Significant improvement in deserialization speed

pom.xml

@@ -114,7 +114,6 @@
     </dependencies>
 
     <build>
-        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
         <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
         <plugins>
             <plugin>
@@ -129,6 +128,13 @@
                         <goals>
                             <goal>compile</goal>
                         </goals>
+                        <configuration>
+                            <sourceDirs>
+                                <source>${project.basedir}/target/generated-sources</source>
+                                <source>${project.basedir}/src/main/java</source>
+                                <source>${project.basedir}/src/main/kotlin</source>
+                            </sourceDirs>
+                        </configuration>
                     </execution>
 
                     <execution>
@@ -145,10 +151,12 @@
                     </execution>
                 </executions>
             </plugin>
+
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
             </plugin>
+
             <plugin>
                 <!-- Inherited from oss-base. Generate PackageVersion.java.-->
                 <groupId>com.google.code.maven-replacer-plugin</groupId>
@@ -160,6 +168,7 @@
                     </execution>
                 </executions>
             </plugin>
+
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
@@ -168,6 +177,32 @@
                     <showDeprecation>true</showDeprecation>
                     <showWarnings>true</showWarnings>
                 </configuration>
+                <executions>
+                    <!-- Replacing default-compile as it is treated specially by maven -->
+                    <execution>
+                        <id>default-compile</id>
+                        <phase>none</phase>
+                    </execution>
+                    <!-- Replacing default-testCompile as it is treated specially by maven -->
+                    <execution>
+                        <id>default-testCompile</id>
+                        <phase>none</phase>
+                    </execution>
+                    <execution>
+                        <id>java-compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>java-test-compile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>testCompile</goal>
+                        </goals>
+                    </execution>
+                </executions>
             </plugin>
 
             <!-- 02-Nov-2020, tatu: Add JDK9+ module info with Moditect -->

src/main/java/com/fasterxml/jackson/module/kotlin/SpreadWrapper.java

@@ -0,0 +1,47 @@
+package com.fasterxml.jackson.module.kotlin;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
+/**
+ * Wrapper to avoid costly calls using spread operator.
+ * @since 2.13
+ */
+class SpreadWrapper {
+    public static <T> Constructor<T> getConstructor(
+            @NotNull Class<T> clazz,
+            @NotNull Class<?>[] parameterTypes
+    ) throws NoSuchMethodException {
+        return clazz.getConstructor(parameterTypes);
+    }
+
+    public static <T> T newInstance(
+            @NotNull Constructor<T> constructor,
+            @NotNull Object[] initargs
+    ) throws InvocationTargetException, InstantiationException, IllegalAccessException {
+        return constructor.newInstance(initargs);
+    }
+
+    public static Method getDeclaredMethod(
+            @NotNull Class<?> clazz,
+            @NotNull String name,
+            @NotNull Class<?>[] parameterTypes
+    ) throws NoSuchMethodException {
+        return clazz.getDeclaredMethod(name, parameterTypes);
+    }
+
+    /**
+     * Instance is null on static method
+     */
+    public static Object invoke(
+            @NotNull Method method,
+            @Nullable Object instance,
+            @NotNull Object[] args
+    ) throws InvocationTargetException, IllegalAccessException {
+        return method.invoke(instance, args);
+    }
+}

src/main/kotlin/com/fasterxml/jackson/module/kotlin/ArgumentBucket.kt

@@ -0,0 +1,86 @@
+package com.fasterxml.jackson.module.kotlin
+
+import kotlin.reflect.KParameter
+
+internal class BucketGenerator(parameters: List<KParameter>) {
+    private val paramSize: Int = parameters.size
+    val maskSize = (paramSize / Int.SIZE_BITS) + 1
+    // For Optional and Primitive types, set the initial value because the function cannot be called if the argument is null.
+    private val originalValues: Array<Any?> = Array(paramSize) {
+        val param = parameters[it]
+
+        if (param.isOptional) {
+            ABSENT_VALUE[param.type.erasedType()]
+        } else {
+            null
+        }
+    }
+    private val originalMasks: IntArray = IntArray(maskSize) { FILLED_MASK }
+
+    fun generate() = ArgumentBucket(paramSize, originalValues.clone(), originalMasks.clone())
+
+    companion object {
+        private const val FILLED_MASK = -1
+
+        private val ABSENT_VALUE: Map<Class<*>, Any> = mapOf(
+            Boolean::class.javaPrimitiveType!! to false,
+            Char::class.javaPrimitiveType!! to Char.MIN_VALUE,
+            Byte::class.javaPrimitiveType!! to Byte.MIN_VALUE,
+            Short::class.javaPrimitiveType!! to Short.MIN_VALUE,
+            Int::class.javaPrimitiveType!! to Int.MIN_VALUE,
+            Long::class.javaPrimitiveType!! to Long.MIN_VALUE,
+            Float::class.javaPrimitiveType!! to Float.MIN_VALUE,
+            Double::class.javaPrimitiveType!! to Double.MIN_VALUE
+        )
+    }
+}
+
+/**
+ * Class for managing arguments and their initialization state.
+ * [masks] is used to manage the initialization state of arguments, and is also a mask to indicate whether to use default arguments in Kotlin.
+ * For the [masks] bit, 0 means initialized and 1 means uninitialized.
+ *
+ * @property  values  Arguments arranged in order in the manner of a bucket sort.
+ */
+internal class ArgumentBucket(
+    private val paramSize: Int,
+    val values: Array<Any?>,
+    private val masks: IntArray
+) {
+    private var initializedCount: Int = 0
+
+    private fun getMaskAddress(index: Int): Pair<Int, Int> = (index / Int.SIZE_BITS) to (index % Int.SIZE_BITS)
+
+    /**
+     * Set the argument. The second and subsequent inputs for the same `index` will be ignored.
+     */
+    operator fun set(index: Int, value: Any?) {
+        val maskAddress = getMaskAddress(index)
+
+        val updatedMask = masks[maskAddress.first] and BIT_FLAGS[maskAddress.second]
+
+        if (updatedMask != masks[maskAddress.first]) {
+            values[index] = value
+            masks[maskAddress.first] = updatedMask
+            initializedCount++
+        }
+    }
+
+    fun isFullInitialized(): Boolean = initializedCount == paramSize
+
+    /**
+     * An array of values to be used when making calls with default arguments.
+     * The null at the end is a marker for synthetic method.
+     * @return arrayOf(*values, *masks, null)
+     */
+    fun getValuesOnDefault(): Array<Any?> = values.copyOf(values.size + masks.size + 1).apply {
+        masks.forEachIndexed { i, mask ->
+            this[values.size + i] = mask
+        }
+    }
+
+    companion object {
+        // List of Int with only 1 bit enabled.
+        private val BIT_FLAGS: List<Int> = IntArray(Int.SIZE_BITS) { (1 shl it).inv() }.asList()
+    }
+}

