Simple example of how to use dispatch to access the. Simple examples a list of simple scala snippets, useful to understand some basics of the language, as well as to see what scala code looks like. We used the validate method for conversion which will rely on our implicit readsplace. To run an external command, follow it with an exclamation mark find project name. It should not be used for new projects, and is nor maintained. Im having trouble making a post request with a json object using dispatch and scala.
Contribute to jrudolphjson lenses development by creating an account on github. Scala includes a process library to simplify working with external processes. However, note that it handles timeouts very poorly, such as if the web service youre calling is down or running slowly. Scala using json andor xml templates stack overflow. This functionality depends on a converter of type writest which can convert a t to a jsvalue. For example, heres a way to create a dataset of 100 integers in a notebook. The examples repository contains the source code for several example lift applications, including demo building lift. How do i make these line of codes more scala ish shorter. 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. The previous tutorial covered basic xml processing in scala, but as i noted, xml is not the primary choice for data serialization these days. You want to generate a json representation of a scala object that contains one or more collections, such as a person class that has a list of friends or. So, here are some notes to help others navigate the scala json parsing landscape, where ther.
Jsonobject scala examples the following examples show how to use org. Overview in this article, we will discuss parse load large json files using jackson streaming apis. Working with json in scala using the json4s library part two working with json in scala using the json4s library part one. First, for primitive types in examples or demos, you can create datasets within a scala or python notebook or in your sample spark application. Community usage examples post a form using the synchronous backend get and parse json using the akka. I used the json smart cache library to do the actual parsing its really fast.
Working with json in scala using the json4s library part. Scalajson library, currently provides two minimal implementations of json ast, one that is designed for typical use and another that is designed for performancecorner cases. Jackson provides facility to improve application performance by using its streaming api which. Thus dispatch s json extraction occurs fundamentally in extractor objects that can implicitly convert to function objects. Even if the code that implements these operations is crappy it has happened before.
Scala parser combinators are a powerful way to build parsers that can be used in everyday programs. 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. While both encoders and standard serialization are responsible for turning an object into bytes, encoders are code generated dynamically and use a format that allows spark to perform many. Dispatch contribute to cb372 dispatch example development by creating an account on github. Simply put, using templating systems such as xml builder or jsonbuilder ht. According to the json specification not all of the defined json value types are allowed at the root level of a json document.
Crockford angry, you could maybe make a recursive function that pattern match against the json structures and do depthfirst traversal and returning the xml node on the function call. At this moment there are at least 6 json libraries for scala, not counting the java json libraries. How to create json strings from scala classes that have. It uses a json specific bodyparser which will parse the request and provide request.
A scala implementation of the rfc6901, rfc6902, and rfc7396. Using json with play and scala using json with javas play framework and scala is a natural fit. Json basics introduced reads and writes converters which are used to convert between jsvalue structures and other data types. Apache spark sql loading and saving data using the json.
Introduction to the scala parser and combinators dzone java. I define a string named json, which contains my json content. I ran a few tests last night in the scala repl to see if i could think of different ways to download the contents of a url to a string or file in scala, and came up with a couple of different solutions, which ill share here. August 11, 2014 4 minutes read christoph hartmann scala.
Would have saved me a day or two of trying them all out especially play json and json4s if had found this earlier. Youre working outside of a specific framework, and want to create a json string from a scala object. The following example demonstrates the parsing of json data into a predefined case class. Written evan chan 1172014 software development we were working on a spark job to read json files out of hdfs, and it seemed to be running way too slowly. Format of the data being exchanged example, plain text, json, csv. But i would recommend you use a better json library. This simple json example is based on a morecomplicated json example here at. The post request works fine for sure since i tested it using curl. Fwiw, heres an old approach i used to retrieve rest content content from a rest url. Normally, scala symbols can be thought of as a unique identifier which will always be the same. Post request with json in dispatch and scala stack overflow. Sjson supports serialization of scala objects into json. Sep 18, 2012 luckily, its easy to create a better and faster parser.
