Ballerina (programming language)

History

Design

Examples

Hello World

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

$ ballerinarunhello_world.bal
Hello World!

importballerina/http;
service/greetonnewhttp:Listener(9090){
resourcefunctionget.()returnsstring{
return"Hello World!";
}
}

$ curlhttp://localhost:9090/greet
Hello World!

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-d5
120

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

JSON support

importballerina/io;
publicfunctionmain()returnserror{
// Syntax for `json` object values is very similar to the syntax of JSON
jsonperson={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 follows
stringname=checkperson.name;
intage=checkperson.age;
}

Code to cloud

[package]
distribution="220100"
[build-options]
cloud="k8s"

[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);
}

References

Further reading

External links