Ballerina (programming language)

Ballerina

Designed by	Sanjiva Weerawarana, James Clark, Sameera Jayasoma, Hasitha Aravinda, Srinath Perera, Frank Leymann and WSO2 [1]
Developer	WSO2
First appeared	2017;7 years ago (2017)
Typing discipline	Structural, strong, static, inferred
Implementation language	Java, Ballerina, TypeScript [2]
OS	Cross-platform
License	Apache License 2.0 [3]
Website	ballerina.io
Influenced by
Java, Javascript, Go, Rust, C# [4]

Ballerina is an open source general-purpose programming language designed by WSO2 for cloud-era application programmers. ^[2]

The project started in 2015 by architects from WSO2 as a code-based alternative to the configuration-based integration tools such as EAI, ESB, and workflow products. ^{[5] [6]}

It has various constructs geared toward cloud-native development including support for various data formats and protocols, reliability, distributed transactions, APIs, and event streams. ^{[7] [8] [9]}

History

Ballerina was first publicly announced in 2017 and version 1.0 was released on September 10, 2019. ^[10]

Design

Ballerina is a general-purpose language with a familiar syntax along with a direct graphical representation of the code in the form of sequence diagrams. It has fundamental abstractions designed to make integration problems easier to program. ^[11] Ballerina was designed by WSO2 to improve productivity for application developers that have to work with distributed computing. It is easy to write and modify and is suitable for application programmers. ^{[12] [13] [14]}

The designers, who provided enterprise integration products for over 10 years, used their knowledge of the industry when designing the language, ^{[15] [16]} says WSO2 director and Ballerina founder James Clark.

Examples

Hello World

The regular Hello World program:

importballerina/io;publicfunctionmain(){io:println("Hello World!");}

To execute the above program, place the source code in a .bal file and provide the path of the file to the bal run command.

$ ballerinarunhello_world.bal Hello World!

The service version of the Hello World program:

import ballerina/http;  service /greet on new http:Listener(9090) {     resource function get . () returns string {         return "Hello World!";     } } 

Services are executed in the same manner, except they don't terminate like regular programs do. Once the service is up and running, one can use an HTTP client to invoke the service. For example, the above service can be invoked using the following cURL command:

$ curlhttp://localhost:9090/greetHello World!

^[17]

REST API

importballerina/http;serviceonnewhttp:Listener(9090){resourcefunctionpostfactorial(@http:Payloadstringpayload)returnshttp:Ok|http:BadRequest{int|errornum=int:fromString(payload);ifnumiserror{return<http:BadRequest>{body:"Invalid integer: "+payload};}ifnum<0{return<http:BadRequest>{body:"Integer should be >= 0"};}intresult=1;foreachintiin2...num{result*=i;}return<http:Ok>{body:result};}}

$ curlhttp://localhost:9090/factorial-d5120

GraphQL API

importballerina/graphql;service/stocksonnewgraphql:Listener(4000){resourcefunctiongetquote()returnsStockQuote{return{ticker:"EXPO",price:287.5,open:285,prevClose:285.5,low:276.25,high:297};}}typeStockQuoterecord{|stringticker;floatprice;floatopen;floatprevClose;floatlow;floathigh;|};

$ curl-H"Content-type: application/json"-d'{"query": "{ quote { ticker, price } }" }''http://localhost:4000/stocks'{"data":{"quote":{"ticker":"EXPO", "price":287.5}}}

Sequence diagram

The generated sequence diagram is a canonical representation of the source code. The two representations can be used interchangeably. The diagram support is provided through the Ballerina VS Code plugin. The following are a couple of such generated sequence diagrams, compared with its associated code.

A sample program for retrieving and processing COVID-19 data:

A sample program for creating a report out of pull request data retrieved from GitHub:

JSON support

The language provides support for working with JSON values. The builtin type `json` is defined as the following union: ()|boolean|int|float|decimal|string|json[]|map<json>

importballerina/io;publicfunctionmain()returnserror{// Syntax for `json` object values is very similar to the syntax of JSONjsonperson={name:"John Doe",age:25};// Serialized `json` values conforms to the JSON specification io:println(person);// The fields of the `json` value can be accessed as followsstringname=checkperson.name;intage=checkperson.age;}

Code to cloud

Docker and Kubernetes artifacts required for deploying the code to the cloud can be generated when building the code. Values required for these artifacts are derived from the code. Additionally, one can override these values as well using the Cloud.toml file. To enable generation of the cloud artifacts, the users can use the cloud build option in the Ballerina.toml file. Use docker to generate just the Docker image and the Dockerfile and use k8s to generate Kubernetes artifacts as well. Minimal sample config TOML files would look something like the following:

