DATAMONGO-2138 - Type-safe Kotlin query extension

spring-data-mongodb/src/main/kotlin/org/springframework/data/mongodb/core/query/CriteriaExtensions.kt

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mongodb.core.query
 
+import kotlin.reflect.KProperty
+
 /**
  * Extension for [Criteria.is] providing an `isEqualTo` alias since `is` is a reserved keyword in Kotlin.
  *
@@ -38,3 +40,18 @@ fun <T: Any?> Criteria.inValues(c: Collection<T>) : Criteria = `in`(c)
  * @since 2.0
  */
 fun Criteria.inValues(vararg o: Any?) : Criteria = `in`(*o)
+
+/**
+ * Creates a Criteria using a KProperty as key.
+ * Supports nested field names with [NestedProperty].
+ * @author Tjeu Kayim
+ * @since 2.2
+ */
+fun where(key: KProperty<*>): Criteria = Criteria.where(nestedFieldName(key))
+/**
+ * Add new key to the criteria chain using a KProperty.
+ * Supports nested field names with [NestedProperty].
+ * @author Tjeu Kayim
+ * @since 2.2
+ */
+infix fun Criteria.and(key: KProperty<*>): Criteria = and(nestedFieldName(key))

spring-data-mongodb/src/main/kotlin/org/springframework/data/mongodb/core/query/NestedProperty.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.query
+
+import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty1
+
+/**
+ * Refer to a field in an embedded/nested document.
+ * @author Tjeu Kayim
+ * @since 2.2
+ */
+class NestedProperty<T, U>(
+	internal val parent: KProperty<U>,
+	internal val child: KProperty1<U, T>
+) : KProperty<T> by child
+
+/**
+ * Recursively construct field name for a nested property.
+ * @author Tjeu Kayim
+ */
+internal fun nestedFieldName(property: KProperty<*>): String {
+	return when (property) {
+		is NestedProperty<*, *> ->
+			"${nestedFieldName(property.parent)}.${property.child.name}"
+		else -> property.name
+	}
+}
+
+/**
+ * Builds [NestedProperty] from Property References.
+ * Refer to a field in an embedded/nested document.
+ *
+ * For example, referring to the field "book.author":
+ * ```
+ * Book::author / Author::name isEqualTo "Herman Melville"
+ * ```
+ * @author Tjeu Kayim
+ * @since 2.2
+ */
+operator fun <T, U> KProperty<T>.div(other: KProperty1<T, U>) =
+	NestedProperty(this, other)