HTTP GET/POST Requests

Let us focus on dealing with GET and POST request from web applications using the HTTP protocol directly (without Leonardo).

Receiving GET requests

To receive and handle a GET requests. Let us consider a Jolie program that supports the sum of two numbers, x and y, by means of an operation called sum.

execution { concurrent }

type SumRequest:void {
    .x:int
    .y:int
}

interface SumInterface {
    RequestResponse: sum(SumRequest)(int)
}

inputPort MyInput {
    Location: "socket://localhost:8000/"
    Protocol: http
    Interfaces: SumInterface
}

main
{
    sum( request )( response ) {
    response = request.x + request.y
    }
}

Jolie transparently supports the reception of GET requests ad the automatic parsing of HTTP query string. Hence, we can simply execute jolie sum.ol and point the browser to: http://localhost:8000/sum?x=6&y=2 to obtain the result of the sum computed by the code in our example.

Sending GET requests

The sum service can be invoked from another Jolie program using a HTTP GET request. We can do this with the following client code:

include "console.iol"

type SumRequest:void {
    .x:int
    .y:int
}

interface SumInterface {
    RequestResponse: sum(SumRequest)(int)
}

outputPort SumService {
    Location: "socket://localhost:8000/"
    Protocol: http { .method = "get" }
    Interfaces: SumInterface
}

main
{
    request.x = 4;
    request.y = 2;
    sum@SumService( request )( response );
    println@Console( response )()
}

We use the method parameter of HTTP protocol to set our request method to GET.

Receiving POST requests

Handling POST requests is similar to handling GET ones. Let us reuse the code given before for the sum service submitting a POST request: Jolie HTTP protocol implementation automatically detects a POST call and convert it to a standard message. Since POST calls are usually sent by browsers through HTML forms, we provide one by a simple extension of our sum service:

execution { concurrent }

type SumRequest:void {
    .x:int
    .y:int
}

interface SumInterface {
RequestResponse:
    sum(SumRequest)(int),
    form(void)(string)
}

inputPort MyInput {
    Location: "socket://localhost:8000/"
    Protocol: http { .format = "html" }
    Interfaces: SumInterface
}

main
{
    [ sum( request )( response ) {
        response = request.x + request.y
    }]{ nullProcess }

    [ form()( f ) {
        f = "
            <html>
            <body>
            <form action='sum' method='POST'>
                <code>x</code>: <input type='text' value='3' name='x' />
                <br/>
                <code>y</code>: <input type='text' value='2' name='y' />
                <br/>
                <input type='submit'/>
            </form>
            </body>
            </html>"
    }]{ nullProcess }
}

This time we use the format = "html" HTTP parameter to support the dispatch of HTML responses by operation form which returns an HTML page containing a form that targets the sum operation. After executing the code and pointing the browser to http://localhost:8000/form, we should see an HTML form that submits the values x and y to operation sum and gets back a result.

Sending POST requests

The difference between sending GET and POST requests stands in setting the method parameter. Let us modify the previous code used to shown how to send GET requests:

include "console.iol"

type SumRequest:void {
    .x:int
    .y:int
}

interface SumInterface {
    RequestResponse: sum(SumRequest)(int)
}

outputPort SumService {
    Location: "socket://localhost:8000/"
    Protocol: http { .method = "post" }
    Interfaces: SumInterface
}

main
{
    request.x = 4;
    request.y = 2;
    sum@SumService( request )( response );
    println@Console( response )()
}

Checking the message content

Use --trace for checking the http message sent, like in the following example:

jolie --trace yourclient-filename.ol

Formatting the request

By default, the request is not sent in json format. In order to specify that the payload must be a json, add parameter format to the http protocol as it follows:

outputPort SumService {
    Location: "socket://localhost:8000/"
    Protocol: http {
       .method = "post"
       .format = "json"
    }
    Interfaces: SumInterface
}

Jolie Documentation