A json string for example like foo does not constitute a legal json document by itself. How do i download the contents of a url to a string or file in scala. There are many potential solutions to this problem. Datasets are similar to rdds, however, instead of using java serialization or kryo they use a specialized encoder to serialize the objects for processing or transmitting over the network. Sjson is available as an apache 2 licensed project on github here.
At this moment the approach taken to working with the ast has been taken from lift json and the native package is in. I am using scalatra, but this question should be valid for any scala programming. This project is a toolkit for working with json in scala that is based on example code from programming in scala by martin odersky, lex spoon, and bill venners. If you want to parse xml or json, you could snakk it instead.
I still get the java feeling in it which i want to stay away from. Accessing the heroku rest api via dispatch dzone java. It also provides methods to compute diffs between two json values that produce valid json patches or merge patches note. I parseextract that json string into an instance of my mailserver class. It implements support for built in scala structures like list, map or string as well as custom objects. Dynamic cache which allows us to handle arbitrary method calls. Read on to find out how you can enable and use json in your next play project.
Being a relative newcomer to scala i realize there are probably other, better ways to do this. If you know scala and are familiar with json, there isnt much to say about this example. Simple example of processing twitter json payload from a. 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. Dispatch defines lots of handlers that do a conversion behind the scenes into different types of data which you can then pass to block to work with. Theres nothing else thats special about them from scala s point of view. This page covers in greater detail how to build these converters and how to use validation during conversion. For example, using the library that comes with the play. In the latter example, because the type argument is erased as part of compilation.
These examples are extracted from open source projects. Chapter 10 of scala by example provides an explanation that is both gentle and comprehensive. This is an excerpt from the scala cookbook partially modified for the internet. How to get content from a rest url get rest content. Lots of web services and server backends now expect requests to be formatted as json.
The newman dsl was inspired by the dispatch library, but uses. Spark sql with scala using valid json input source example in. It turns out that the situation is similar if not worse read more. A quick tour of json libraries in scala manuel bernhardt. Simple example of how to use dispatch to access the chronicling america api asynchronously. Scala to jsvalue conversion is performed by the utility method json. The above example can be made even more concise by using body parsers with a typed validation function. However, dispatch json pimps out symbols making them json property extractors. If you simply want to use lift in your project, add lift as a dependency to your build system or download the jar files directly. Jan 06, 2016 spark sql with scala using valid json input source example in spark console spark sql with valid json input source.
Dataframes and datasets in apache spark ne scala 2016 duration. Scalapb can convert protocol buffers to and from json, using json4s. My impression is that most people using scala dont actually using scala. Subscribe to our newsletter and download the scala cookbook right. Finally figured this out after breaking my head over numerous scala json libraries that are not as performant or reliable as jackson. It provides a scala vocabulary for javas asyncclient. This step by step tutorial will explain how to create a spark project in scala with eclipse without maven and how. Quite often this requires the implementation of sdks for specific languages.
Mapstring, any extends jsontype with product with serializable. This project aims to provide a single ast to be used by other scala json libraries. You can relax this constraint by using the tolerantjson body parser. For more info, see the dispatch documentation site. This action expects a request with a contenttype header of text json or application json and a body containing a json representation of the entity to create. But its hard to understand the plumbing pieces and how to get started. Scala how to download url contents to a string or file. Working with json part 2 to see how we handle our json example as it evolves from containing a single movie to an array. Now that i have an extremely simple heroku app up and running see my previous post and dont know what to do with it, the logical next step for. In this tutorial we will learn how to parse json in java using jackson library. The play json api provides implicit writes for most basic types, such as int, double, string, and boolean. This is an example of how you might use the converter into your code. Sign in sign up instantly share code, notes, and snippets. Only json objects or json arrays are allowed as json document roots.