Pointers to learn liftjson use outside lift the scala. Finally figured this out after breaking my head over numerous scala json libraries that are not as performant or reliable as jackson. Optics beyond lenses with monocle functional programming. At the moment, the list below is maintained for scala. Dear all, i am wondering, is there any helper class in scala which i can use for serializing and deserializing tofrom json objectsin string form. Working with a json is very common task in a software development process. To begin, lets briefly talk about the shape of every json object. I cant seem to write proper case classes for this particular json payload. Lift web framework minimal rest api example example. A very promising project started by the guys from wordnik of swagger fame, it aims to unify scala json asts, sports multiple backends including jackson, and has native support from both scalatra and spray. Working with json in scala using the json4s library part one.
I want to be able to gently handle failure in the response format, but it is becoming messy. In summary, if you need a scala json parsing example using the lift json library, i hope this example source code has been helpful. Creating a json string from a scala object problem youre working outside of a specific framework, and want to create a json string from a scala object. Lift json provides several different styles to extract data from json. Any valid json can be parsed into internal ast format. A protip by brianhsu about scala, rest, lift web fraemwork, and lift. Scala json library which has an automatic serialization by. Sep 18, 2012 luckily, its easy to create a better and faster parser. This implementation uses a threadsafe inmemory store. Working with json in scala can be as simple as in javascript. These examples are extracted from open source projects. I dont have anything else to add at this time, so ill leave it at that.
They are not according to crockfords original rfc 4627. Many scala libraries have been updated to be compatible with scala. Luckily, its easy to create a better and faster parser. How can i construct and parse a json string in scala lift. Scala to jsvalue conversion is performed by the utility method json. Ive read that the liftjson library is best for android apps, so im using dispatchliftjson. A quick tour of json libraries in scala manuel bernhardt. May 21, 2015 its extremely simple to learn and to work with, with only six or seven if you separate integers and doubles data types. Handling parsing failure in scala without exceptions.
Javas jackson does this, but it isnt native to scala. Jun 04, 2016 what follow is thus a way to build rest api in scala and not the way to build them. Its very useful to be familiar with this data type since its how circe models the base type we want to address. The reason why scala s json parsing mechanisms are so complex is because of type safety. Being a relative newcomer to scala i realize there are probably other, better ways to do this. This project also attempts to set lift json free from the release schedule imposed by the lift framework. Our json tutorial will help you to learn json fundamentals, example, syntax, array, object, encode, decode, file, date and date format. I followed these answers on stack overflow to find an easy way to parse json with scala, but it wasnt easy the only thing that ended up working for me was argonaut i just couldnt get the play json and lift json to work with sbt and intellj. Json might actually be a poor example because we know the output of a json parser to always emit regular structures, but this whole rigmarole is for type safety. I believe it has something to do with the first index in the array, which doesnt have a key string.
This simple json example is based on a morecomplicated json example here at. You need to parse these files and combine the data in two files to check how many asset impressions, views and clicks are present in both the files for each page view id. Can you please edit your question and show an example how you get such. One of the situations which could possibly push you against the wall is when you have classes extending traits. Its not just some incremental improvements over the status quo, it redefines the state of the art. My main problem with this is that its kind of ugly and unmanageable, exposes lots of the innards of how lift json is implemented, and the duplication of structure in the two case expressions. Json4s is one of the best libraries for manipulating json in scala. If you ever need to parse json stock data from using scala, heres a test class i just wrote that uses liftjson the json data format. Contributors implement that spec using various tech stacks. Handling parsing failure in scala without exceptions code. A protip by swartkrans about scala, btipling, and json. The todobackend project defines a simple web api spec for managing a todo list. This functionality depends on a converter of type writest which can convert a t to a jsvalue. Dynamic cache which allows us to handle arbitrary method calls.
It turns out that the situation is similar if not worse read more. Put up another blog post in my how to x in scala series. Android apps in scala, ios apps, and play framework web services. Easy json unmarshalling in scala with jackson example. What is the scalarific way to grab a value out of this json. Although json is so useful and ubiquitous, how is it that working with it is still a pain in the ass in scala. Here are some urls i used to get the correct lift json. Best regards, brian maso 949 3958551 brian at blumenfeldmaso dot. Javascript object notation is an open standard file format, and data interchange format, that. Im more used to working with json that represents objects see my other scala json examples but this data is more of an array of arrays format, so this approach is different than my. To quickly start using one of these libraries, just click on the dependency clipboard button to get the relevant sbt dependency definition. How to build fast and robust rest api with scala medium. Stack overflow for teams is a private, secure spot for you and your coworkers to find and share information. One such example is the ubiquitous onclicklistener interface.