src/main/kotlin/com/fasterxml/jackson/module/kotlin/ConstructorInstantiator.kt

@@ -0,0 +1,61 @@
+package com.fasterxml.jackson.module.kotlin
+
+import com.fasterxml.jackson.databind.DeserializationContext
+import com.fasterxml.jackson.databind.MapperFeature
+import com.fasterxml.jackson.module.kotlin.Instantiator.Companion.INT_PRIMITIVE_CLASS
+import java.lang.reflect.Constructor
+import kotlin.reflect.KFunction
+import kotlin.reflect.KParameter
+
+// This class does not support constructors for non-static inner classes.
+internal class ConstructorInstantiator<T>(
+    kConstructor: KFunction<T>, private val constructor: Constructor<T>
+) : Instantiator<T> {
+    // Top level constructor does not require any instance parameters.
+    override val hasInstanceParameter: Boolean = false
+    override val valueParameters: List<KParameter> = kConstructor.parameters
+    private val accessible: Boolean = constructor.isAccessible
+    private val bucketGenerator = BucketGenerator(valueParameters)
+    // This initialization process is heavy and will not be done until it is needed.
+    private val localConstructor: Constructor<T> by lazy {
+        val parameterTypes = arrayOf(
+            *constructor.parameterTypes,
+            *Array(bucketGenerator.maskSize) { INT_PRIMITIVE_CLASS },
+            DEFAULT_CONSTRUCTOR_MARKER
+        )
+
+        SpreadWrapper.getConstructor(constructor.declaringClass, parameterTypes)
+            .apply { isAccessible = true }
+    }
+
+    init {
+        // Preserve the initial value of Accessibility, and make the entity Accessible.
+        constructor.isAccessible = true
+    }
+
+    override fun checkAccessibility(ctxt: DeserializationContext) {
+        if ((!accessible && ctxt.config.isEnabled(MapperFeature.CAN_OVERRIDE_ACCESS_MODIFIERS)) ||
+            (accessible && ctxt.config.isEnabled(MapperFeature.OVERRIDE_PUBLIC_ACCESS_MODIFIERS))) {
+            return
+        }
+
+        throw IllegalAccessException("Cannot access to Constructor, instead found ${constructor.declaringClass.name}")
+    }
+
+    override fun generateBucket() = bucketGenerator.generate()
+
+    override fun callBy(bucket: ArgumentBucket): T = when (bucket.isFullInitialized()) {
+        true -> SpreadWrapper.newInstance(constructor, bucket.values)
+        false -> SpreadWrapper.newInstance(localConstructor, bucket.getValuesOnDefault())
+    }
+
+    companion object {
+        private val DEFAULT_CONSTRUCTOR_MARKER: Class<*> = try {
+            Class.forName("kotlin.jvm.internal.DefaultConstructorMarker")
+        } catch (ex: ClassNotFoundException) {
+            throw IllegalStateException(
+                "DefaultConstructorMarker not on classpath. Make sure the Kotlin stdlib is on the classpath."
+            )
+        }
+    }
+}

