Added a json serializer for PublicKeyTree

Typo fixes, other minor refactorings

core/src/main/kotlin/com/r3corda/core/crypto/PublicKeyTree.kt

@@ -9,9 +9,9 @@ import java.security.PublicKey
 /**
  * A tree data structure that enables the representation of composite public keys.
  *
- * It the simplest case it may just contain a single node encapsulating a [PublicKey] – a [Leaf].
+ * In the simplest case it may just contain a single node encapsulating a [PublicKey] – a [Leaf].
  *
- * For more complex scenarios, such as *"Both Alice and Bob need to sign to consume a sate S"*, we can represent
+ * For more complex scenarios, such as *"Both Alice and Bob need to sign to consume a state S"*, we can represent
  * the requirement by creating a tree with a root [Node], and Alice and Bob as children – [Leaf]s.
  * The root node would specify *weights* for each of its children and a *threshold* – the minimum total weight required
  * (e.g. the minimum number of child signatures required) to satisfy the tree signature requirement.

core/src/test/kotlin/com/r3corda/core/crypto/PublicKeyTreeTests.kt

@@ -2,6 +2,7 @@ package com.r3corda.core.crypto
 
 import com.r3corda.core.serialization.OpaqueBytes
 import org.junit.Test
+import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 
 class PublicKeyTreeTests {
@@ -46,4 +47,15 @@ class PublicKeyTreeTests {
 
         assertTrue { aliceAndBobOrCharlie.isFulfilledBy(signatures.byKeys()) }
     }
+
+    @Test
+    fun `encoded tree decodes correctly`() {
+        val aliceAndBob = PublicKeyTree.Builder().addKeys(alicePublicKey, bobPublicKey).build()
+        val aliceAndBobOrCharlie = PublicKeyTree.Builder().addKeys(aliceAndBob, charliePublicKey).build(threshold = 1)
+
+        val encoded = aliceAndBobOrCharlie.toBase58String()
+        val decoded = PublicKeyTree.parseFromBase58(encoded)
+
+        assertEquals(decoded, aliceAndBobOrCharlie)
+    }
 }

node/src/main/kotlin/com/r3corda/node/utilities/JsonSupport.kt

@@ -50,6 +50,10 @@ object JsonSupport {
         cordaModule.addSerializer(EdDSAPublicKey::class.java, PublicKeySerializer)
         cordaModule.addDeserializer(EdDSAPublicKey::class.java, PublicKeyDeserializer)
 
+        // For public key trees
+        cordaModule.addSerializer(PublicKeyTree::class.java, PublicKeyTreeSerializer)
+        cordaModule.addDeserializer(PublicKeyTree::class.java, PublicKeyTreeDeserializer)
+
         mapper.registerModule(timeModule)
         mapper.registerModule(cordaModule)
         mapper.registerModule(KotlinModule())
@@ -148,4 +152,20 @@ object JsonSupport {
             }
         }
     }
+
+    object PublicKeyTreeSerializer : JsonSerializer<PublicKeyTree>() {
+        override fun serialize(obj: PublicKeyTree, generator: JsonGenerator, provider: SerializerProvider) {
+            generator.writeString(obj.toBase58String())
+        }
+    }
+
+    object PublicKeyTreeDeserializer : JsonDeserializer<PublicKeyTree>() {
+        override fun deserialize(parser: JsonParser, context: DeserializationContext): PublicKeyTree {
+            return try {
+                PublicKeyTree.parseFromBase58(parser.text)
+            } catch (e: Exception) {
+                throw JsonParseException(parser, "Invalid public key tree ${parser.text}: ${e.message}")
+            }
+        }
+    }
 }