Merge pull request #886 from vdebergue/json-error-performance

Improve performance of json lookups in case of errors

benchmarks/src/main/scala/play/api/libs/json/JsLookupBench.scala

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) from 2022 The Play Framework Contributors <https://github.com/playframework>, 2011-2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package play.api.libs.json
+
+import org.openjdk.jmh.annotations._
+
+import java.util.concurrent.TimeUnit
+
+@Warmup(iterations = 20, time = 1, timeUnit = TimeUnit.SECONDS)
+@Measurement(iterations = 10, time = 1, timeUnit = TimeUnit.SECONDS)
+@State(Scope.Benchmark)
+@BenchmarkMode(Array(Mode.Throughput))
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@Fork(
+  jvmArgsAppend =
+    Array("-Xmx350m", "-XX:+HeapDumpOnOutOfMemoryError", "-XX:-BackgroundCompilation", "-XX:-TieredCompilation"),
+  value = 1
+)
+class JsLookupBench {
+  @Param(Array("1", "20", "100"))
+  var size: Int                  = _
+  private var jsObject: JsObject = _
+
+  @Setup def setup(): Unit = {
+    jsObject = JsObject(0.until(size).map(i => i.toString -> JsString(s"This is my content for index $i")))
+  }
+
+  @Benchmark
+  def goodLookup: Option[String] = (jsObject \ (size - 1).toString).asOpt[String]
+
+  @Benchmark
+  def badLookup: Option[String] = (jsObject \ (size + 1).toString).asOpt[String]
+}

benchmarks/src/main/scala/play/api/libs/json/JsObjectBench.scala

@@ -1,3 +1,7 @@
+/*
+ * Copyright (C) from 2022 The Play Framework Contributors <https://github.com/playframework>, 2011-2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
 package play.api.libs.json
 
 import org.openjdk.jmh.annotations._

play-json/shared/src/main/scala/play/api/libs/json/JsLookup.scala

@@ -104,7 +104,9 @@ case class JsLookup(result: JsLookupResult) extends AnyVal {
       obj.underlying
         .get(fieldName)
         .map(JsDefined.apply)
-        .getOrElse(JsUndefined(s"'$fieldName' is undefined on object: $obj"))
+        .getOrElse(
+          JsUndefined(s"'$fieldName' is undefined on object. Available keys are ${obj.keys.mkString("'", "', '", "'")}")
+        )
     case JsDefined(o) =>
       JsUndefined(s"$o is not an object")
     case undef => undef