Ballerina.toml file:

[package]distribution="2201.0.0"[build-options]cloud="k8s"

Cloud.toml file:

[container.image]repository="bal_user"name="greet"tag="v0.1.0"

Workers

importballerina/http;importballerina/lang.'int;importballerina/io;// Workers interact with each other by sending and receiving messages.// Ballerina validates every worker interaction (send and receive)// to avoid deadlocks.publicfunctionmain(){@strand{thread:"any"}workerw1{intw1val=checkpaniccalculate("2*3");// Sends a message asynchronously to the worker `w2`.w1val->w2;// Receives a message from the worker `w2`.intw2val=<-w2;io:println("[w1] Message from w2: ",w2val);// Sends messages synchronously to the worker `w3`. The worker `w1` will wait// until the worker `w3` receives the message.w1val->>w3;w2val->w3;// Flushes all messages sent asynchronously to the worker `w3`. The worker// will halt at this point until all messages are sent or until the worker `w3`// fails.checkpanicflushw3;}// A worker can have an explicit return type, or else, if a return type is not mentioned,// it is equivalent to returning ().@strand{thread:"any"}workerw2{intw2val=checkpaniccalculate("17*5");// Receives a message from the worker `w1`.intw1val=<-w1;io:println("[w2] Message from w1: ",w1val);// Sends a message asynchronously to the worker `w1`.w1val+w2val->w1;}workerw3{int|errorw1val=<-w1;int|errorw2val=<-w1;io:println("[w3] Messages from w1: ",w1val,", ",w2val);}// Waits for the worker `w1`to finish.waitw1;}functioncalculate(stringexpr)returnsint|error{http:ClienthttpClient=checknew("https://api.mathjs.org");stringresponse=checkhttpClient->get(string`/v4/?expr=${expr}`);returncheck'int:fromString(response);}

^[18]

References

1. "Ballerina Language Specification". WSO2. Archived from the original on 2020-08-11. Retrieved 2020-04-24.
2. Open Source Contributors (18 June 2019). "Ballerina source code". GitHub.
3. "WSO2 / LICENSE". github.com. WSO2. 2017-03-08. Retrieved 2018-03-01.
4. "Ballerina, A modern programming language focused on integration" (PDF): 15.{{cite journal}}: Cite journal requires |journal= (help)
5. "Ballerina Microservices Programming Language: Introducing the Latest Release and "Ballerina Central"". InfoQ. Retrieved 2018-06-07.
6. Earls, Alan (2019-03-01). "How does Ballerina stack up as a cloud-native programming language?" . Retrieved 2019-07-23.
7. Doyle, Kerry. "10 of the best programming languages to learn in 2020" . Retrieved 2020-09-16.
8. Posta, Christian. "Evolution of Integration and Microservices with Service Mesh and Ballerina". YouTube . Retrieved 2019-07-24.
9. Techworld staff. "Top programming languages you should try". Techworld. Retrieved 2018-06-07.
10. "Ballerina Reinvents Cloud-Native Middleware as a Programming Language". GlobeNewswire (Press release). 10 September 2019. Retrieved 2020-09-16.
11. Ratnayake, Dakshitha. "Ballerina Swan Lake: 10 Compelling Language Characteristics for Cloud Native Programming". InfoQ. Retrieved 1 March 2022.
12. Jackson, Joab. "Ballerina: An API-First Programming Language". The New Stack. Retrieved 2018-06-11.
13. Foremski, Tom (2019-03-01). "Technology and the Arts: Celebrating Ballerina, a computer language of integration" . Retrieved 2019-07-14.
14. Lawton, George (2018-11-01). "Ballerina language promises to improve app integration" . Retrieved 2019-07-23.
15. Clark, James. "Ballerina Programming Language Part 0 - Context" . Retrieved 2020-09-16.
16. Clark, James. "Ballerina Programming Language Part 1 - Concepts" . Retrieved 2020-09-16.
17. Ballerina Team (16 September 2020). "Hello world service". ballerina.io. Archived from the original on 16 September 2020. Retrieved 16 September 2020.
18. Ballerina Team (16 September 2020). "Worker interaction". ballerina.io.

Further reading

• Fernando, Anjana, Warusawithana, Lakmal (2020) Beginning Ballerina Programming , Apress (part of Springer Nature)

External links

• https://ballerina.io
• https://github.com/ballerina-platform/ballerina-lang GitHub repository.