyerFlow(it, attachmentsPath.toString()) }
-        }
-    }
+    override val progressTracker: ProgressTracker = ProgressTracker(STARTING_BUY)
 
     @Suspendable
     override fun call() {
@@ -72,8 +60,15 @@ class BuyerFlow(val otherParty: Party,
                 followInputsOfType = CommercialPaper.State::class.java)
         val cpIssuance = search.call().single()
 
+        // Buyer will fetch the attachment from the seller automatically when it resolves the transaction.
+        // For demo purposes just extract attachment jars when saved to disk, so the user can explore them.
+        val attachmentsPath = (serviceHub.storageService.attachments).let {
+            it.automaticallyExtractAttachments = true
+            it.storePath
+        }
+
         cpIssuance.attachments.first().let {
-            val p = Paths.get(attachmentsDirectory, "$it.jar")
+            val p = attachmentsPath / "$it.jar"
             println("""
 
 The issuance of the commercial paper came with an attachment. You can find it expanded in this directory:

samples/trader-demo/src/main/kotlin/net/corda/traderdemo/plugin/TraderDemoPlugin.kt

@@ -1,10 +0,0 @@
-package net.corda.traderdemo.plugin
-
-import net.corda.core.identity.Party
-import net.corda.core.node.CordaPluginRegistry
-import net.corda.traderdemo.flow.BuyerFlow
-import java.util.function.Function
-
-class TraderDemoPlugin : CordaPluginRegistry() {
-    override val servicePlugins = listOf(Function(BuyerFlow::Service))
-}

samples/trader-demo/src/main/resources/META-INF/services/net.corda.core.node.CordaPluginRegistry

@@ -1,2 +0,0 @@
-# Register a ServiceLoader service extending from net.corda.core.node.CordaPluginRegistry
-net.corda.traderdemo.plugin.TraderDemoPlugin