我正在使用 https://templates.prediction.io/PredictionIO/template-scala-parallel-complementarypurchase 模板的 prediction.io，并通过 PHP-SDK 插入购买事件。
引擎已成功部署，但在查询时出现错误
curl -k -H "Content-Type: application/json" -d '{ "items": ["<item_id>"], "num": "3" }' https://localhost:8000/queries.json错误信息如下
Stack Trace:java.lang.RuntimeException: Unable to invoke no-args constructor for scala.collection.immutable.Set<java.lang.String>. Register an InstanceCreator with Gson for this type may fix this problem. at com.google.gson.internal.ConstructorConstructor$12.construct(ConstructorConstructor.java:210) at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:162) at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93) at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172) at com.google.gson.Gson.fromJson(Gson.java:803) at com.google.gson.Gson.fromJson(Gson.java:768) at com.google.gson.Gson.fromJson(Gson.java:717) at com.google.gson.Gson.fromJson(Gson.java:689) at io.prediction.workflow.JsonExtractor$.extractWithGson(JsonExtractor.scala:152) at io.prediction.workflow.JsonExtractor$.extract(JsonExtractor.scala:70) at io.prediction.workflow.ServerActor$$anonfun$24.apply(CreateServer.scala:519) at io.prediction.workflow.ServerActor$$anonfun$24.apply(CreateServer.scala:513) at spray.routing.ApplyConverterInstances$$anon$22$$anonfun$apply$1.apply(ApplyConverterInstances.scala:25) at spray.routing.ApplyConverterInstances$$anon$22$$anonfun$apply$1.apply(ApplyConverterInstances.scala:24) at spray.routing.ConjunctionMagnet$$anon$1$$anon$2$$anonfun$happly$1$$anonfun$apply$1.apply(Directive.scala:38) at spray.routing.ConjunctionMagnet$$anon$1$$anon$2$$anonfun$happly$1$$anonfun$apply$1.apply(Directive.scala:37) at spray.routing.directives.BasicDirectives$$anon$1.happly(BasicDirectives.scala:26) at spray.routing.ConjunctionMagnet$$anon$1$$anon$2$$anonfun$happly$1.apply(Directive.scala:37) at spray.routing.ConjunctionMagnet$$anon$1$$anon$2$$anonfun$happly$1.apply(Directive.scala:36) at spray.routing.directives.BasicDirectives$$anon$2.happly(BasicDirectives.scala:79) at spray.routing.Directive$$anon$7$$anonfun$happly$4.apply(Directive.scala:86) at spray.routing.Directive$$anon$7$$anonfun$happly$4.apply(Directive.scala:86) at spray.routing.directives.BasicDirectives$$anon$3$$anonfun$happly$1.apply(BasicDirectives.scala:92) at spray.routing.directives.BasicDirectives$$anon$3$$anonfun$happly$1.apply(BasicDirectives.scala:92) at spray.routing.directives.ExecutionDirectives$$anonfun$detach$1$$anonfun$apply$7$$anonfun$apply$3.apply$mcV$sp(ExecutionDirectives.scala:89) at spray.routing.directives.ExecutionDirectives$$anonfun$detach$1$$anonfun$apply$7$$anonfun$apply$3.apply(ExecutionDirectives.scala:89) at spray.routing.directives.ExecutionDirectives$$anonfun$detach$1$$anonfun$apply$7$$anonfun$apply$3.apply(ExecutionDirectives.scala:89) at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) at scala.concurrent.impl.ExecutionContextImpl$$anon$3.exec(ExecutionContextImpl.scala:107) at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.google.gson.internal.UnsafeAllocator$1.newInstance(UnsafeAllocator.java:48) at com.google.gson.internal.ConstructorConstructor$12.construct(ConstructorConstructor.java:207) ... 33 moreCaused by: java.lang.InstantiationException: scala.collection.immutable.Set at sun.misc.Unsafe.allocateInstance(Native Method) ... 39 more这是我的 engine.json
{ "id": "default", "description": "Default settings", "engineFactory": "com.my.ComplementaryPurchaseEngine", "datasource": { "params" : { "appName": "store", "eventNames": ["buy"] } }, "algorithms": [ { "name": "algo", "params": { "basketWindow" : 120, "maxRuleLength" : 2, "minSupport": 0.001, "minConfidence": 0.1, "minLift" : 1.0, "minBasketSize" : 2, "maxNumRulesPerCond": 5, "eventNames": ["buy"] } } ]}回答：
在您的 curl 请求中，num 字段不需要引号
curl -k -H "Content-Type: application/json" -d '{ "items": ["<item_id>"], "num": 3 }' https://localhost:8000/queries.json