Added default value support

FasterXML · Dec 5, 2019 · ed96d11 · ed96d11
1 parent 118acfa
commit ed96d11
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Showing 5 changed files with 89 additions and 5 deletions.
diff --git a/src/main/scala/com/fasterxml/jackson/module/scala/introspect/BeanDescriptor.scala b/src/main/scala/com/fasterxml/jackson/module/scala/introspect/BeanDescriptor.scala
@@ -2,4 +2,10 @@ package com.fasterxml.jackson.module.scala.introspect
 
 import scala.language.existentials
 
-case class BeanDescriptor(beanType: Class[_], properties: Seq[PropertyDescriptor])
+case class BeanDescriptor(beanType: Class[_], properties: Seq[PropertyDescriptor]) {
+  val constructorParameters: Map[Int, ConstructorParameter] = {
+    properties.collect {
+      case PropertyDescriptor(_, Some(param), _, _, _, _, _) => param.index -> param
+    }.toMap
+  }
+}
diff --git a/src/main/scala/com/fasterxml/jackson/module/scala/introspect/BeanIntrospector.scala b/src/main/scala/com/fasterxml/jackson/module/scala/introspect/BeanIntrospector.scala
@@ -58,13 +58,30 @@ object BeanIntrospector {
       val primaryConstructor = c.getConstructors.headOption
       val debugCtorParamNames = primaryConstructor.toIndexedSeq.flatMap(getCtorParams)
       val index = debugCtorParamNames.indexOf(name)
+      val companion = findCompanionObject(c)
       if (index >= 0) {
-        Some(ConstructorParameter(primaryConstructor.get, index, None))
+        Some(ConstructorParameter(primaryConstructor.get, index, findConstructorDefaultValue(companion, index)))
       } else {
         findConstructorParam(c.getSuperclass, name)
       }
     }
 
+    def findConstructorDefaultValue(maybeCompanion: Option[AnyRef], index: Int): Option[() => AnyRef] = {
+      val methodName = "$lessinit$greater$default$" + (index + 1)
+      maybeCompanion.flatMap(companion => companion.getClass.getMethods.toStream.collectFirst {
+        case method if method.getName == methodName && method.getParameterCount == 0 =>
+          () => method.invoke(companion)
+      })
+    }
+
+    def findCompanionObject(c: Class[_]): Option[AnyRef] = {
+      try {
+        Some(c.getClassLoader.loadClass(c.getName + "$").getDeclaredField("MODULE$").get(null))
+      } catch {
+        case e: Exception => None
+      }
+    }
+
     val hierarchy: Seq[Class[_]] = {
       @tailrec
       def next(c: Class[_], acc: List[Class[_]]): List[Class[_]] = {

diff --git a/src/main/scala/com/fasterxml/jackson/module/scala/introspect/PropertyDescriptor.scala b/src/main/scala/com/fasterxml/jackson/module/scala/introspect/PropertyDescriptor.scala
@@ -7,7 +7,7 @@ import com.fasterxml.jackson.module.scala.util.Implicits._
 
 import scala.language.existentials
 
-case class ConstructorParameter(constructor: Constructor[_], index: Int, defaultValueMethod: Option[Method])
+case class ConstructorParameter(constructor: Constructor[_], index: Int, defaultValue: Option[() => AnyRef])
 
 case class PropertyDescriptor(name: String,
                               param: Option[ConstructorParameter],

diff --git a/...ala/com/fasterxml/jackson/module/scala/introspect/ScalaAnnotationIntrospectorModule.scala b/...ala/com/fasterxml/jackson/module/scala/introspect/ScalaAnnotationIntrospectorModule.scala
@@ -3,14 +3,17 @@ package com.fasterxml.jackson.module.scala.introspect
 import java.lang.annotation.Annotation
 
 import com.fasterxml.jackson.annotation.JsonCreator
+import com.fasterxml.jackson.databind.{BeanDescription, DeserializationConfig, DeserializationContext}
 import com.fasterxml.jackson.databind.`type`.ClassKey
+import com.fasterxml.jackson.databind.deser.{CreatorProperty, NullValueProvider, SettableBeanProperty, ValueInstantiator, ValueInstantiators}
+import com.fasterxml.jackson.databind.deser.std.StdValueInstantiator
 import com.fasterxml.jackson.databind.introspect._
-import com.fasterxml.jackson.databind.util.LRUMap
+import com.fasterxml.jackson.databind.util.{AccessPattern, LRUMap}
 import com.fasterxml.jackson.module.paranamer.ParanamerAnnotationIntrospector
 import com.fasterxml.jackson.module.scala.JacksonModule
 import com.fasterxml.jackson.module.scala.util.Implicits._
 