In our codebase we came to a point where almost all workarounds were related to lift json until we switched to circe and everyone was. I have a really nested json very big and very deeply nested. The cost you pay in complexity pays dividends in type safety. One way to parse that is to map over child elements of the root json object. All i had to do in my scala code to make this work was define the emailaccount class as a case class. It provides a case class for each of the above mentioned json. How can i parse json text or a json document with scala. In scala you can do it in many ways, either with help of java popular libraries such as jackson or using scala specific libraries. Feb, 2017 converting a nested json document to csv using scala, hadoop, and apache spark posted on feb, 2017 at 6.
Rxjs, ggplot2, python data persistence, caffe2, pybrain, python data access, h2o, colab, theano, flutter, knime, mean. I used the json smart cache library to do the actual parsing its really fast. Json tutorial for beginners and professionals provides deep knowledge of json technology. Ive hear on this list that lift json is a good lib for parsingprocessingproducing json data. Run the specs view the code example implementation. Native deserialization 940 ms based on the lift web framework json parser jackson deserialization 670 ms. I will use code and terminology taken from monocle scala library for optics.
At this moment the approach taken to working with the ast has been taken from lift json and the native package is in fact lift json but outside of the lift project. This project aims to provide a single ast to be used by other scala json libraries. The most common method of using this interface in java is through an anonymous inner class. Scala json library which has an automatic serialization by introspection im looking for a good json library for scala that can serialize an arbitrary object graph to json, without requiring me to write mapping code.
Apk rcela isdoewdn jrpw jsraw jz rbcr tegq latacu ikccspitcr jc eddbedem jn. Liftweb json serialization and deserialization using scala. The play json api provides implicit writes for most basic types, such as int, double, string, and boolean. Feb 29, 2016 json4s is one of the best libraries for manipulating json in scala. The real comparison i can make is between lift and spray.
Jun 23, 2015 working with json in scala using the json4s library part two working with json in scala using the json4s library part one. An example that many readers have likely experienced is that of the gmail user interface. One of the things im doing here is to parse some of the json text into an array of objects, in this case an array of string objects. In particular, im trying to parse a json document into scala objects, and im using liftjson to do so. It allows for easy customization and is handy for writing and parsing json strings. Here are some examples and common use cases you may have come across and some you perhaps havent. Lift is the only new framework in the last four years to offer fresh and innovative approaches to web development. The lift json json parser in liftweb does a good job, too, but returns jobjectlike types instead of raw string or map. We use the awesome lift json library in quite a few our projects.
Common basic operations using jackson as backend last updated. Add following pimp to scope for instance into your package object. Resthelper resthelper is a trait provided by lift web framework, which let us create rest api in a simple and beautiful way there are already lots of example of resthelper, but i feel most of those example a little bit long, so ive created a really minimal json rest api of a blog article, which support get post and delete request. Scala reflection libraries, such as manifests and scala json libraries like liftjson. Read on to find out how you can enable and use json in your next play project. Json is the circe data type representing a json object.
As soon as you have a type class able to transform the scala type to json, it is pretty easy to generate any scala value to json. Here are some urls i used to get the correct lift json jar. Lift boldly won for my task because the api was much more straightforward and bugprone. Spark sql can automatically infer the schema of a json dataset and load it as a dataframe. A scala implementation using finch for web and circe for json. Todobackend a shared example to showcase backend tech stacks. Which framework to use for development of a rest api. Using json with play and scala using json with javas play framework and scala is a natural fit. Scala json library which has an automatic serialization. Each line must contain a separate, selfcontained valid json object. As i continue to plug away on my computer voice control. The source code is ugly i write now because i just got it working, but i thought id share it here in case you need to parse some json data thats in an array format like this.
But what is not that universally known is that there are more similar abstractions. The motivation of the new scala ast that has been proposed is to provide true interoperability between all libraries that talk in json across the scala language. There are many good json libraries for scala, the likes of sprayjson and json4s. If you have been a scala developer for some time now you are probably familiar with the concept of lenses. Jsonarray scala examples the following examples show how to use org. This package implements interoperability between lift json s ast and the scala json ast that is being proposed for inclusion in the scala language.
Lift json, shorttypehints and scala traits knoldus blogs. We are working on a scala project using play framework. This tutorial will walk you through how to work effectively with json data in scala, walking through a few common workflows on a piece of realworld json data. A simple scala json parsing example, using the lift framework lift json library. Working with json in scala using the json4s library part two. Currently using the lift json library need some help. A central concept in lift json library is json ast which models the structure of a json document as a syntax tree. Im trying to put together a collection of handson tutorials on how to do common things, not necessarily scala specific tasks, but using the scala language. Rxjs, ggplot2, python data persistence, caffe2, pybrain. Converting a nested json document to csv using scala, hadoop.
848 885 1238 375 285 795 609 1449 905 624 313 910 733 597 1409 749 302 826 1520 1240 583 658 49 1561 18 725 1429 1042 726 61 382 979 1109 1 1049 753 86 1434 786 1323 20 62 1021 1196 1237