IBM API Connect Sample Gateway scripts In this article we provide simple sample of gateway script useful for IBM API Connect

Introduction

Two programing languages: XSLT and GatewayScript

Why coding?

Useful links to official documentation: Using context variables in GatewayScript and XSLT policies with the DataPower API Gateway

API Connect context variables

OAuth context variables

Guidelines

Don't

Use carefully the different tools such as Existing policies, Global Policies, User Defined Policies, and code within an API. Another aspect is do I need to use a piece of code or default policies

Do

Useful tips

Automation

Returns a simple JSON message in the response

context.message.header.set('Content-Type', 'application/json');
context.message.body.write({"msg": "hello"});

Manipulate parameters

As described in the documentation (see links at the beginning of this article). Parameters are described with 2 information: the locations and the values. In the assembly you get access to the parameters using the context.request.parameters object. This gives you a structure containing arrays for both the locations and values. (This is normal and follows HTTP specifications). Let's take a simple sample, an operation with GET HTTP verb that has 2 query parameters name_to_return and param2. The object (for more clarity, not represented as JSON here but instead extracted from the step by step debugger) give this:

parameters: Object
	name_to_return: Object
		locations: Array(1)
			0: "query"
		values: Array(1)
				0: "Foo"
	param2: Object
		locations: Array(1)
			0: "query"
		values: Array(1)
			0: "Value2"

So to get access to the value of the name_to_return parameter (assuming only one parameter with this name), I simply use the following code:

var namet = context.request.parameters.name_to_return.values[0];

I can get access to the locations of this parameter (assuming only one parameter with this name)

var namel = context.request.parameters.name_to_return.locations[0];

Manipulate JSON structure

• First line create a string
• Second line create a JSON object
• Third line, append the JSON object

var fmsg= "hello " + namet;
var rt= {"msg": fmsg};
rt.msg2 = "msg2_value";

Manipulate headers

Add a custom header for the response

context.message.header.set('my-header1', 'my-h1-value');

Propagate Authorization header

var au = context.request.header.get('Authorization');
context.message.header.set('Authorization', au));

Write a message to the console

var all_apis = context.get('api');
console.error('>>> all_apis: ' + JSON.stringify(all_apis));

Manipulate context Variable

var clientID = context.get('client.app.id');
context.message.header.set('mycid', clientID);

Perform URI mapping

In this sample we specify a small piece of code where we remove the base path in order to invoke the backend API. There is small gateway script to specify the new path based on the request.path

var rpath = context.get('request.path');
var bpath = context.get('api.root');
var dest_path = rpath.substr(bpath.length + 1);
context.set('dest_path', dest_path);

In the invoke you can use this variable like this: $(target-url)$(dest_path)