-object ScalaAnnotationIntrospector extends NopAnnotationIntrospector
+object ScalaAnnotationIntrospector extends NopAnnotationIntrospector with ValueInstantiators
 {
   private [this] val _descriptorCache = new LRUMap[ClassKey, BeanDescriptor](16, 100)
 
@@ -114,9 +117,54 @@ object ScalaAnnotationIntrospector extends NopAnnotationIntrospector
       JsonCreator.Mode.PROPERTIES
     } else null
   }
+
+  class ScalaValueInstantiator(delegate: StdValueInstantiator, config: DeserializationConfig, descriptor: BeanDescriptor) extends StdValueInstantiator(delegate) {
+
+    private val overriddenConstructorArguments = {
+      val args = delegate.getFromObjectArguments(config)
+
+      args.map {
+        case creator: CreatorProperty =>
+          // Locate the constructor param that matches it
+          descriptor.properties.find(_.param.exists(_.index == creator.getCreatorIndex)) match {
+            case Some(PropertyDescriptor(name, Some(ConstructorParameter(_, _, Some(defaultValue))), _, _, _, _, _)) =>
+              creator.withNullProvider(new NullValueProvider {
+                override def getNullValue(ctxt: DeserializationContext): AnyRef = defaultValue()
+
+                override def getNullAccessPattern: AccessPattern = AccessPattern.DYNAMIC
+              })
+            case _ => creator
+          }
+        case other => other
+      }
+    }
+
+    override def getFromObjectArguments(config: DeserializationConfig): Array[SettableBeanProperty] = {
+      overriddenConstructorArguments
+    }
+  }
+
+  override def findValueInstantiator(config: DeserializationConfig, beanDesc: BeanDescription,
+    defaultInstantiator: ValueInstantiator): ValueInstantiator = {
+
+    if (isMaybeScalaBeanType(beanDesc.getBeanClass)) {
+
+      val descriptor = _descriptorFor(beanDesc.getBeanClass)
+      if (descriptor.properties.exists(_.param.exists(_.defaultValue.isDefined))) {
+        defaultInstantiator match {
+          case std: StdValueInstantiator =>
+            new ScalaValueInstantiator(std, config, descriptor)
+          case other =>
+            throw new IllegalArgumentException("Cannot customise a non StdValueInstantiatiator: " + other.getClass)
+        }
+      } else defaultInstantiator
+
+    } else defaultInstantiator
+  }
 }
 
 trait ScalaAnnotationIntrospectorModule extends JacksonModule {
   this += { _.appendAnnotationIntrospector(new ParanamerAnnotationIntrospector()) }
   this += { _.appendAnnotationIntrospector(ScalaAnnotationIntrospector) }
+  this += { _.addValueInstantiators(ScalaAnnotationIntrospector) }
 }
diff --git a/src/test/scala/com/fasterxml/jackson/module/scala/deser/CreatorTest.scala b/src/test/scala/com/fasterxml/jackson/module/scala/deser/CreatorTest.scala
@@ -38,8 +38,11 @@ object CreatorTest
       this(script, 0)
     }
   }
+
+  case class ConstructorWithDefaultValues(s: String = "some string", i: Int = 10, dummy: String)
 }
 
+
 @RunWith(classOf[JUnitRunner])
 class CreatorTest extends DeserializationFixture {
   import CreatorTest._
@@ -104,4 +107,14 @@ class CreatorTest extends DeserializationFixture {
     val roundTrip = f.readValue[MultipleConstructorsAnn](bean)
     roundTrip shouldEqual orig
   }
+
+  it should "support default values" in { f =>
+    val deser = f.readValue[ConstructorWithDefaultValues]("""{}""")
+    deser.s shouldEqual "some string"
+    deser.i shouldEqual 10
+    deser.dummy shouldEqual null
+    val deser2 = f.readValue[ConstructorWithDefaultValues]("""{"s":"passed","i":5}""")
+    deser2.s shouldEqual "passed"
+    deser2.i shouldEqual 5
+  }
 }