src/main/kotlin/com/fasterxml/jackson/module/kotlin/Instantiator.kt

@@ -0,0 +1,34 @@
+package com.fasterxml.jackson.module.kotlin
+
+import com.fasterxml.jackson.databind.DeserializationContext
+import kotlin.reflect.KParameter
+
+internal interface Instantiator<T> {
+    val hasInstanceParameter: Boolean
+
+    /**
+     * ValueParameters of the KFunction to be called.
+     */
+    val valueParameters: List<KParameter>
+
+    /**
+     * Checking process to see if access from context is possible.
+     * @throws  IllegalAccessException
+     */
+    fun checkAccessibility(ctxt: DeserializationContext)
+
+    /**
+     * The process of getting the target bucket to set the value.
+     */
+    fun generateBucket(): ArgumentBucket
+
+    /**
+     * Function call from bucket.
+     * If there are uninitialized arguments, the call is made using the default function.
+     */
+    fun callBy(bucket: ArgumentBucket): T
+
+    companion object {
+        val INT_PRIMITIVE_CLASS: Class<Int> = Int::class.javaPrimitiveType!!
+    }
+}

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinFeature.kt

@@ -1,12 +1,12 @@
 package com.fasterxml.jackson.module.kotlin
 
-import java.util.BitSet
+import java.util.*
 import kotlin.math.pow
 
 /**
  * @see KotlinModule.Builder
  */
-enum class KotlinFeature(private val enabledByDefault: Boolean) {
+enum class KotlinFeature(internal val enabledByDefault: Boolean) {
     /**
      * This feature represents whether to deserialize `null` values for collection properties as empty collections.
      */
@@ -42,7 +42,9 @@ enum class KotlinFeature(private val enabledByDefault: Boolean) {
      * may contain null values after deserialization.
      * Enabling it protects against this but has significant performance impact.
      */
-    StrictNullChecks(enabledByDefault = false);
+    StrictNullChecks(enabledByDefault = false),
+
+    ExperimentalDeserializationBackend(enabledByDefault = false);
 
     internal val bitSet: BitSet = 2.0.pow(ordinal).toInt().toBitSet()
 

src/main/kotlin/com/fasterxml/jackson/module/kotlin/KotlinModule.kt

@@ -2,13 +2,10 @@ package com.fasterxml.jackson.module.kotlin
 
 import com.fasterxml.jackson.databind.MapperFeature
 import com.fasterxml.jackson.databind.module.SimpleModule
-import com.fasterxml.jackson.module.kotlin.KotlinFeature.NullIsSameAsDefault
-import com.fasterxml.jackson.module.kotlin.KotlinFeature.NullToEmptyCollection
-import com.fasterxml.jackson.module.kotlin.KotlinFeature.NullToEmptyMap
-import com.fasterxml.jackson.module.kotlin.KotlinFeature.StrictNullChecks
+import com.fasterxml.jackson.module.kotlin.KotlinFeature.*
 import com.fasterxml.jackson.module.kotlin.SingletonSupport.CANONICALIZE
 import com.fasterxml.jackson.module.kotlin.SingletonSupport.DISABLED
-import java.util.BitSet
+import java.util.*
 import kotlin.reflect.KClass
 
 private const val metadataFqName = "kotlin.Metadata"
@@ -31,6 +28,9 @@ fun Class<*>.isKotlinClass(): Boolean {
  *                                      the default, collections which are typed to disallow null members
  *                                      (e.g. List<String>) may contain null values after deserialization.  Enabling it
  *                                      protects against this but has significant performance impact.
+ * @param   experimentalDeserializationBackend
+ *                                  Default: false.  Whether to enable experimental deserialization backend.  Enabling
+ *                                      it significantly improve performance in certain use cases.
  */
 class KotlinModule @Deprecated(
     level = DeprecationLevel.WARNING,
@@ -52,7 +52,8 @@ class KotlinModule @Deprecated(
     val nullToEmptyMap: Boolean = false,
     val nullIsSameAsDefault: Boolean = false,
     val singletonSupport: SingletonSupport = DISABLED,
-    val strictNullChecks: Boolean = false
+    val strictNullChecks: Boolean = false,
+    val experimentalDeserializationBackend: Boolean = false
 ) : SimpleModule(KotlinModule::class.java.name, PackageVersion.VERSION) {
     @Deprecated(level = DeprecationLevel.HIDDEN, message = "For ABI compatibility")
     constructor(
@@ -91,7 +92,8 @@ class KotlinModule @Deprecated(
             builder.isEnabled(KotlinFeature.SingletonSupport) -> CANONICALIZE
             else -> DISABLED
         },
-        builder.isEnabled(StrictNullChecks)
+        builder.isEnabled(StrictNullChecks),
+        builder.isEnabled(KotlinFeature.ExperimentalDeserializationBackend)
     )
 
     companion object {
@@ -109,7 +111,14 @@ class KotlinModule @Deprecated(
 
         val cache = ReflectionCache(reflectionCacheSize)
 
-        context.addValueInstantiators(KotlinInstantiators(cache, nullToEmptyCollection, nullToEmptyMap, nullIsSameAsDefault, strictNullChecks))
+        context.addValueInstantiators(KotlinInstantiators(
+            cache,
+            nullToEmptyCollection,
+            nullToEmptyMap,
+            nullIsSameAsDefault,
+            strictNullChecks,
+            experimentalDeserializationBackend
+        ))
 
         when (singletonSupport) {
             DISABLED -> Unit